{"id":25339,"date":"2026-10-20T13:10:09","date_gmt":"2026-10-20T13:10:09","guid":{"rendered":"https:\/\/www.obd2tool.com\/blog\/?p=25339"},"modified":"2026-10-22T14:37:13","modified_gmt":"2026-10-22T14:37:13","slug":"caterpillar-311b-2ls-interference-fault-mid-122-cid-0269-fmi-03","status":"publish","type":"post","link":"https:\/\/www.obd2tool.com\/blog\/caterpillar-311b-2ls-interference-fault-mid-122-cid-0269-fmi-03\/","title":{"rendered":"Caterpillar 311B Excavator 2LS Interference Fault (MID 122 \u2013 CID 0269 \u2013 FMI 03): Symptoms and Test Solution"},"content":{"rendered":"<p><span data-preserver-spaces=\"true\">The Caterpillar 311B excavator may log a 2LS interference fault (MID 122 \u2013 CID 0269 \u2013 FMI 03). According to the supplied troubleshooting information, this diagnostic code indicates an abnormally high voltage in the sensor power supply circuit T930-WH-18.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">The circuit has a nominal voltage of 8.3 VDC. When the voltage exceeds the normal operating range, sensors connected to the supply may not function properly and may potentially be damaged.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">Possible causes include a short circuit between the sensor power supply and battery voltage, a faulty sensor, or, less commonly, a faulty Electronic Control Module (ECM).<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">This guide explains the fault description, possible causes, electrical testing procedures, expected results, and recommended repair actions.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Important:<\/span><\/strong><span data-preserver-spaces=\"true\"> Confirm the exact 2LS designation, circuit connections, connector pin assignments, and test specifications using the Caterpillar service documentation and electrical schematic applicable to the machine&#8217;s serial number.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-25341\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-311b-cid-0269-fmi-03-diagnostics.jpg\" alt=\"\" width=\"1024\" height=\"1024\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-311b-cid-0269-fmi-03-diagnostics.jpg 1024w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-311b-cid-0269-fmi-03-diagnostics-300x300.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-311b-cid-0269-fmi-03-diagnostics-900x900.jpg 900w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-311b-cid-0269-fmi-03-diagnostics-150x150.jpg 150w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-311b-cid-0269-fmi-03-diagnostics-768x768.jpg 768w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-311b-cid-0269-fmi-03-diagnostics-120x120.jpg 120w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/p>\n<h2><span data-preserver-spaces=\"true\">1. Fault Description: MID 122 \u2013 CID 0269 \u2013 FMI 03<\/span><\/h2>\n<p><span data-preserver-spaces=\"true\">The supplied diagnostic procedure identifies an overvoltage condition in the sensor power supply circuit T930-WH-18.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">The nominal supply voltage is 8.3 VDC. If the voltage rises above the specified range, the connected sensors may not operate correctly.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Understanding the Diagnostic Code<\/span><\/h3>\n<ul>\n<li><strong><span data-preserver-spaces=\"true\">MID 122:<\/span><\/strong><span data-preserver-spaces=\"true\"> Identifies the module reporting the diagnostic event in the applicable machine configuration.<\/span><\/li>\n<li><strong><span data-preserver-spaces=\"true\">CID 0269:<\/span><\/strong><span data-preserver-spaces=\"true\"> Identifies the component or circuit associated with the diagnostic code.<\/span><\/li>\n<li><strong><span data-preserver-spaces=\"true\">FMI 03:<\/span><\/strong><span data-preserver-spaces=\"true\"> Indicates voltage above normal or a short to a higher-voltage source.<\/span><\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-25342\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-311b-mid-122-cid-0269-fmi-03-fault-code.jpg\" alt=\"Caterpillar 311B MID 122 CID 0269 FMI 03 fault code infographic showing the T930-WH-18 sensor power supply overvoltage condition\" width=\"1000\" height=\"563\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-311b-mid-122-cid-0269-fmi-03-fault-code.jpg 1000w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-311b-mid-122-cid-0269-fmi-03-fault-code-300x169.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-311b-mid-122-cid-0269-fmi-03-fault-code-900x507.jpg 900w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-311b-mid-122-cid-0269-fmi-03-fault-code-768x432.jpg 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/p>\n<p><span data-preserver-spaces=\"true\">Confirm the exact interpretation of the module and component identifiers against the applicable Caterpillar service information.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">For more information about reading and interpreting Caterpillar fault codes, see our <\/span><a class=\"editor-rtfLink\" href=\"https:\/\/www.obd2tool.com\/blog\/how-to-read-caterpillar-diagnostic-codes-a-comprehensive-guide\/\" target=\"_blank\" rel=\"noopener\"><span data-preserver-spaces=\"true\">Caterpillar Diagnostic Codes: A Comprehensive Guide<\/span><\/a><span data-preserver-spaces=\"true\">.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Common Fault Symptoms<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">Depending on the affected circuit and machine configuration, the following conditions may occur:<\/span><\/p>\n<ul>\n<li><span data-preserver-spaces=\"true\">MID 122 \u2013 CID 0269 \u2013 FMI 03 is logged.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Sensors connected to the affected power supply may not function correctly.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Related electronic monitoring or control functions may be affected.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">The fault may remain active or appear intermittently if the problem involves a poor connection or damaged wiring.<\/span><\/li>\n<\/ul>\n<p><span data-preserver-spaces=\"true\">The supplied diagnostic information also notes that if no sensors are connected to the power supply, the fault may be considered a tampering fault. In this situation, verify the machine configuration and follow the applicable Caterpillar diagnostic procedure before replacing components.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">2. Possible Causes of the 2LS Interference Fault<\/span><\/h2>\n<p><span data-preserver-spaces=\"true\">Before replacing a sensor or ECM, systematically inspect the electrical circuit.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Cause 1: Sensor Power Supply Shorted to Battery<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The T930-WH-18 sensor power supply wire may be contacting a battery-voltage circuit because of damaged insulation, pinched wiring, incorrect previous repairs, or connector damage.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">This is a primary possibility when the measured voltage exceeds the specified range.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Cause 2: Faulty Sensor<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">An external sensor connected to the affected power supply may be internally damaged or causing an abnormal electrical condition.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">If the initial supply and harness checks pass, investigate the connected sensors according to the machine&#8217;s electrical schematic and diagnostic procedure.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Cause 3: Damaged Product Link Harness<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The Product Link harness may contain damaged insulation or an internal short between the sensor supply circuit and battery power.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">The resistance test in Step 2 helps identify this possibility.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Cause 4: Machine Sensor Harness Short Circuit<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The machine sensor harness may also have a short between the sensor power supply circuit and a battery-voltage circuit.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">Inspect wiring branches, connectors, and exposed conductors for damage, abrasion, corrosion, or incorrect repairs.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Cause 5: Faulty ECM<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">An ECM fault is possible, but the supplied diagnostic procedure identifies it as unlikely.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">Do not replace the ECM until you have checked the wiring, power supply, connectors, and connected sensors, and completed the prescribed diagnostic procedure.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">3. Tools Required for Diagnosis<\/span><\/h2>\n<p><span data-preserver-spaces=\"true\">Prepare the following equipment before starting the tests:<\/span><\/p>\n<ul>\n<li><span data-preserver-spaces=\"true\">A digital multimeter capable of measuring DC voltage and resistance.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">The applicable Caterpillar electrical schematic and service manual.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">CAT ET diagnostic software.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">A compatible Caterpillar communication adapter.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Appropriate electrical test leads and connector tools.<\/span><\/li>\n<\/ul>\n<h3><span data-preserver-spaces=\"true\">Recommended Diagnostic Equipment<\/span><\/h3>\n<p><strong><span data-preserver-spaces=\"true\">CAT Communication Adapter III Diagnostic Kit<\/span><\/strong><\/p>\n<p><span data-preserver-spaces=\"true\">A compatible communication adapter allows CAT ET to communicate with supported Caterpillar electronic control modules.<\/span><\/p>\n<p><a class=\"editor-rtfLink\" href=\"https:\/\/www.obd2tool.com\/goods-2485-CAT-Caterpillar-ET-Diagnostic-Adapter-III-PLUS-laptop.html\" target=\"_blank\" rel=\"noopener\"><span data-preserver-spaces=\"true\">View CAT ET Diagnostic Adapter III with Laptop<\/span><\/a><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Caterpillar Electronic Technician (CAT ET) Software<\/span><\/strong><\/p>\n<p><span data-preserver-spaces=\"true\">CAT ET can retrieve supported diagnostic codes and help verify whether CID 0269 FMI 03 remains active after troubleshooting.<\/span><\/p>\n<p><a class=\"editor-rtfLink\" href=\"https:\/\/www.obd2tool.com\/goods-10449-Cat-Caterpillar-ET-Electronic-Technician-Diagnostic-Software.html\" target=\"_blank\" rel=\"noopener\"><span data-preserver-spaces=\"true\">View CAT Caterpillar ET Electronic Technician Diagnostic Software<\/span><\/a><\/p>\n<p><span data-preserver-spaces=\"true\">For help with the communication interface and software setup, read our <\/span><a class=\"editor-rtfLink\" href=\"https:\/\/www.obd2tool.com\/blog\/caterpillar-et-communication-adapter-3-guide\/\" target=\"_blank\" rel=\"noopener\"><span data-preserver-spaces=\"true\">CAT ET 2026B and Communication Adapter 3 Guide<\/span><\/a><span data-preserver-spaces=\"true\">.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Compatibility note:<\/span><\/strong><span data-preserver-spaces=\"true\"> Confirm the exact adapter model, part number, driver, software version, and machine application before purchasing. Communication adapter part numbers and supported functions vary.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">4. Test Step 1: Check the Sensor Power Output<\/span><\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-25343\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-sensor-power-supply-voltage-test.jpg\" alt=\"Technician measuring Caterpillar excavator sensor power supply voltage with a digital multimeter during CID 0269 FMI 03 troubleshooting\" width=\"829\" height=\"727\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-sensor-power-supply-voltage-test.jpg 829w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-sensor-power-supply-voltage-test-300x263.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-sensor-power-supply-voltage-test-768x674.jpg 768w\" sizes=\"auto, (max-width: 829px) 100vw, 829px\" \/><\/p>\n<p><span data-preserver-spaces=\"true\">First, determine whether the sensor power supply output is within the specified voltage limits.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Test Procedure<\/span><\/h3>\n<ol>\n<li><span data-preserver-spaces=\"true\">Turn the key start switch to the OFF position.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Disconnect the Product Link input\/output cable at connector J2 from the machine&#8217;s sensor cable, following the applicable service procedure.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">With the connector disconnected as specified, measure the sensor power output at J2-1.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Check the voltage with the key switch OFF.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Turn the key switch to the ON position and check the voltage again.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Use the reference point specified in the Caterpillar electrical schematic.<\/span><\/li>\n<\/ol>\n<h3><span data-preserver-spaces=\"true\">Expected Results<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">Key switch state Expected voltage<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">OFF Less than 4 VDC<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">ON Less than 9 VDC<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">The ON-state limit is consistent with investigating an overvoltage condition on a supply with a nominal voltage of 8.3 VDC.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result A: Voltage Is Within the Specified Range<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">If the OFF-state voltage is below 4 VDC and the ON-state voltage is below 9 VDC, the Product Link sensor power supply and Product Link harness may not be faulty.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">The machine sensor harness or an external sensor may be responsible for the problem.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Next step:<\/span><\/strong><span data-preserver-spaces=\"true\"> Proceed to Test Step 3.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result B: Voltage Is Outside the Specified Range<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">If the voltage does not meet the required limits, the Product Link harness may have a short to battery voltage.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Next step:<\/span><\/strong><span data-preserver-spaces=\"true\"> Proceed to Test Step 2.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">5. Test Step 2: Check the Product Link Harness for a Short to Battery<\/span><\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-25346\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-product-link-harness-resistance-test.jpg\" alt=\"Testing Caterpillar Product Link and machine sensor harness resistance for a short to battery during CID 0269 FMI 03 diagnosis\" width=\"1100\" height=\"743\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-product-link-harness-resistance-test.jpg 1100w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-product-link-harness-resistance-test-300x203.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-product-link-harness-resistance-test-900x608.jpg 900w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-product-link-harness-resistance-test-768x519.jpg 768w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/caterpillar-product-link-harness-resistance-test-120x80.jpg 120w\" sizes=\"auto, (max-width: 1100px) 100vw, 1100px\" \/><\/p>\n<p><span data-preserver-spaces=\"true\">This test checks whether the Product Link harness sensor power circuit is shorted to the battery power supply.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Test Procedure<\/span><\/h3>\n<ol>\n<li><span data-preserver-spaces=\"true\">Turn the key start switch to the OFF position.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Leave the Product Link input\/output cable and machine sensor cable disconnected.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Confirm the circuit is de-energized before measuring resistance.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">On the Product Link harness, measure resistance between the sensor power contact J2-1 (+V) and the Product Link cable battery power contact J1-1.<\/span><\/li>\n<\/ol>\n<h3><span data-preserver-spaces=\"true\">Expected Result<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The resistance should be <\/span><strong><span data-preserver-spaces=\"true\">greater than 5,000 ohms (5 k\u03a9)<\/span><\/strong><span data-preserver-spaces=\"true\">.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result A: Resistance Is Greater Than 5,000 Ohms<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The Product Link harness passes this resistance check for a short between the specified contacts.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Next step:<\/span><\/strong><span data-preserver-spaces=\"true\"> Proceed to Test Step 3.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result B: Resistance Is Not Greater Than 5,000 Ohms<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">A short circuit may exist between Product Link harness contact J2-1 (T930-WH-18) and battery power contact J1-1.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Repair procedure:<\/span><\/strong><\/p>\n<ul>\n<li><span data-preserver-spaces=\"true\">Inspect the Product Link harness for damaged insulation and exposed conductors.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Check connector terminals for corrosion, damage, or incorrect contact.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Repair the wiring according to the applicable Caterpillar procedure, or replace the faulty harness if necessary.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Repeat the prescribed electrical checks before reconnecting the system.<\/span><\/li>\n<\/ul>\n<h2><span data-preserver-spaces=\"true\">6. Test Step 3: Check the Machine Sensor Harness for a Short to Battery<\/span><\/h2>\n<p><span data-preserver-spaces=\"true\">If the Product Link harness passes its resistance check, inspect the machine sensor harness.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Test Procedure<\/span><\/h3>\n<ol>\n<li><span data-preserver-spaces=\"true\">Turn the key start switch to the OFF position.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Leave the Product Link input\/output cable and machine sensor cable disconnected as specified in the diagnostic procedure.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Confirm that the circuit is de-energized.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">On the machine sensor harness, measure resistance between the sensor power contact J2-1 (+V) and the battery power supply contact identified in the applicable electrical schematic.<\/span><\/li>\n<\/ol>\n<h3><span data-preserver-spaces=\"true\">Expected Result<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The resistance should be <\/span><strong><span data-preserver-spaces=\"true\">greater than 5,000 ohms (5 k\u03a9)<\/span><\/strong><span data-preserver-spaces=\"true\">.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result A: Resistance Is Greater Than 5,000 Ohms<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The machine sensor harness passes this resistance check for a short between the specified contacts.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">The connected sensor or another intermittent electrical fault may require further investigation.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Next step:<\/span><\/strong><span data-preserver-spaces=\"true\"> Proceed to Test Step 4.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result B: Resistance Is Not Greater Than 5,000 Ohms<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">A short circuit between the sensor power circuit and battery power is possible.<\/span><\/p>\n<p><strong><span data-preserver-spaces=\"true\">Repair procedure:<\/span><\/strong><\/p>\n<ul>\n<li><span data-preserver-spaces=\"true\">Inspect the machine sensor harness for damaged insulation, pinched wiring, and exposed conductors.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Check the connectors and wiring branches for unintended contact with battery-voltage circuits.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Repair or replace the affected wiring harness as required.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Repeat the prescribed electrical tests before reconnecting the system.<\/span><\/li>\n<\/ul>\n<p><span data-preserver-spaces=\"true\">A satisfactory resistance measurement rules out only the specific short being tested. It does not prove that every wire, sensor, connector, or circuit component is fault-free.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">7. Test Step 4: Check Whether CID 0269 FMI 03 Is Still Active<\/span><\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-25344\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-et-cid-0269-fmi-03-repair-verification.jpg\" alt=\"CAT ET diagnostic verification of MID 122 CID 0269 FMI 03 after checking the Caterpillar excavator sensor power and wiring harness\" width=\"960\" height=\"649\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-et-cid-0269-fmi-03-repair-verification.jpg 960w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-et-cid-0269-fmi-03-repair-verification-300x203.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-et-cid-0269-fmi-03-repair-verification-900x608.jpg 900w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-et-cid-0269-fmi-03-repair-verification-768x519.jpg 768w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/10\/cat-et-cid-0269-fmi-03-repair-verification-120x80.jpg 120w\" sizes=\"auto, (max-width: 960px) 100vw, 960px\" \/><\/p>\n<p><span data-preserver-spaces=\"true\">After completing the voltage and resistance checks, reconnect the system and verify the repair.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Test Procedure<\/span><\/h3>\n<ol>\n<li><span data-preserver-spaces=\"true\">Turn the key start switch to the OFF position.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Inspect the harness connectors for contamination, corrosion, or damaged terminals.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Clean the contacts with an appropriate electrical-contact cleaner when necessary.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Reconnect all harness connectors and make sure they are fully seated.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Turn the key start switch to the ON position.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Operate the machine under the conditions specified in the applicable Caterpillar service procedure.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Connect CAT ET and check whether MID 122 \u2013 CID 0269 \u2013 FMI 03 is still present and active.<\/span><\/li>\n<\/ol>\n<p><span data-preserver-spaces=\"true\">For additional guidance on retrieving fault codes, monitoring supported diagnostic information, and verifying repairs, see <\/span><a class=\"editor-rtfLink\" href=\"https:\/\/www.obd2tool.com\/blog\/how-to-use-cat-et-software\/\" target=\"_blank\" rel=\"noopener\"><span data-preserver-spaces=\"true\">How to Use CAT ET: Caterpillar Electronic Technician Diagnostic Guide<\/span><\/a><span data-preserver-spaces=\"true\">.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result A: The Diagnostic Code Remains Active<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">If CID 0269 FMI 03 remains active, the fault has not been corrected.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">Repeat the diagnostic procedure and verify:<\/span><\/p>\n<ul>\n<li><span data-preserver-spaces=\"true\">Sensor power supply voltage.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Product Link harness condition.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Machine sensor harness condition.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Connector terminal fit and electrical connections.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Connected sensor condition.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Other relevant circuits identified in the machine schematic.<\/span><\/li>\n<\/ul>\n<p><span data-preserver-spaces=\"true\">An ECM fault remains possible but is considered unlikely in the supplied procedure.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">If you cannot identify the cause after completing the required tests, contact a Caterpillar Technical Communicator before replacing the Product Link ECM. Follow the applicable Caterpillar ECM replacement procedure.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Result B: The Diagnostic Code Is No Longer Present<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">If CID 0269 FMI 03 is no longer present, the fault is not active at that time.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">A poor electrical connection or an intermittent short may have contributed to the original problem.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">Complete the required verification checks before returning the machine to normal operation.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">8. Troubleshooting Flowchart<\/span><\/h2>\n<p><span data-preserver-spaces=\"true\">Use this simplified sequence to organize the diagnostic process:<\/span><\/p>\n<ol>\n<li><strong><span data-preserver-spaces=\"true\">Check sensor power output:<\/span><\/strong><span data-preserver-spaces=\"true\"> Verify less than 4 VDC in the OFF state and less than 9 VDC in the ON state.<\/span><\/li>\n<li><strong><span data-preserver-spaces=\"true\">Check the Product Link harness:<\/span><\/strong><span data-preserver-spaces=\"true\"> If the voltage is outside the specified range, test for a short to battery.<\/span><\/li>\n<li><strong><span data-preserver-spaces=\"true\">Check the machine sensor harness:<\/span><\/strong><span data-preserver-spaces=\"true\"> Measure resistance between the specified sensor supply and battery power contacts.<\/span><\/li>\n<li><strong><span data-preserver-spaces=\"true\">Repair wiring faults:<\/span><\/strong><span data-preserver-spaces=\"true\"> Repair damaged wiring or replace the faulty harness as required.<\/span><\/li>\n<li><strong><span data-preserver-spaces=\"true\">Reconnect and verify:<\/span><\/strong><span data-preserver-spaces=\"true\"> Reconnect the harnesses and check the diagnostic code using CAT ET.<\/span><\/li>\n<li><strong><span data-preserver-spaces=\"true\">Escalate if unresolved:<\/span><\/strong><span data-preserver-spaces=\"true\"> If the code remains active, repeat the prescribed tests and contact Caterpillar technical support before considering ECM replacement.<\/span><\/li>\n<\/ol>\n<p><span data-preserver-spaces=\"true\">This systematic approach helps isolate the electrical fault and reduces unnecessary replacement of sensors or electronic control modules.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">9. Frequently Asked Questions<\/span><\/h2>\n<h3><span data-preserver-spaces=\"true\">What causes CID 0269 FMI 03 on a Caterpillar 311B excavator?<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The supplied diagnostic procedure associates the code with sensor power supply voltage above the normal range on circuit T930-WH-18. A short to battery voltage is the most likely cause. A faulty sensor or, less commonly, an ECM fault may also be involved.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">What is the nominal voltage of the T930-WH-18 sensor supply?<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The supplied diagnostic information states a nominal voltage of 8.3 VDC. The test procedure specifies less than 9 VDC in the ON state and less than 4 VDC in the OFF state.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Why must you check the Product Link harness?<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">A short between the sensor power circuit and battery power can raise the voltage above the normal range. The resistance test between J2-1 and J1-1 helps identify a short within the specified Product Link harness circuit.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">What resistance should be measured during the harness tests?<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">The specified resistance should be greater than 5,000 ohms between the contacts identified in each test step. Perform resistance measurements only with the relevant circuit de-energized and disconnected as instructed.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Can CAT ET help diagnose this fault?<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">CAT ET can help technicians retrieve supported diagnostic codes and verify whether CID 0269 FMI 03 remains active after repairs. Electrical measurements and harness inspections are still necessary to identify the underlying cause.<\/span><\/p>\n<h3><span data-preserver-spaces=\"true\">Should the ECM be replaced if the fault code returns?<\/span><\/h3>\n<p><span data-preserver-spaces=\"true\">Not immediately. The supplied procedure identifies ECM failure as unlikely. Complete the wiring, voltage, resistance, connector, and sensor checks first. Contact Caterpillar technical support before replacing the Product Link ECM if the fault remains unresolved.<\/span><\/p>\n<h2><span data-preserver-spaces=\"true\">Conclusion<\/span><\/h2>\n<p><span data-preserver-spaces=\"true\">The Caterpillar 311B excavator 2LS interference fault identified as MID 122 \u2013 CID 0269 \u2013 FMI 03 should be diagnosed by checking the sensor power supply circuit, Product Link harness, and machine sensor harness before considering ECM replacement.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">The key diagnostic points are:<\/span><\/p>\n<ul>\n<li><span data-preserver-spaces=\"true\">Verify the sensor power output is below 4 VDC in the OFF state and below 9 VDC in the ON state.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Check the specified harness contacts for resistance greater than 5,000 ohms.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Repair any short circuit or damaged wiring.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Reconnect the system and verify the diagnostic code using CAT ET.<\/span><\/li>\n<li><span data-preserver-spaces=\"true\">Consult Caterpillar technical support before replacing the Product Link ECM if the fault remains active and you cannot identify the cause.<\/span><\/li>\n<\/ul>\n<p><span data-preserver-spaces=\"true\">Following the prescribed test sequence helps isolate the electrical fault systematically and reduces unnecessary component replacement.<\/span><\/p>\n<p><span data-preserver-spaces=\"true\">For workshops diagnosing Caterpillar electronic systems, a compatible CAT ET setup and communication adapter can support fault-code retrieval and post-repair verification.<\/span><\/p>\n<ul>\n<li><a class=\"editor-rtfLink\" href=\"https:\/\/www.obd2tool.com\/goods-2485-CAT-Caterpillar-ET-Diagnostic-Adapter-III-PLUS-laptop.html\" target=\"_blank\" rel=\"noopener\"><span data-preserver-spaces=\"true\">CAT ET Diagnostic Adapter III with Laptop<\/span><\/a><\/li>\n<li><a class=\"editor-rtfLink\" href=\"https:\/\/www.obd2tool.com\/goods-10449-Cat-Caterpillar-ET-Electronic-Technician-Diagnostic-Software.html\" target=\"_blank\" rel=\"noopener\"><span data-preserver-spaces=\"true\">Caterpillar ET Electronic Technician Diagnostic Software<\/span><\/a><\/li>\n<\/ul>\n<p><em><span data-preserver-spaces=\"true\">Technical disclaimer: This article is based on the supplied diagnostic information. Confirm connector pin assignments, test conditions, and repair specifications against the correct Caterpillar service manual and electrical schematic for the machine&#8217;s serial number. Electrical testing and machine operation must follow applicable safety procedures.<\/span><\/em><\/p>\n<p><em><span data-preserver-spaces=\"true\">OBD2TOOL Technical Support Team \u2014 Caterpillar Diagnostic &amp; Repair Guides<\/span><\/em><\/p>\n<!-- AddThis Advanced Settings generic via filter on the_content --><!-- AddThis Share Buttons generic via filter on the_content -->","protected":false},"excerpt":{"rendered":"<p>The Caterpillar 311B excavator may log a 2LS interference fault (MID 122 \u2013 CID 0269 \u2013 FMI 03). According to<!-- AddThis Advanced Settings generic via filter on get_the_excerpt --><!-- AddThis Share Buttons generic via filter on get_the_excerpt --><\/p>\n","protected":false},"author":1,"featured_media":25340,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3224],"tags":[4609,4610,4614,4606,4611,4608,4607,4613,4612],"class_list":["post-25339","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-caterpillar-trouble-repair","tag-2ls-interference-fault","tag-cat-et-diagnostics","tag-cat-excavator-repair","tag-caterpillar-311b-excavator","tag-caterpillar-electrical-troubleshooting","tag-cid-0269-fmi-03","tag-mid-122","tag-product-link-ecm","tag-t930-wh-18"],"views":77,"_links":{"self":[{"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/posts\/25339","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/comments?post=25339"}],"version-history":[{"count":1,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/posts\/25339\/revisions"}],"predecessor-version":[{"id":25347,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/posts\/25339\/revisions\/25347"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/media\/25340"}],"wp:attachment":[{"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/media?parent=25339"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/categories?post=25339"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/tags?post=25339"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}