{"id":23720,"date":"2026-01-29T14:12:10","date_gmt":"2026-01-29T14:12:10","guid":{"rendered":"https:\/\/www.obd2tool.com\/blog\/?p=23720"},"modified":"2026-01-29T14:18:31","modified_gmt":"2026-01-29T14:18:31","slug":"caterpillar-c9-engine-throttle-position-out-of-calibration-28-pid-91-13-quick-fix-guide","status":"publish","type":"post","link":"https:\/\/www.obd2tool.com\/blog\/caterpillar-c9-engine-throttle-position-out-of-calibration-28-pid-91-13-quick-fix-guide\/","title":{"rendered":"Caterpillar C9 Engine Throttle Position Out of Calibration (28 \/ PID 91-13) \u2013 Quick Fix Guide"},"content":{"rendered":"<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23721\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-C9-throttle-calibration-troubleshooting-guide.jpg\" alt=\"\" width=\"856\" height=\"557\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-C9-throttle-calibration-troubleshooting-guide.jpg 856w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-C9-throttle-calibration-troubleshooting-guide-300x195.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-C9-throttle-calibration-troubleshooting-guide-768x500.jpg 768w\" sizes=\"(max-width: 856px) 100vw, 856px\" \/><\/p>\n<p>The fault code 28 \/ PID 91-13 \u2013 Throttle Position Out of Calibration is a common issue on Caterpillar C9 engines and is usually related to the accelerator pedal position sensor circuit or calibration.<\/p>\n<p>This short guide explains what the code means, why it occurs, and how to fix it efficiently.<\/p>\n<h2><strong>Related Contents:<\/strong><\/h2>\n<p><a href=\"https:\/\/www.obd2tool.com\/blog\/caterpillar-et-electronic-technician-software-free-download\/\">Caterpillar ET 2025C 2024A 2018A Diagnostic Software Free Download<\/a><\/p>\n<p><a href=\"https:\/\/www.obd2tool.com\/goods-333-Best+quality+CAT+Caterpillar+ET+Diagnostic+Tool.html\">CAT Communication Adapter 3 478-0235<\/a><\/p>\n<h2>What Triggers Code 28 \/ PID 91-13?<\/h2>\n<p>The Engine Control Module (ECM) will log this fault when all of the following conditions are met:<\/p>\n<ul>\n<li>The ECM 8-volt sensor supply drops below 7.5 VDC for more than 1 second<\/li>\n<li>The ECM has been powered for more than 3 seconds<\/li>\n<li>The accelerator pedal position signal is detected outside the calibrated range<\/li>\n<\/ul>\n<h2>Accelerator Pedal Position Sensor Overview<\/h2>\n<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23725\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-accelerator-pedal-position-sensor-for-C9-engine.jpg\" alt=\"\" width=\"493\" height=\"487\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-accelerator-pedal-position-sensor-for-C9-engine.jpg 493w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-accelerator-pedal-position-sensor-for-C9-engine-300x296.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-accelerator-pedal-position-sensor-for-C9-engine-120x120.jpg 120w\" sizes=\"(max-width: 493px) 100vw, 493px\" \/><\/p>\n<p>The accelerator pedal position sensor provides the throttle input signal to the ECM.<\/p>\n<ul>\n<li>Signal type: PWM (Pulse Width Modulated) \/ Duty Cycle<\/li>\n<li>Output range: 3% \u2013 100% duty cycle<\/li>\n<li>Low idle: 10% \u2013 22%<\/li>\n<li>Full throttle: 75% \u2013 90%<\/li>\n<li>ECM converts this signal to 3% \u2013 100% throttle position<\/li>\n<\/ul>\n<p>The sensor is mounted directly on the pedal assembly and does not require adjustment.<\/p>\n<p>\u26a0\ufe0f Important:<br \/>\nIf the pedal assembly is out of calibration, it cannot be adjusted.<br \/>\n\ud83d\udc49 The complete accelerator pedal assembly must be replaced.<\/p>\n<h2>Sensor Power Supply Information<\/h2>\n<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23726\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/aterpillar-ECM-connector-and-wiring-for-throttle-position-sensor.jpg\" alt=\"\" width=\"583\" height=\"538\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/aterpillar-ECM-connector-and-wiring-for-throttle-position-sensor.jpg 583w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/aterpillar-ECM-connector-and-wiring-for-throttle-position-sensor-300x277.jpg 300w\" sizes=\"(max-width: 583px) 100vw, 583px\" \/><\/p>\n<ul>\n<li>Sensor supply voltage: +8 VDC from the ECM<\/li>\n<li>Power source: ECM connector P1-4 \u2192 terminal \u201cA\u201d of the pedal sensor<\/li>\n<li>The sensor itself can be replaced separately, but calibration faults usually indicate a pedal assembly issue<\/li>\n<\/ul>\n<h2>PTO Configuration Note (Often Overlooked)<\/h2>\n<p>If the engine is operating in PTO mode, the accelerator pedal signal may be ignored when PTO is configured as:<\/p>\n<ul>\n<li>Remote switches<\/li>\n<li>Remote throttle<\/li>\n<\/ul>\n<h3>Cab Switches PTO Mode<\/h3>\n<ul>\n<li>The cab accelerator pedal can control engine RPM<\/li>\n<li>Or it can be ignored, depending on customer parameter settings<\/li>\n<li>Incorrect PTO programming can mimic a throttle calibration fault<\/li>\n<\/ul>\n<p>\ud83d\udc49 Always verify PTO configuration before replacing components.<\/p>\n<h2>Probable Causes (Check in This Order)<\/h2>\n<ol>\n<li>ECM electrical connections<\/li>\n<li>Accelerator pedal position sensor or harness<\/li>\n<li>Wiring between pedal sensor and ECM<\/li>\n<li>Accelerator pedal assembly (out of calibration)<\/li>\n<li>ECM failure (least common)<\/li>\n<\/ol>\n<h2>Recommended Diagnostic Steps<\/h2>\n<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23727\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-diagnostic-tool-showing-throttle-position-fault-code.jpg\" alt=\"\" width=\"492\" height=\"658\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-diagnostic-tool-showing-throttle-position-fault-code.jpg 492w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/Caterpillar-diagnostic-tool-showing-throttle-position-fault-code-224x300.jpg 224w\" sizes=\"(max-width: 492px) 100vw, 492px\" \/><\/p>\n<ol>\n<li>Verify ECM 8-volt sensor supply<\/li>\n<li>Inspect pedal connector and wiring<\/li>\n<li>Check live throttle duty-cycle data<\/li>\n<li>Confirm PTO parameter configuration<\/li>\n<li>Replace the accelerator pedal assembly if calibration is invalid<\/li>\n<\/ol>\n<p>Using a Caterpillar-compatible diagnostic tool is strongly recommended for accurate live data monitoring.<\/p>\n<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23728\" src=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/cat-et-software.jpg\" alt=\"\" width=\"1035\" height=\"624\" srcset=\"https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/cat-et-software.jpg 1035w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/cat-et-software-300x181.jpg 300w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/cat-et-software-900x543.jpg 900w, https:\/\/www.obd2tool.com\/blog\/wp-content\/uploads\/2026\/01\/cat-et-software-768x463.jpg 768w\" sizes=\"(max-width: 1035px) 100vw, 1035px\" \/><\/p>\n<h2>Summary<\/h2>\n<ul>\n<li>Code 28 \/ PID 91-13 is usually not an ECM failure<\/li>\n<li>Accelerator pedals cannot be recalibrated<\/li>\n<li>PTO configuration errors can cause false symptoms<\/li>\n<li>Proper diagnosis prevents unnecessary parts replacement<\/li>\n<\/ul>\n<p>More repair case for Caterpillar machine,please refer to:<a href=\"https:\/\/www.obd2tool.com\/blog\/category\/caterpillar-trouble-repair\/\">Caterpillar Machine Repair<\/a><\/p>\n<p>If you need help selecting a Caterpillar diagnostic tool to read live throttle data and ECM parameters, feel free to contact us <a href=\"https:\/\/www.obd2tool.com\">https:\/\/www.obd2tool.com<\/a><\/p>\n<p>&nbsp;<\/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 fault code 28 \/ PID 91-13 \u2013 Throttle Position Out of Calibration is a common issue on Caterpillar C9<!-- 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":23723,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3224],"tags":[3643],"views":353,"_links":{"self":[{"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/posts\/23720"}],"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=23720"}],"version-history":[{"count":3,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/posts\/23720\/revisions"}],"predecessor-version":[{"id":23729,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/posts\/23720\/revisions\/23729"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/media\/23723"}],"wp:attachment":[{"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/media?parent=23720"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/categories?post=23720"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.obd2tool.com\/blog\/wp-json\/wp\/v2\/tags?post=23720"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}