CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 132

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Overview

ISX and ISM – Accelerator Pedal Position Sensor Circuit SMALL | MEDIUM | LARGE

Circuit Description

The accelerator position sensor is a potentiometer attached to the accelerator pedal. The accelerator position sensor varies the signal voltage to the electronic control module (ECM) as the accelerator pedal is depressed and released. Low signal voltage is received by the ECM when the accelerator pedal is at 0 percent. A high signal voltage is received by the ECM when the accelerator pedal is at 100 percent. The accelerator pedal position circuit contains an accelerator pedal position 5 volt supply, accelerator pedal position return, and accelerator pedal position signal.

When the ECM senses a signal voltage lower than the normal operating range of the sensor, this fault code is set.

Note: The sensor connection pin numbers shown is the diagram above are OEM specific and those provided are for example only. Refer to the OEM diagram for correct pinouts.

Component Location

The accelerator pedal or lever position sensor is mounted to the accelerator pedal assembly. Refer to the original equipment manufacturer (OEM) troubleshooting and repair manual.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes

The ECM detects that the throttle pedal signal voltage is less than 0.75-VDC for more than 1 second.

Action Taken When the Fault Code is Active

• The ECM illuminates the red STOP ENGINE light immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code

The ECM will turn off the red STOP ENGINE light immediately after the diagnostic runs and passes.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

Newer engines use two throttle position sensors to determine the throttle position. Older throttle pedals used a single throttle position sensor and an idle validation switch. If Fault Codes 132 and 1241 are active when the accelerator pedal is in the idle position, and Fault Code 132 goes inactive, and Fault Code 1239 goes active when the throttle is depressed, the incorrect throttle pedal has been installed in the vehicle. A throttle pedal with two acceleration position sensors must be installed.

If troubleshooting an intermittent accelerator problem:

The accelerator pedal or lever position sensor signal voltage can be monitored with the INSITE™ electronic service tool, while flexing the harness to locate the intermittent connection. Intermittent connections will show up as abrupt changes in signal voltage displayed by INSITE™ electronic service tool.

Possible causes of this fault include:

• Accelerator pedal or lever position signal shorted to engine ground or return wires in the OEM harness or sensor
• Failed accelerator pedal or lever position sensor
• Open circuit in the accelerator signal, supply, or return wire in the harness or connectors.

Note: The three wires in the accelerator position sensor circuit must be twisted together.

Refer to Troubleshooting Fault Code t05-132