CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 2186

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Overview

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

Circuit Description

Sensor supply 4 of the electronic control module (ECM) provides a 5 volt supply to the accelerator pedal position sensor. The accelerator position sensor is a potentiometer attached to the accelerator pedal. The accelerator position sensor varies the signal voltage to the 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 position 5 volt supply, accelerator pedal position return, and accelerator pedal position signal.

Component Location

The accelerator pedal is located in the cab. 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 sensor supply 4 signal voltage is less than 4.75 VDC for more than 1 second.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• The engine will only die.

Conditions for Clearing the Fault Code

The ECM will turn off the amber CHECK 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.

Low voltage on the +5 volt supply line can be caused by a short circuit to ground in the supply line, a short circuit between the supply line and return circuit, a malfunctioning accelerator, or a malfunctioning ECM power supply.

Refer to Troubleshooting Fault Code t05-2186