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Electronic Control System Gas Plus Engines – FAULT CODE 387

Accelerator Pedal or Lever Position Sensor Supply Voltage Circuit – Shorted High

Overview

CODE REASON EFFECT
Fault Code: 387
PID: S221
SPN: 1043
FMI: 3
LAMP: Amber
SRT: 

Accelerator Pedal or Lever Position Sensor Supply Voltage Circuit – Voltage Above Normal, or shorted to high source. High voltage detected at sensor supply circuit for the accelerator pedal position sensor.

Engine idles when the idle validation switch indicates idle and ramps up to a default set speed when the idle validation switch indicates off idle.

Accelerator Pedal or Lever Position Sensor Supply Voltage Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The accelerator pedal position sensor sends a signal to the electronic control module (ECM) to indicate to the ECM the rate at which the driver wants to accelerate the vehicle.

Component Location

The accelerator pedal position sensor is located on the accelerator pedal.

Shop Talk

  • Make sure there are no external circuits hooked into the accelerator pedal position sensor circuit and that there are no signs of tampering in the circuit.
  • If all the wiring and sensor checks are okay, replace the accelerator pedal position sensor and the idle validation switch circuit wires, between the accelerator pedal and ECM, with new wires. Run the wires through or around the bulkhead without using the bulkhead connector. Test the vehicle with the test wires in place. If the fault code goes away, replace the OEM harness.
  • Verify that the accelerator pedal position sensor wires are twisted together.

Cautions and Warnings

 CAUTION 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated prior to replacing the ECM.
 CAUTION 

To reduce the possibility of pin and harness damage, use the following test leads when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead
Part Number 3823993 – male Deutsch test lead.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Check for an inactive fault code. Fault Code 387 inactive?
STEP 2. Check the ECM and engine harness.  
  STEP 2A. Inspect the ECM and engine harness connector pins. Dirty or damaged pins?
  STEP 2B. Check for a pin to pin short circuit in the engine harness. Greater than 100k ohms?
  STEP 2C. Check for an inactive fault code. Fault Code 387 inactive?
STEP 3. Clear the fault codes.  
  STEP 3A. Disable the fault code. Fault Codes 387 inactive?
  STEP 3B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check the fault codes.

Guided Step 1A – Check for an inactive fault code.

Conditions

  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 387 inactive?
YES NO
No Repair No Repair

Guided Step 2 – Check the ECM and engine harness.

Guided Step 2A – Inspect the ECM and engine harness connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness connector 2 from the ECM.

Action

  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Wire insulation damaged
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Connector shell broken
  • Dirt or debris in or on the connector pins.

For general inspection techniques, refer to Component Connector and Pin Inspection, Procedure 019-361.

Dirty or damaged pins?
YES NO

A defective connection has been detected in the ECM engine connector or engine harness connector.

Repair the damaged pins.

Repair or replace the engine harness, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Install the appropriate connector seal if it is damaged or missing.
  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.
No Repair

Guided Step 2B – Check for a pin to pin short circuit in the engine harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness connector 2 from the ECM.
  • Disconnect the accelerator pedal from the OEM harness
  • Make sure all components connected to the accelerator pedal supply are disconnected.

Action

  • Measure the resistance from the accelerator pedal SUPPLY pin in engine harness ECM connector 2 to all other pins in the ECM connector 2.
  • Measure the resistance from the accelerator pedal SUPPLY pin in engine harness ECM connector 2 to all pins in the ECM connector 1.
SMALL | MEDIUM | LARGE

Greater than 100k ohms?
YES NO

A pin to pin short circuit on the accelerator pedal supply line has been detected in the engine harness.

Repair the damaged pins.

Repair or replace the engine harness or OEM harness, whichever has the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Install the appropriate connector seal if it is damaged or missing.
  • Repair the engine harness. Refer to Procedure 019-204.
  • Replace the engine harness. Refer to Procedure 019-043.
  • Refer to the OEM Troubleshooting and Repair Manual.
 No Repair

Guided Step 2C – Check for an inactive fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 387 inactive?
YES NO
No Repair

Replace the ECM. Call for pre-authorization.

Refer to Procedure 019-031.

Guided Step 3 – Clear the fault codes.

Guided Step 3A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Start the engine and let it idle for one minute.
  • Use INSITE™ electronic service tool to verify that the fault code is inactive.

Fault Codes 387 inactive?
YES NO
No Repair No Repair

Guided Step 4B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to erase the inactive fault codes.

All fault codes cleared?
YES NO
No Repair No Repair
Repair complete
Appropriate troubleshooting charts
Last Modified:  03-Sep-2004
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