GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P1125: Accelerator Pedal Position (APP) System

Diagnostic Fault Information

Circuit

Short to Ground

Open

Short to Voltage

APP 1 Sensor 5-Volt Reference

P0642

P2122

--

APP 1 Sensor Signal

P2122

P2122

P2123

APP 1 Sensor GND

--

P2123

--

APP 2 Sensor 5-Volt Reference

P0652

P2127

--

APP 2 Sensor Signal

P2127

P2128

P2128

APP 2 Sensor GND

--

P2128

--

APP 3 Sensor 5-Volt Reference

P0698

P2132

--

APP 3 Sensor Signal

P2132

P2133

P2133

APP 3 Sensor GND

--

P2133

--

Typical Scan Tool Data

APP Sensor

APP Sensor

Actual Pedal Position

(%) Depressed as Observed on a Scan Tool

Voltage as Observed on a Scan Tool

Operating Conditions: Ignition ON

Parameter Normal Range: 0-100

APP 1

Pedal at reset

0

0.52-0.80

APP 1

Pedal at full travel

100

2.12-2.78

APP 2

Pedal at reset

0

4.25-4.53

APP 2

Pedal at full travel

100

2.24-2.93

APP 3

Pedal at reset

0

3.95-4.13

APP 3

Pedal at full travel

100

2.69-3.16

Circuit/System Description

The accelerator pedal position (APP) sensor is mounted on the accelerator pedal control assembly. The sensor is made up of three individual sensors within one housing. The APP sensor 1, APP sensor 2, and APP sensor 3 are potentiometer type sensors. The engine control module (ECM) supplies 5 volts to the APP sensor on the 5-volt reference circuits. The ECM also provides a ground on the low reference circuits. The APP sensor provides a signal to the ECM on the APP sensor signal circuits, which is relative to the position changes of the accelerator pedal angle. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is high at rest and decreases as the pedal is depressed. The APP sensor 3 signal is high at rest and decreases as the pedal is depressed.

Conditions for Running the DTC

DTCs P0642, P0643, P0652, P0653, P0698 and P0699 are not set.

Conditions for Setting the DTC

One or more of the APP sensor signals contain an open or short circuit.

Action Taken When the DTC Sets

DTC P1125 is a Type B DTC.

Conditions for Clearing the DTC

DTC P1125 is a Type B DTC.

Diagnostic Aids

Inspect for any recent engine mechanical repairs. An incorrectly installed APP sensor will cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Component Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Important:  If DTCs P0642, P0643, P0652, P0653, P0698 and P0699 are set, test and repair those DTCs first.

Verify the integrity of the accelerator pedal, accelerator pedal position (APP) sensor by inspecting for the following conditions:

    • Damaged components
    • Loose or improper installation

Circuit/System Testing

Important: You must perform Circuit/System Verification before proceeding with Circuit/System Testing.

  1. With the ignition ON, test for 4.8-5.2 volts between the applicable APP sensor 5-volt reference circuit and ground.
  2. If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.
    If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the control module.
  3. Using a DMM, measure the voltage between the 5-volt reference circuit and a low reference circuit.
  4. If less than 4.8 volts, test the low reference circuit for an open circuit.
  5. Install a 3-amp fused jumper wire between the applicable signal circuit and the applicable 5-volt reference circuit for APP sensor 2 and 3. Verify that the scan tool accelerator position (APP) sensor parameter is greater than 5 volts.
  6. If less than 4.8 volts, test the applicable signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.
    If more than 5.2 volts, replace the accelerator pedal assembly.
  7. Install a 3-amp fused jumper wire between the applicable signal circuit and the applicable 5-volt reference circuit for APP sensor 1. Verify that the DMM volt meter scan tool accelerator position (APP) sensor parameter is greater than 5 volts.
  8. If less than 4.8 volts, test the applicable signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.
    If more than 5.2 volts, replace the accelerator pedal assembly.

Component Testing

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Accelerator Pedal Position Sensor Replacement
    •  Control Module References for engine control module (ECM) replacement, setup, and programming