For 1990-2009 cars

### 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 P2120 00: Accelerator Pedal Position (APP) Sensor 1 Circuit
DTC P2122 00: Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage
DTC P2123 00: Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage
DTC P2125 00: Accelerator Pedal Position (APP) Sensor 2 Circuit
DTC P2127 00: Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage
DTC P2128 00: Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage
DTC P2138 00: Accelerator Pedal Position (APP) Sensors 1-2 Not Plausible

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference Circuit | P06A3 00, P2122 00 | P2122 00, P2128 00 | P06A3 00, P2135 00 | P2138 00
Accelerator Pedal Position (APP) Sensor 1 Signal | P2122 00 | P2122 00, P2138 00 | P06A3 00, P2123 00 | P2138 00
Accelerator Pedal Position (APP) Sensor 1 Low Reference | -- | P2123 00, P2138 00 | -- | P2138 00
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference Circuit | P0107 00, P0697 00 | P2127 00, P2138 00 | P0106 00, P0108 00, P0697 00 | P2138 00
Accelerator Pedal Position (APP) Sensor 1 Signal | P2122 00 | P2122 00, P2138 00 | P06A3 00, P2123 00 | P2138 00
Accelerator Pedal Position (APP) Sensor 2 Low Reference | -- | P2128 00, P2138 00 | -- | P2138 00

### Typical Scan Tool Data

#### APP Sensor 1 and 2

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating at idle Parameter Normal Range: APP Sensor 1 0.88-1.08 V Parameter Normal Range: APP Sensor 2 0.39-0.59 V
APP Sensor 1 5-V Reference | 0.00 V | 0.00 V | 2.75 V
APP Sensor 1 Signal | 0.00 V | 0.00 V | 4.98 V
APP Sensor 1 Low Reference | -- | 4.96 V | --
APP Sensor 2 5-V Reference | 0.00 V | 0.00 V | 1.35 V
APP Sensor 2 Signal | 0.00 V | 0.00 V | 4.98 V
APP Sensor 2 Low Reference | -- | 4.92 V | --

### Circuit/System Description

The accelerator pedal assembly contains 2 accelerator pedal position (APP) sensors. The APP sensors are mounted to the accelerator pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to pedal position. The engine control module (ECM) supplies each APP sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit.

Both the APP sensors 1 and 2 signal percentages increase as the pedal is depressed, from approximately 0% at rest to above 95% when fully depressed.

### Conditions for Running the DTC

#### P2120 00, P2122 00, P2123 00, P2125 00, P2127 00, P2128 00

• | DTC P06A3 00 or P0697 00 are not set.

• | The ignition is ON or the engine is operating.

• | The ignition voltage is greater than 6 V.

• | The ECM is not commanding reduced power.

• | The DTCs run continuously when the above conditions are met.

#### P2138 00

• | DTCs P06A3 00, P0697 00, P2122 00, P2123 00, P2125 00, P2127 00, or P2128 00 are not set.

• | The ignition is ON or the engine is operating.

• | The ignition voltage is greater than 6 V.

• | The ECM is not commanding reduced power.

• | The DTC runs continuously when the above conditions are met.

### Conditions for Setting the DTC

#### P2120 00

The ECM detects that APP sensor 1 voltage is less than 0.59 V for greater than 0.4 s.

#### P2122 00

The ECM detects that the APP sensor 1 voltage is less than 0.46 V for less than 1 s.

#### P2123 00

The ECM detects that the APP sensor 1 voltage is greater than 4.7 V for less than 1 s.

#### P2125 00

The ECM detects that the APP Sensor 2 voltage is less than 0.5 V for less than 1 s.

or

The ECM detects that the APP Sensor 2 voltage is greater than 4.8 V for less than 1 s.

#### P2127 00

The ECM detects that the APP sensor 2 voltage is less than 0.32 V for less than 1 s.

#### P2128 00

The ECM detects that APP sensor 2 voltage is greater than 2.64 V for greater than 0.5 s.

#### P2138 00

The ECM detects that APP sensor 1 and APP sensor 2 disagree greater than 10% for less than 1 s.

or

The ECM detects that both APP sensor 1 and APP sensor 2 are 5% greater than the learned minimum position for less than 1 s.

### Action Taken When the DTC Sets

• | DTCs P2120 00, P2122 00, P2123 00, P2125 00, P2127, 00 and P2128 00, and P2138 00 are Type C DTCs.

• | DTC P2138 is a Type B DTC.

• | The ECM commands the throttle body (TAC) motor system to operate in reduced engine power mode.

### Conditions for Clearing the DTC

• | DTCs P2120 00, P2122 00, P2123 00, P2125 00, P2127, 00 and P2128 00, and P2138 00 are Type C DTCs.

• | DTC P2138 is a Type B DTC.

### Diagnostic Aids

• | If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

• | The scan tool 5-volt reference parameter should display between 4.8-5.2 V.

• | A high resistance condition on the accelerator pedal position (APP) sensor circuits may cause a DTC to set.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Throttle Actuator Control (TAC) System Description

#### 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

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0697 00 or P06A3 00 are not set.

⇒ | If a DTC is set, refer to DTC P0641, P0651, P0697, or P06A3.

2. Ignition ON, observe the scan tool APP Sensor 1 and 2 Indicated parameters. Both parameters should be 0%.
3. Observe the scan tool APP Sensor 1 and 2 Agree/Disagree parameter while performing the following tests:

• | Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times.

• | Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.

⇒ | The APP sensor 1 and 2 Agree/Disagree parameter should display Agree.

4. Observe the DTC information with a scan tool. DTCs P2120 00, P2122 00, P2123 00, P2127 00, P2128 00, or P2138 00 should not set.
5. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame / failure records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the B107 Accelerator Pedal Position Sensor harness connector at the accelerator pedal assembly.
2. Ignition OFF for 1 min, test for less than 5 Ω between the low reference circuit terminals listed below and ground.

• | Low reference circuit terminal 4

• | Low reference circuit terminal 5

⇒ | If greater than the specified range, test the appropriate low reference circuit for a short to voltage, or an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

3. Ignition ON, test for 4.8-5.2 V between both 5-volt reference circuit terminals listed below and ground.

• | 5 V reference circuit terminal 1

• | 5 V reference circuit terminal 2

⇒ | If less than the specified range, test the appropriate 5-volt reference circuit for a short to ground or open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

4. Verify the appropriate APP sensor voltage parameter is at 0 V.

⇒ | If greater than the specified range, test the appropriate signal circuit terminal listed below for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

• | APP sensor 1 signal circuit terminal 3

• | APP sensor 2 signal circuit terminal 6

5. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and the 5-volt reference circuit terminal 1 of the appropriate B107 Accelerator Pedal Position Sensor. Verify the appropriate APP Sensor voltage parameter is greater than 4.8 V.

• | APP sensor 1 signal circuit terminal 3

• | APP sensor 2 signal circuit terminal 1

⇒ | If less than the specified range, test the appropriate signal circuit for a short to ground or an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

6. If all circuits test normal, replace the accelerator pedal assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | LINK 176280

• | Control Module References for ECM replacement, setup, and programming