For 1990-2009 cars

### Circuit Description

The accelerator pedal position (APP) sensor 1 and sensor 2 are located within the accelerator pedal assembly. Each sensor has the following circuits:

• | A 5-volt reference circuit

• | A low reference circuit

• | A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated. If the PCM detects that the APP sensor 2 signal voltage is not within the predicted range, DTC P2128 sets.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

### Conditions for Running the DTC

• | The ignition switch is in the Unlock, Accessory, Run, or Crank position.

• | The ignition voltage is more than 5.23 volts.

• | DTC P0641 is not set.

• | DTC P2128 runs continuously when the above conditions are met.

### Conditions for Setting the DTC

The PCM detects that the APP sensor 2 voltage is more than 4.65 volts for more than 0.4 second.

### Action Taken When the DTC Sets

• | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.

• | The control module commands the TAC system to operate in the Reduced Engine Power mode.

• | A message center or an indicator displays Reduced Engine Power.

• | Under certain conditions the control module commands the engine OFF.

### Conditions for Clearing the MIL/DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Clear the MIL and the DTC with a scan tool.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn ON the ignition, with the engine OFF.
2. Observe the accelerator pedal position (APP) sensor 2 voltage with the accelerator pedal in the rest position, with a scan tool.

Is the APP sensor 2 voltage parameter more than the specified value?

4.65 V

Go to Step 4

Go to Step 3

3 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the Conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Testing for Intermittent Conditions and Poor Connections

4 |

1. Turn OFF the ignition.
2. Disconnect the accelerator pedal connector.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage of the APP sensor 2 5-volt reference circuit to a good ground, with a DMM.

Does the DMM indicate voltage within the specified range?

4.8-5.2 V

Go to Step 5

Go to Step 10

5 | With a test lamp connected to ground, probe the APP sensor 2 signal circuit. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 6
6 | Observe the APP Sensor 2 parameter, with the test lamp still connected to the APP sensor 2 signal circuit. Does the scan tool indicate voltage at the specified value? | 0 V | Go to Step 9 | Go to Step 7
7 | Test the APP sensor 2 signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13
8 | Test the APP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 11
9 | Test the APP sensor 2 low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13
10 | Test the APP sensor 2 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 11
11 | Test for shorted terminals and for a poor connection at the powertrain control module (PCM) harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | - | Go to Step 16 | Go to Step 15
12 | Test for an intermittent and for a poor connection at the accelerator pedal harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14
13 | Test for an intermittent and for a poor connection at the PCM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? |  | Go to Step 16 | Go to Step 15
14 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | --
15 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 16 | --
16 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 17

17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK