For 1990-2009 cars

### Circuit Description

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

The APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 1.0 volt at rest to above 4 volts when fully depressed. The APP sensor 2 signal voltage increases as the pedal is depressed, from approximately 0.5 volt at rest to more than 2 volts with the accelerator pedal fully depressed.

If the ECM detects that the APP sensor 2 signal voltage is too high, this DTC 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 is ON or the engine is running.

• | The ignition 1 voltage is more than 7 volts.

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

### Conditions for Setting the DTC

The APP sensor 2 voltage is more than 4.82 volts for more than 4 seconds.

### 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/Failure Records.

### Conditions for Clearing the MIL/DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 4 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.

### Diagnostic Aids

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views .

• | If DTCs P0700, P2122, P2128, and P2138 are set together in various combinations, inspect the APP sensor 1 and 2 signal circuits for being shorted together.

• | For an intermittent condition, refer to Intermittent Conditions .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step tests the internal circuits of the APP sensor 2 throughout its range of motion. If this DTC sets when slowly moving the pedal from the rest position to wide open throttle (WOT), replace the APP assembly for an internal fault.

2. This step tests for high resistance in the low reference circuit of the APP sensor 2. The ECM must be completely powered OFF to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to power OFF completely.

#### P2128

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine 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 the ignition switch to ON position, with the engine OFF.
2. Observe the APP sensor 2 voltage, with a scan tool.
3. Depress the accelerator pedal to wide open throttle (WOT).

Is the voltage more than the specified value?

2.40 V

Go to Step 5

Go to Step 3

3 |

1. Observe the DTC information with a scan tool.
2. Slowly depress the accelerator pedal to WOT, then slowly return the accelerator pedal to the closed position.
3. Repeat this action several times.

Did the DTC fail this ignition?

--

Go to Step 13

Go to Step 4

4 |

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 5

Go to Diagnostic Aids

5 |

1. Turn OFF the ignition.
2. Disconnect the APP sensor harness connector. Refer to Accelerator Pedal Position Sensor Replacement .
3. Turn the ignition switch to ON position, with the engine OFF.
4. Observe the APP sensor 2 voltage with the scan tool.

Is the voltage less than the specified value?

0.1 V

Go to Step 6

Go to Step 10

6 | Measure the voltage from the 5-volt reference circuit of the APP sensor 2 to a good ground, with a DMM. Is the voltage more than the specified value? | 6 V | Go to Step 9 | Go to Step 7
7 |

1. Turn OFF the ignition.
2. Remove the ECM/TCM fuse from the underhood fuse block.

Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.

3. Measure the resistance from the low reference circuit of the APP sensor 2 to good ground, with a DMM.

Is the resistance less than the specified value?

10 Ω

Go to Step 11

Go to Step 8

8 |

1. Turn OFF the ignition.
2. Disconnect the ECM.

Important: A short to voltage on the low reference circuit may cause internal ECM damage and sensor damage.

3. Test the low reference circuit of the APP sensor 2 for an open, for a short to voltage, or for a high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

9 | Important: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.

Test the 5-volt reference circuit of the APP sensor 2 for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

10 | Test the signal circuit of the APP sensor 2 for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12
11 | Test for shorted terminals and poor connections at the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13
12 | Test for shorted terminals and poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
13 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | --
14 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 15 | --
15 |

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 16

16 | 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