Circuit Description
The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the sensors. The 5-volt reference for the APP sensor 2 is supplied from the same source in the ECM as the 5-volt reference for the throttle position sensors. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to a voltage supply. The APP sensor 2 sends a signal indicating the accelerator pedal position and the ECM actuates the throttle plates based on this information. The APP sensor 2 signal voltage increases from about 0.2 volts at rest to about 1.8 volts when fully depressed. If the ECM detects that the signal voltage is excessively high, DTC P2128 sets.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The battery voltage is more than 10 volts. |
| • | The accelerator pedal is not in the rest position. |
Conditions for Setting the DTC
The APP sensor 2 voltage is more than 4.6 volts for more than 140 milliseconds.
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 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: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Is the APP sensor 2 voltage more than the specified value? | 4.6 V | Go to Step 3 | Go to Step 4 |
3 |
Is the APP sensor 2 voltage less than the specified value? | 0.02 V | Go to Step 6 | Go to Step 13 |
4 |
Does the DTC fail this ignition? | -- | Go to Step 6 | Go to Step 5 |
5 |
Did the DTC fail this ignition? | -- | Go to Step 19 | Go to Intermittent Conditions |
6 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 7 | Go to Step 11 |
7 |
Is the APP sensor 2 voltage within the specified value? | 4.8-5.2 V | Go to Step 8 | Go to Step 13 |
8 |
Important: It may be necessary to remove the ECM/TCM fuse to allow the ECM to power down. Is the resistance less than the specified value? | 5 ohms | Go to Step 16 | Go to Step 9 |
9 | Test the low reference circuit of the APP sensor 2 for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 10 |
10 | Measure the resistance from the case of the ECM to the battery ground. Is the resistance less than the specified value? | 5 ohms | Go to Step 17 | Go to Step 15 |
11 |
Is the voltage within the specified range after disconnecting any component? | 4.8-5.2 V | Go to Step 18 | Go to Step 12 |
12 | Test the 5-volt reference circuit of the APP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 14 |
13 | Test the signal circuit of the APP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 17 |
14 | Test the 5-volt reference circuits of the throttle position (TP) sensors for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 17 |
15 | Repair the open or high resistance in the ECM ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- |
16 | Test for an intermittent and for a poor connection at the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 19 |
17 | Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20 |
18 | Replace the component that when disconnected, caused the voltage to return to the specified value. Refer to the appropriate replacement procedure. Did you complete the replacement? | -- | Go to Step 21 | -- |
19 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- |
20 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- |
21 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 22 |
22 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
