Circuit Description
The accelerator pedal position (APP) sensors 1 and 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 engine control module (ECM) with a signal voltage proportional to accelerator pedal movement. The APP sensors have opposite functionality. APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 1 volt at rest to above 2.5 volts when fully depressed. The APP sensor 2 signal voltage decreases as the pedal is depressed, from 4 volts at rest to less than 1 volt with the accelerator pedal fully depressed. If the ECM detects that the APP sensor 1 signal voltage is not within the predicted range, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2120 Accelerator Pedal Position (APP) Sensor 1 Circuit
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The ignition voltage is greater than 5.23 volts. |
| • | DTCs P0601, P0602, P0603, P0604, P0606, P0607, P0641, P0651 are not set. |
| • | DTC P2120 runs continuously when the above conditions are met. |
Conditions for Setting the DTC
The APP sensor 1 voltage is less than 0.36 volt or more than 2.6 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: 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 | |
2 |
Does the scan tool indicate voltage less than the first value or greater than the second value? | 0.36 V 2.6 V | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 |
Does the scan tool indicate voltage at the specified value? | 0 V | Go to Step 5 | Go to Step 10 |
5 |
Does the scan tool indicate the APP sensor 1 voltage at the specified value? | 5 V | Go to Step 6 | Go to Step 7 |
6 | Probe the APP sensor low reference circuit with a test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 12 |
7 | Measure the voltage of the APP sensor 1 5-volt reference circuit with a DMM. Does the DMM indicate voltage at the specified value? | 5 V | Go to Step 9 | Go to Step 8 |
8 | Does the DMM indicate voltage less than the specified value on the APP sensor 1 5-volt reference circuit? | 5 V | Go to Step 13 | Go to Step 15 |
9 | Test the APP sensor 1 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 20 | Go to Step 11 |
10 | Test the APP sensor 1 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 |
11 | Test the APP sensor 1 signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 |
12 | Test the APP sensor 1 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 20 | Go to Step 18 |
13 | Test the APP sensor 1 5-volt 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 20 | Go to Step 14 |
14 | Test the APP sensor 1 5-volt reference circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 |
15 | Test the APP sensor 1 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 20 | -- |
16 | Inspect for poor connections 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 20 | Go to Step 17 |
17 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- |
18 | Inspect for poor connections at the engine control module (ECM) harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 |
19 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 20 | -- |
20 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 21 |
21 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
