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 |
The APP sensor provides the engine control module (ECM) 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 also near the low reference and increases as the pedal is actuated. When the ECM detects that the APP sensor 1 signal voltage is outside the predicted range, DTC P1275 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 more than 5.25 volts. |
| • | DTC P0651 is 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 0.13 volts or more than 4.87 volts for more than 0.5 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 Controls Connector End Views or Engine Control Module 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? | 0.13 V 4.87 V | Go to Step 5 | Go to Step 3 |
3 | Is DTC P2138 also set? | -- | Go to Step 4 | |
4 |
Does the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions |
5 |
Does the scan tool indicate that the voltage is less than the specified value? | 0.13 V | Go to Step 6 | Go to Step 11 |
6 |
Does the scan tool indicate that the APP sensor 1 voltage is more than the specified value? | 4.8 V | Go to Step 7 | Go to Step 8 |
7 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 17 | Go to Step 13 |
8 | Measure the voltage of the APP sensor 1 5-volt reference circuit with a DMM. Does the DMM indicate that the voltage is more than the specified value? | 4.8 V | Go to Step 10 | Go to Step 9 |
9 | Does the DMM indicate that the voltage is less than the specified value on the APP sensor 1 5-volt reference circuit? | 5 V | Go to Step 14 | Go to Step 16 |
10 | Test the APP sensor 1 signal circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 12 |
11 | 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 21 | Go to Step 19 |
12 | 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 21 | Go to Step 19 |
13 | Test the APP sensor 1 low reference circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 19 |
14 | 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 21 | Go to Step 15 |
15 | 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 21 | Go to Step 19 |
16 | 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 21 | -- |
17 | 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 21 | Go to Step 18 |
18 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal with Position Sensor Assembly Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- |
19 | Inspect for poor connections at the 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 21 | Go to Step 20 |
20 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. 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 |
Important: Be aware that repairing one individual condition may correct more than one DTC. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
