| Table 1: | APP Sensor Position Table |
Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is made up of 3 individual sensors within one housing.
The accelerator pedal position sensor 1, sensor 2, and sensor 3 are potentiometer type sensors, each with the following circuits:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A signal circuit |
The engine control module (ECM) provides the APP sensors a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the ECM signal voltages proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is high at rest and decreases as the pedal is depressed. The APP sensor 3 signal voltage is high at rest and decreases as the pedal is depressed.
When the ECM detects that the APP sensor 1 signal and the APP sensor 2 signal circuits are out of the correlation, DTC will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1271 Accelerator Pedal Position (APP) Sensor 1-2 Correlation
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The APP sensor 1 and APP sensor 2 are more than 10 percent out of range of each other.
Action Taken When the DTC Sets
| • | The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records. |
| • | If all 3 APP sensors are out of range, the APP indicated angle is limited to 0 percent. The ECM only allows the engine to idle. |
Conditions for Clearing the DTC
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | Clear the MIL and the DTC with a scan tool. |
APP Sensor | Actual Pedal Position | % Depressed as Observed on a Scan Tool | Voltage as Observed on a Scan Tool |
|---|---|---|---|
1 | Pedal at rest | 0 | 0.52-0.80 |
1 | Pedal at full travel | 100 | 2.38-2.66 |
2 | Pedal at rest | 0 | 4.20-4.48 |
2 | Pedal at full travel | 100 | 2.34-2.62 |
3 | Pedal at rest | 0 | 3.92-4.09 |
3 | Pedal at full travel | 100 | 2.79-2.96 |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 | Is DTC P0641, P0651, P1646, P1287 or P1288 also set? | -- | Go to Step 5 | |
5 | Is DTC P1272 also set? | -- | Go to Step 7 | Go to Step 6 |
6 | Is DTC P1273 also set? | -- | Go to Step 10 | -- |
7 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 14 |
8 | With a test lamp connected to ground, test for voltage at the APP sensor 2 signal circuit. Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 15 |
9 | Connect a test lamp between the APP sensor 2, 5-volt reference circuit and the APP sensor 2 low reference circuit. Does the test lamp illuminate? | -- | Go to Step 19 | Go to Step 16 |
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 17 |
11 | Connect the test lamp between the APP sensor 1, 5-volt reference circuit and the APP sensor 1 low reference circuit. Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 18 |
12 |
Does the scan tool indicate voltage at the specified value? | 5 V | Go to Step 19 | Go to Step 13 |
13 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
14 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
15 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
16 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
17 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
18 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
19 | Inspect for poor connections at the harness connector of the APP sensor. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 20 |
20 | Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 23 | -- |
21 | Inspect for poor connections at the harness connector of the ECM. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 22 |
22 |
Important: The replacement ECM must be programmed. Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming . Did you complete the replacement? | -- | Go to Step 23 | -- |
23 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 24 |
24 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
