| Table 1: | APP Sensor Position Table |
| Table 2: | DTC P1271 APP sensor 1-2 correlation |
Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal control assembly. The sensor is made up of 3 individual sensors within 1 housing. Three separate signal, low reference, and 5-volt reference circuits are used in order to interface the APP sensor with the engine control module (ECM). Each sensor has a unique functionality to determine pedal position as shown in the table below. The ECM uses the APP sensor to determine the amount of acceleration or deceleration desired by the person driving the vehicle via fuel injector control. This DTC sets if the ECM determines an out of range condition with the APP sensor.
APP Sensor | Actual Pedal Position | % Depressed as Observed on a Scan Tool | Voltage as Observed on a Scan Tool |
|---|---|---|---|
1 | Pedal at rest | 0 | .52 - .80 |
1 | Pedal at full travel | 100 | 2.12 - 2.78 |
2 | Pedal at rest | 0 | 4.25 - 4.53 |
2 | Pedal at full travel | 100 | 2.24 - 2.93 |
3 | Pedal at rest | 0 | 3.95 - 4.13 |
3 | Pedal at full travel | 100 | 2.69 - 3.16 |
Conditions for Running the DTC
| • | DTCs P1277, P1278, P1287, P1288, P1635, or P1639 are not set. |
| • | The ignition switch is in the crank or run position. |
| • | The ignition voltage is between 7-16 volts. |
Conditions for Setting the DTC
| • | The APP sensor 1 and APP sensor 2 are more than 10 percent out of range of each other. |
| • | All of the above conditions present for less than 1 second. |
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | If one or more APP sensor DTCs are set for a single APP sensor, the following occurs: |
| - | The control module will not command Reduced Engine Power mode. |
| - | The control module will use the remaining two APP sensors to calculate throttle response. |
| • | If certain multiple APP sensor DTCs are set for more than one APP sensor, the following occurs: |
| - | The control module commands Reduced Engine Power mode. |
| - | The APP indicated angle is limited to a predetermined value to limit the amount of throttle control. |
| - | The message center displays Reduced Engine Power. |
| • | If all three APP sensors are out of range, the following occurs: |
| - | The control module commands Reduced Engine Power mode. |
| - | The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. |
| - | The message center displays Reduced Engine Power. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear 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 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Step 3 |
3 |
Did this DTC fail this ignition, during the above test ? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 | Is DTC P1272 also set? | -- | Go to Step 6 | Go to Step 5 |
5 | Is DTC P1273 also set? | -- | Go to Step 12 | -- |
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 16 |
7 | 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 8 | Go to Step 18 |
8 |
Is the APP sensor 1 voltage less than the specified value? | 1 V | Go to Step 15 | Go to Step 9 |
9 | Is the APP sensor 2 voltage more than the specified value? | 4 V | Go to Step 10 | Go to Step 11 |
10 | Test the APP sensor 1 signal circuit for a short to the APP sensor 3 signal circuit with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 12 |
11 | Test the APP sensor 1 signal circuit for a short to the APP sensor 2 signal circuit with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 12 |
12 |
Does the test lamp illuminate? | -- | Go to Step 13 | Go to Step 19 |
13 | 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 14 | Go to Step 20 |
14 |
Does the scan tool indicate voltage at the specified value? | 5 V | Go to Step 21 | Go to Step 15 |
15 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
16 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
17 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
18 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
19 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
20 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
21 | Inspect for poor connections at the harness connector of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 22 |
22 | Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- |
23 | Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 24 |
24 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- |
25 |
Does the DTC run and pass? | -- | Go to Step 26 | Go to Step 2 |
26 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
