Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 3 individual APP sensors within 1 housing. Three separate signal, low reference and 5-volt reference circuits connect the APP sensor assembly and the throttle actuator control (TAC) module. Each sensor has a unique functionality. The APP sensor 1 signal increases as the accelerator pedal is depressed, from below 1 volt at 0 percent pedal travel, with the pedal at rest, to above 2 volts at 100 percent pedal travel, with the pedal fully depressed. The APP sensor 2 signal decreases from above 4 volts at 0 percent pedal travel to below 2.9 volts at 100 percent pedal travel. The APP sensor 3 signal decreases from around 3.8 volts at 0 percent pedal travel to below 3.1 volts at 100 percent pedal travel. Notice that the signal circuits for APP sensor 2 and APP sensor 3 pull up to 5 volts and the APP sensor 1 signal circuit is referenced to low reference within the TAC module.
Conditions for Running the DTC
| • | DTCs P0606, P1517, or P1518 are not set. |
| • | The ignition switch is in the crank or run position. |
| • | The ignition voltage is greater than 5.23 volts. |
Conditions for Setting the DTC
| • | APP sensor 3 disagrees with APP sensor 1 by more than 13 percent and APP sensor 3 disagrees with APP sensor 2 by more than 13 percent. |
| • | All of the above conditions are 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. |
Diagnostic Aids
| • | Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing. |
| • | When the TAC module detects throttle movement with a DTC P1285 set, a DTC P1286 also sets. |
| • | When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info. |
| • | For an intermittent, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
This step determines if a communication condition exists.
-
This step isolates an internal APP sensor failure. The condition may only occur at a certain accelerator pedal position. Monitoring the APP angles for sensor 1 and sensor 2 is an accurate way of verifying the actual position of the pedal. The APP angles for all 3 sensors should be within a few percent of each other. When the pedal is at rest, the APP angle for all 3 sensors should be 0 percent. When the pedal is fully depressed, all APP angles should be 100 percent.
-
The APP sensor 3 has a dedicated 5-volt reference circuit. Monitoring the APP sensor 1 voltage aids in diagnosing the APP sensor 3 5-volt reference circuit. If the scan tool displays 5 volts then the circuits are OK.
-
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views , Electronic Throttle Actuator 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 | |
Is DTC P1518 also set? | -- | Go to DTC P1518 | Go to Step 3 | |
3 |
Important: Do not depress the accelerator pedal.
Did any other TAC module or APP sensor DTCs set except DTC P1125? | -- | Go to Step 4 | |
4 | With a scan tool, observe the APP sensor Agree/Disagree parameters. Does the scan tool indicate Disagree for any of the APP sensor Agree/Disagree parameters? | -- | Go to Step 6 | Go to Step 5 |
Does the scan tool indicate that the APP sensor 3 angle is within 13 percent of both APP sensors 1 and 2 angles? | -- | Go to Diagnostic Aids | Go to Step 6 | |
Does the DMM indicate voltage within the specified values? | 3.94-6.06 V | Go to Step 7 | Go to Step 14 | |
7 | With a DMM, test the APP sensor 3 signal circuit for voltage. Does the DMM indicate voltage within the specified values | 3.94-6.06 V | Go to Step 8 | Go to Step 16 |
8 | With a DMM connected between the APP sensor 3 low reference circuit and the APP sensor 1 low reference circuit, measure the resistance. Does the DMM indicate resistance within the specified values? | 0-5 ohms | Go to Step 9 | Go to Step 19 |
9 |
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 10 |
10 | With a DMM, test for a short between the APP sensor 3 5-volt reference circuit and all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 11 |
11 | With a DMM, test the APP sensor 3 signal circuit 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 24 | Go to Step 12 |
12 | With a DMM, test for a short between the APP sensor 3 signal circuit and all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 13 |
13 | With a DMM, test the APP sensor 3 low reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 20 |
14 |
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 15 |
15 | With a DMM, test the APP sensor 3 5-volt reference circuit 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 24 | Go to Step 21 |
16 |
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 17 |
17 | With a DMM, test the APP sensor 3 signal circuit 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 24 | Go to Step 18 |
18 | With a DMM, test for a short between the APP sensor 3 signal circuit and all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 19 |
19 |
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 21 |
20 | 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 24 | Go to Step 22 |
21 | Inspect for poor connections at the harness connectors of the TAC module. 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 24 | Go to Step 23 |
22 | Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 24 | -- |
23 | Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement . Did you complete the replacement? | -- | Go to Step 24 | -- |
24 |
Does the DTC run and pass? | -- | Go to Step 25 | Go to Step 2 |
With a scan tool, observe the stored information, Capture info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | ||
