Refer to
Cell 20: TP and APP Sensors
for complete circuit details.
Circuit Description
The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually three individual Accelerator Pedal Position sensors within one housing. Three separate signal, ground and 5 volt reference circuits connect the Accelerator Pedal Position 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 1.0 volt at 0 percent pedal travel (pedal at rest) to above 2.0 volts at 100 percent pedal travel (pedal fully depressed). The APP sensor 2 signal decreases from above 4.0 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. Observe 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 ground within the TAC Module.
Conditions for Running the DTC
| • | DTCs P0606, P1517, 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 met for less than 1 second. |
Action Taken When the DTC Sets
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records. |
| • | If no other TAC System DTCs are set, the TAC System operates normally. If certain TAC System DTCs are set at the same time, the TAC system commands the engine to operate in a reduced engine power mode. The TAC system may command the engine to shut down. |
Conditions for Clearing the DTC
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
Important:
• Remove any debris from the PCM\TAC module connector surfaces before
servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets
when diagnosing/replacing the modules. Ensure that the gaskets are
installed correctly. The gaskets prevent contaminate intrusion into
the PCM\TAC modules. • For any test that requires probing the PCM or a component
harness connector, use the Connector Test Adapter Kit J 35616
. Using this kit prevents damage
to the harness/component terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
| • | The following may cause an intermittent: |
| - | Poor connections; Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. |
| - | Corrosion |
| - | Mis-routed harness |
| - | Rubbed through wire insulation |
| - | Broken wire inside the insulation |
| - | Inspect the TAC module connectors for signs of water intrusion. When this occurs, multiple DTCs should set and you cannot locate any circuit or component problems. |
| • | The APP sensor 1 and the TP sensor 1 5.0 volt reference circuits are internally connected within the TAC module. |
| • | The APP sensor 2 and the TP sensor 2 5.0 volt reference circuits are internally connected within the TAC module. |
| • | When the TAC module detects a problem within the TAC System, more than one TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info. |
| • | For an intermittent condition, refer to Symptoms . |
Test description
The numbers below refer to the steps 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.
-
This step determines whether the TAC module or a shorted circuit is causing the condition.
-
Excessive resistance in the circuit causes this DTC to set.
-
Excessive resistance in the circuit causes this DTC to set.
-
Excessive resistance in the circuit causes this DTC to set.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Is DTC P1518 also set? | -- | Go to DTC P1518 Throttle Actuator Control (TAC) Module Serial Data Circuit | ||
3 |
Important: Do not depress the accelerator pedal.
Did any other TAC Module or APP sensor DTCs set except P1125? | -- | Go to Applicable DTC | |
4 | Monitor the APP sensor disagree parameter using the scan tool. Does the scan tool display YES for any of the disagree parameters? | -- | ||
Does the APP sensor 3 angle correspond to the APP sensors 1 and 2 angles? | -- | Go to Diagnostic Aids | ||
Does the scan tool display the specified value? | 5V | |||
7 |
Does the scan tool display near the specified value? | 0V | ||
8 |
Does the scan tool display the specified value? | 0V | ||
9 |
Does the DMM display continuity within the specified range? | 0-5ohms | ||
Does the DMM indicate continuity to any other circuit? | -- | |||
Does the DMM display continuity within the specified range? | 0-5ohms | |||
Does the DMM display continuity within the specified range? | 0-5ohms | |||
Does the DMM display continuity within the specified range? | 0-5ohms | |||
14 |
Did you find and correct the condition? | -- | ||
15 |
Did you find and correct the condition? | -- | ||
16 | Repair the open or excessive resistance in the affected circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
17 | Repair the shorted circuits that displayed continuity. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
18 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Is the action complete? | -- | -- | |
19 | Replace the TAC module. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement . Is the action complete? | -- | -- | |
20 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
21 | Select the Capture Info option and the review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
