Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 3 individual APP sensors within one housing. Three separate signal, ground, 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 1.1 volt at 0 percent pedal travel (pedal at rest) to above 2.1 volts at 100 percent pedal travel (pedal fully depressed). The APP sensor 2 signal decreases from above 3.9 volts at 0 percent pedal travel to below 2.9 volts at 100 percent pedal travel. The APP sensor 3 signal decreases from above 3.2 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 pull to ground within the TAC module.
Conditions For Running the DTC
| • | DTCs P1517, P1518 are not set. |
| • | The ignition is in the crank or run position. |
| • | The ignition voltage is more than 5.23 volts. |
Conditions for Setting the DTC
| • | APP sensor 1 disagrees with APP sensor 2 by more than 10.5 percent and APP sensor 1 disagrees with APP sensor 3 by more than 13.0 percent . |
| • | All 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 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 either defaults to a Reduced Engine Power Mode or to a more tightly restricted mode of operation if the TAC determines that limited safe operation is possible, or the TAC commands the engine to shut down. |
Conditions for Clearing the MIL/DTC
| • | 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. |
| • | A last test failed (Current DTC) will clear when the diagnostic runs and does not fail. |
| • | The PCM battery voltage is interrupted. |
| • | Use a scan tool in order to clear the MIL/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. |
| • | Inspect the PCM\TAC module connector gaskets. Refer to Powertrain Control Module Controlled Tachometer Diagnosis . |
| • | Inspect for the following conditions that may cause an intermittent: |
| - | Poor connections |
| - | Inadequate terminal tension |
| - | Corrosion |
| - | Misrouted or damaged harness |
| - | Rubbed through wire insulation |
| - | Broken wire inside the insulation |
| - | Water intrusion |
| • | Inspect the TAC module connectors for signs of water intrusion. |
| • | Inspect for further causes of intermittents. Refer Symptoms . |
| • | If you complete a repair and the DTC was cleared using a scan tool on the same ignition cycle, the default action will not clear until an ignition cycle has occurred. |
| • | 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Jumping one APP sensor signal circuit to 5 volts should not affect any of the other APP sensor voltages. A problem exists within the TAC module if jumping the circuits affects another APP parameter.
-
Jumping one APP sensor signal circuit to ground should not affect any of the other APP sensor voltages. A problem exists within the TAC module if jumping the circuits affects another APP parameter.
-
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 the captured DTC information.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Important: If DTC P1518 is also set, refer to DTC P1518 for further diagnosis.
Is the voltage within the specified range? | 0.25-1.10 V | ||
3 |
Does the scan tool display NO for the APP sensor 1 and 2 disagree and the APP sensor 2 and 3 disagree parameters? | -- | ||
4 |
Does the harness movement cause this DTC to fail this ignition? | -- | ||
5 |
Did this DTC fail this ignition? | -- | Go to Diagnostic Aids | |
6 | Disconnect the TAC module connector containing the APP sensor circuits. Does the scan tool indicate the specified voltage? | 0 V | ||
7 |
Does the DMM indicate continuity? | -- | ||
8 |
Does the DMM indicate continuity? | 0-5 ohms | ||
9 |
Does the DMM indicate continuity? | 0-5 ohms | ||
Are any other APP sensor voltages affected, or does the APP sensor 1 voltage not equal the specified voltage when the circuits are connected? | 3.94-6.06 V | |||
Are any other APP sensor voltages affected, or does the APP sensor 1 voltage not equal the specified voltage when the circuits are connected? | 0.0-0.1 V | |||
12 | Repair the harness/connections as necessary. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
13 | Repair the signal circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
14 | Repair the circuit with the high resistance. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
15 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Is the action complete? | -- | -- | |
16 | Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement . Is the action complete? | -- | -- | |
17 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
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 the applicable DTC Table | System OK |
