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 5.0 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 1.1 volt at 0% pedal travel (pedal at rest) to above 2.1 volts at 100% pedal travel (pedal fully depressed). The APP sensor 2 signal decreases from above 3.9 volts at 0% pedal travel to below 2.9 volts at 100% pedal travel. The APP sensor 3 signal decreases from above 3.2 volts at 0% pedal travel to below 3.1 volts at 100% pedal travel. Observe that the signal circuits for APP Sensor 2 and APP Sensor 3 pull up to 5.0 volts and the APP Sensor 1 signal circuit pull to ground within the TAC Module.
Conditions For Running the DTC
| • | DTCs P1517, P1518 not set. |
| • | Ignition switch in the crank or run position. |
| • | Ignition voltage greater than 5.23 volts. |
Conditions for Setting the DTC
| • | APP sensor #3 disagrees with APP sensor #1 by more than 13.0% and APP sensor #3 disagrees with APP sensor #2 by more than 13.0%. |
| • | 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.
| • | The following may cause an intermittent: |
| - | Poor connections: Check for adequate terminal tension. Refer to Wiring Repairs 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 and TP sensor 5.0 volt reference circuits are internally connected within the TAC. Inspect the 5.0 volt reference circuits at the APP and the TP sensors for an open, a ground, or a short to a voltage. TP and APP sensor DTCs will set. |
| • | For an intermittent condition, refer to Symptoms . |
| • | If you complete a repair and the DTC is 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 5.0 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 captured DTC info.
Step | Action | Value(s) | 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.
Are all three parameters at the specified value? | 0% | ||
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 |
Did this DTC set? | -- | Go to Diagnostic Aids | |
5 | Disconnect the TAC Module connector containing the APP sensor circuits. Refer to Electronic Throttle Actuator Control Module Replacement . Are all three parameters at 0%? | -- | ||
6 |
Does the DMM indicate continuity? | -- | ||
7 |
Does the DMM indicate continuity? | -- | ||
8 |
Does the DMM indicate continuity? | -- | ||
Are any of these other sensor voltages affected or does the APP sensor 3 voltage not equal the specified voltage when the circuits are connected? | 3.94-6.06V | |||
Are any of these other sensor voltages affected or does the APP sensor 3 voltage not equal the specified voltage when the circuits are connected? | 0.0-0.1V | |||
11 | Repair the signal circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
12 | Repair the circuit with the high resistance. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
13 | Check for poor connections/terminal tension at the APP sensor and at the TAC Module. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
14 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position Sensor Replacement . Is the action complete? | -- | -- | |
15 | Replace the TAC Module. Refer to Electronic Throttle Actuator Control Module Replacement . Is the action complete? | -- | -- | |
16 |
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 |
