Accelerator Pedal Position (APP) Sensor
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 Setting the DTC
| • | P1517, P1518 not set. |
| • | Ignition switch in the crank or run position. |
| • | Ignition voltage greater than 5.23 volts. |
| • | APP sensor #2 voltage is less than 0.83 volts or greater than 4.81 volts. |
| • | All 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 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 Body and Accessories/Wiring Systems for proper procedure. |
| - | Corrosion |
| - | Mis-routed harness |
| - | Rubbed through wire insulation |
| - | Broken wire inside the insulation |
| - | Inspect the TAC module connectors for signs of water intrusion. This causes intermittent DTCs. |
| • | 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 throttle movement with a DTC P1280 set, a DTC P1281 also sets. |
| • | 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.
-
This test determines whether or not the TAC Module can recognize a change in signal voltage.
-
There are three separate 5.0 volt reference sources within the TAC Module. TP Sensor 1 and APP Sensor 1 share one 5.0 volt reference source, TP Sensor 2 and APP Sensor 2 share another common 5.0 volt reference source and APP Sensor 3 uses the third by itself. This test determines whether the signal circuit is shorted to any one of the 5.0 volt reference circuits. If a short exists, the corresponding sensor voltage will be pulled low.
-
The previous step found the signal circuit and a 5.0 volt reference circuit shorted together. This test isolates whether the short is in the harness or within the TAC Module.
-
When a problem is detected 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. It is possible that 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.
Is the voltage within the specified range? | 3.90-4.81 V | ||
3 | Fully depress the accelerator pedal. Is the voltage within the specified range? | 0.83-2.90 V | ||
4 |
Does the harness movement cause this DTC to set? | -- | ||
5 |
Did this DTC set? | -- | Go to Diagnostic Aids | |
6 |
Is the voltage within the specified range? | 3.94-6.06 V | ||
7 |
Is any voltage present? | -- | ||
8 | Check the harness of the APP Sensor 2 signal circuit for continuity using the DMM J 39200 . Is continuity indicated? | -- | ||
9 | Check the harness for continuity between the APP Sensor 2 signal circuit and the battery ground using the DMM J 39200 . Is continuity indicated? | -- | ||
10 | Check the harness for continuity between the APP Sensor 2 signal circuit, at the TAC harness connector, and all other circuits in both TAC module connectors using the DMM J 39200 . Is continuity indicated? | -- | ||
11 | Measure the voltage from the APP Sensor 2 5.0 volt reference circuit in the APP Sensor harness connector to battery ground using the DMM J 39200 . Is the voltage within the specified range? | 3.94-6.06 V | ||
12 |
Is any voltage present? | -- | ||
13 | Check the harness for continuity of the APP Sensor 2 5.0 volt reference circuit using the DMM J 39200 . Is continuity indicated? | -- | ||
14 | Check the harness for continuity between the APP Sensor 2 5.0 volt reference circuit and battery ground using the DMM J 39200 . Is continuity indicated? | -- | ||
15 | Check the harness for continuity between the APP Sensor 2 5.0 volt reference circuit, at the TAC harness connector, and all other circuits in both TAC module connectors using the DMM J 39200 . Is continuity indicated? | -- | ||
16 | Measure the resistance from the APP Sensor 2 ground circuit in the APP Sensor harness connector to battery ground using the DMM J 39200 . Is the resistance within the specified range? | 0-5 ohms | ||
17 |
Is continuity indicated? | -- | ||
Does the scan tool indicate the specified voltage? | 0 V | |||
Are any of these other sensor voltages affected when the APP Sensor 2 signal circuit is grounded? | -- | |||
Is continuity indicated? | -- | |||
21 | Repair harness/connections as necessary. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
22 | Repair the short to voltage in the 5.0 volt reference circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
23 | Repair the open/high resistance in the 5.0 volt reference circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
24 | Repair the short to ground in the 5.0 volt reference circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
25 | Repair the signal circuit shorted to voltage. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
26 | Repair the open/high resistance in the signal circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
27 | Repair the short to ground in the signal circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
28 | Repair the open/high resistance in the ground circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
29 | Repair the circuits that are shorted together. Is the action complete? | -- | -- | |
30 | Check for poor connections/terminal tension at the APP Sensor harness connector. Refer to Body and Accessories/Wiring Systems for proper procedure. Was a problem found and corrected? | -- | ||
31 | Replace the accelerator pedal assembly. Refer to Accelerator Pedal Assembly . Is the action complete? | -- | -- | |
32 | Check for poor connections/terminal tension at the TAC Module harness connector. Refer to Body and Accessories/Wiring Systems for proper procedure. Was a problem found and corrected? | -- | ||
33 | Replace the TAC Module. Refer to Electronic Throttle Actuator Control Module Replacement . Is the action complete? | -- | -- | |
34 |
Does the scan tool indicate that this test 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 |
