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P2138






P2138-ACCELERATOR PEDAL POSITION SENSOR 1/2 CORRELATION

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The Electronic Throttle Control (ETC) system uses two Accelerator Pedal Position (APP) Sensors to monitor the accelerator pedal position. The APP Sensors 1 and 2 are integrated into one assembly located at the pedal assembly. Each sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The Powertrain Control Module (PCM) reads the two signals individually and then compares the two signals as a redundant check of the throttle position. One of the sensors will fluctuate between 0 volts and 5.0 volts and the other sensor will fluctuate between 0 volts and 2.5 volts. The fluctuation of the two sensors should move proportionately. E.G. When operating properly, the voltage reading of the sensor operating on the 5.0 volt scale will always approximately two time the voltage reading of the sensor on the 2.5 volts scale.

- When Monitored:
With the ignition on, battery voltage greater than 10.4 Volts, and no APPS 1 and APPS 2 DTCs present.

- Set Condition:
The Powertrain Control Module (PCM) detects that the correlation between APPS 1 and APPS 2 is not plausible. Idle may be affected when the brake pedal is pressed or if a brake switch circuit error is present. Acceleration rate and engine output are limited. One trip fault and the code will set within five seconds. ETC light is flashing. If the vehicle is equipped with the stop/start feature, the system will be disabled when this DTC is active.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. DTC IS ACTIVE

NOTE: Diagnose and repair any APPS, system voltage, or sensor supply voltage DTCs before continuing with this test.

1. Start the engine and allow it to reach normal operating temperature.

WARNING:
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

2. With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. (K852) 5-VOLT SUPPLY CIRCUIT OPEN OR HIGH RESISTANCE




1. Turn the ignition off.
2. Disconnect the Accelerator Pedal Position Sensor harness connector.
3. Disconnect the Powertrain Control Module (PCM) C1 harness connector.
4. Measure the resistance of the (K852) 5-Volt Supply circuit between the Accelerator Pedal Position Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 3

No

- Repair the (K852) 5-Volt Supply circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. (K23) APP SENSOR SIGNAL 1 CIRCUIT OPEN OR HIGH RESISTANCE




1. Measure the resistance of the (K23) APP Sensor Signal 1 circuit between the Accelerator Pedal Position Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the (K23) APP Sensor signals 1 circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. (K167) APP SENSOR GROUND 1 CIRCUIT OPEN OR HIGH RESISTANCE




1. Measure the resistance of the (K167) APP Sensor Ground 1 circuit between the Accelerator Pedal Position Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 5

No

- Repair the (K167) APP Sensor Ground 1 circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. (K854) 5-VOLT SUPPLY CIRCUIT OPEN OR HIGH RESISTANCE




1. Measure the resistance of the (K854) 5 Volt Supply circuit between the Accelerator Pedal Position Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 6

No

- Repair the (K854) 5 Volt Supply circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. (K29) APP SIGNAL 2 CIRCUIT OPEN OR HIGH RESISTANCE




1. Measure the resistance of the (K29) APP Signal 2 circuit between the Accelerator Pedal Position Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 7

No

- Repair the (K29) APP Signal 2 circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

7. (K400) APP SENSOR GROUND 2 CIRCUIT OPEN OR HIGH RESISTANCE




1. Measure the resistance of the (K400) APP Sensor Ground 2 circuit between the Accelerator Pedal Position Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 8

No

- Repair the (K400) APP Sensor Ground 2 circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

8. ACCELERATOR PEDAL POSITION SENSOR
1. Turn the ignition off.
2. Connect the Accelerator Pedal Position Sensor harness connector.
3. Connect the Powertrain Control Module (PCM) C1 harness connector.
4. Turn the ignition on.
5. Set up a lab scope to view two graphs simultaneously.
6. Using one channel on the lab scope, backprobe the (K23) APP Signal 1 circuit at the APP Sensor harness connector.
7. Using the other channel on the lab scope, backprobe the (K29) APP Signal 2 circuit at the APP Sensor harness connector.
8. Slowly press and release the Accelerator Pedal while monitoring the lab scope screen.

Does the scope pattern show any missing or erratic signals?

Yes

- Replace the Accelerator Pedal Position Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 9

9. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Accelerator Pedal Position Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module (PCM). Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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