2014 Jeep Wrangler JK Factory Service Manual 28 - DTC-Based Diagnostics

P2127-ACCELERATOR PEDAL POSITION SENSOR 2 CIRCUIT LOW

Special Tools: Click to display a list of tools used in this procedure


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.



Possible Causes

5-VOLT SUPPLY CIRCUIT OPEN OR SHORTED TO GROUND
APP SENSOR 2 SIGNAL CIRCUIT OPEN
APP SENSOR 2 SIGNAL CIRCUIT SHORTED TO GROUND
APP SENSOR 2 SIGNAL CIRCUIT SHORTED TO THE APP SENSOR 1 RETURN CIRCUIT
APP SENSOR 2 SIGNAL CIRCUIT SHORTED TO THE APP SENSOR 2 RETURN CIRCUIT
APP SENSOR 2 GROUND CIRCUIT OPEN OR HIGH RESISTANCE
APP SENSOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).


1. ACTIVE DTC



NOTE: Diagnose and repair any 5-Volt Sensor supply voltage DTCs before continuing with this test.
1. Turn the ignition on.
2. With the scan tool, read DTCs.


Is the DTC Active or Pending at this time?

Yes


No


2. CHECK THE (K854) 5-VOLT SUPPLY CIRCUIT VOLTAGE

1. Turn the ignition off.
2. Disconnect the Accelerator Pedal Position Sensor harness connector.
3. Turn the ignition on.
4. Measure the voltage of the (K854) 5-Volt Supply circuit in the Accelerator Pedal Position Sensor harness connector.


Is the voltage between 4.9 and 5.2 volts?

Yes


No


3. CHECK THE (K29) APP SENSOR 2 SIGNAL CIRCUIT FOR A SHORT TO GROUND

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


Is the resistance above 10k Ohms?

Yes


No


4. CHECK FOR THE (K29) APP SENSOR 2 SIGNAL CIRCUIT SHORTED TO THE SENSOR GROUND CIRCUITS

1. Measure the resistance between the (K29) APP Sensor 2 Signal circuit and the:

  • (K400) Sensor Ground circuit in the Accelerator Pedal Position Sensor harness connector.
  • (K167) Sensor Ground circuit in the Accelerator Pedal Position Sensor harness connector.


Is the resistance above 10k Ohms?

Yes


No


5. CHECK THE (K29) APP SENSOR 2 SIGNAL CIRCUIT FOR AN OPEN OR HIGH RESISTANCE

CAUTION:

Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.

1. Connect the Adapter, GPEC Diagnostic 10436 .
2. Measure the resistance of the (K29) APP Sensor 2 Signal circuit between the Accelerator Pedal Position Sensor harness connector and the GPEC Adaptor.


Is the resistance below 5.0 Ohms?

Yes


No


6. CHECK THE (K400) APP SENSOR GROUND 2 CIRCUIT FOR AN 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 GPEC Adaptor.


Is the resistance below 5.0 Ohms?

Yes


No


7. CHECK THE ACCELERATOR PEDAL POSITION SENSOR

1. Reconnect the PCM C1 harness connector.
2. Connect a jumper between the (K854) 5-Volt Supply circuit and the (K29) APP Sensor 2 Signal circuit in the Accelerator Pedal Position Sensor harness connector.
3. Turn the ignition on.
4. With the scan tool, read the Accelerator Pedal Position Sensor signal voltage.


Is the voltage above 4.9 volts with the jumper in place?

Yes


No


8. 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


No