P2127
P2127-ACCELERATOR PEDAL POSITION SENSOR 2 CIRCUIT LOW
For a complete wiring diagram refer to: Electrical Diagrams
When Monitored
With the ignition on and no other APPS No.2 DTCs present.
Set Condition
When the APP Sensor No.2 voltage is too low. Engine will only idle if the Brake pedal is Pressed or has failed. Acceleration rate and Engine output are limited. One trip fault and the code will set within 5 seconds. ETC light is flashing.
Possible Causes
- (F856) 5-VOLT SUPPLY CIRCUIT OPEN
- (F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
- (K29) APP SENSOR NO.2 SIGNAL CIRCUIT OPEN
- (K29) APP SENSOR NO.2 SIGNAL CIRCUIT SHORTED TO GROUND
- (K29) APP SENSOR NO.2 SIGNAL CIRCUIT SHORTED TO THE (K167) APP SENSOR NO.1 RETURN CIRCUIT
- (K29) APP SENSOR NO.2 SIGNAL CIRCUIT SHORTED TO THE (K400) APP SENSOR NO.2 RETURN CIRCUIT
- APP SENSOR
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. APP SENSOR BELOW 0.25 OF A VOLT
Ignition on, engine not running.
With a scan tool, read the APP Sensor No.1 voltage.
NOTE: Sensor No. 2 is pulled low by the PCM as part of its system testing. This test happens a couple of times a second. So you can expect to see voltages close to zero occasionally with a normal sensor.
Is the voltage consistently below 0.25 of a volt?
Yes >> Go To 2
No >> Go To 11
2. (F856) 5-VOLT SUPPLY CIRCUIT
Turn the ignition off.
Disconnect the APP Sensor harness connector. Ignition on, engine not running.
Measure the voltage on the (F856) 5-volt Supply circuit in the APP Sensor harness connector.
Is the voltage between 4.5 and 5.2 volts?
Yes >> Go To 3
No >> Go To 8
3. ACCELERATOR PEDAL POSITION SENSOR
Connect a jumper wire between the (F856) 5-volt Supply circuit and the (K29) APP Sensor No.2 Signal circuit in the Sensor harness connector.
With a scan tool, monitor the APP Sensor No.2 voltage.
Is the voltage above 4.5 volts with the jumper wire installed?
Yes >> Replace the APP Sensor Assembly per Service Information. After installation is complete, use a scan tool and select the ETC RELEARN function to relearn the APPS values.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 4
NOTE: Remove the jumper wire before continuing.
4. (K29) APP SENSOR NO.2 SIGNAL CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connectors.
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 Miller Special Tool #8815 to perform diagnosis.
Measure the resistance of the (K29) APP Sensor No.2 Signal circuit from the APP Sensor harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
Yes >> Go To 5
No >> Repair the open in the (K29) APP Sensor No.2 Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
5. (K29) APP SENSOR NO.2 SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K29) APP Sensor No.2 Signal circuit in the APP Sensor harness connector.
Is the resistance below 100 ohms?
Yes >> Repair the short to ground in the (K29) APP Sensor No.2 Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 6
6. (K29) APP SENSOR NO.2 SIGNAL CIRCUIT SHORTED TO THE (K400) APP SENSOR NO.2 RETURN CIRCUIT
Measure the resistance between the (K29) APP Sensor No.2 Signal circuit and the (K400) Sensor No.2 Return circuit in the APP Sensor harness connector.
Is the resistance below 100 ohms?
Yes >> Repair the short between the (K400) APP Sensor No.2 Return circuit and the (K29) APP Sensor No.2 Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 7
7. (K29) APP SENSOR NO.2 SIGNAL CIRCUIT SHORTED TO THE (K167) APP SENSOR NO.1 RETURN CIRCUIT
Measure the resistance between the (K29) APP Sensor No.2 Signal circuit and the (K167) Sensor No.1 Return circuit in the APP Sensor harness connector.
Is the resistance below 100 ohms?
Yes >> Repair the short between the (K167) APP Sensor No.1 Return circuit and the (K29) APP Sensor No.2 Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 10
8. (F856) 5-VOLT SUPPLY CIRCUIT OPEN
Turn the ignition off. Disconnect the PCM harness connectors.
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 Miller Special Tool #8815 to perform diagnosis.
Measure the resistance of the (F856) 5-volt Supply circuit from the Sensor harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
Yes >> Go To 9
No >> Repair the open in the (F856) 5-volt Supply circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
9. (F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (F856) 5-volt Supply circuit in the APP Sensor harness connector.
Is the resistance below 100 ohms?
Yes >> Repair the short to ground in the (F856) 5-volt Supply circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 10
10. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes >> Repair as necessary
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Replace and program the Powertrain Control Module per Service Information.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
11. APP SENSOR SWEEP
Ignition on, engine not running.
With a scan tool, monitor the APP Sensor No.2 voltage.
Slowly press the Accelerator pedal down.
Does voltage start at approximately 0.22 of a volt and go above 2.31 volts with a smooth transition?
Yes >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Replace the APP Sensor Assembly per Service Information. After installation is complete, use a scan tool and select the ETC RELEARN function to relearn the APPS values.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test