P0123
(P0123) APPS SIGNAL #1 CIRCUIT HIGH
When Monitored and Set Condition
^ When Monitored: With the ignition on and no other Accelerator Pedal Position Sensor (APPS) #1 DTCs present.
^ Set Condition: When APPS #1 voltage is too high. Engine will only idle if the Brake pedal is pressed or has failed. Acceleration rate and Engine output are limited.
POSSIBLE CAUSES
INTERMITTENT CONDITION
ACCELERATOR PEDAL POSITION SENSOR #1 SWEEP
ACCELERATOR PEDAL POSITION SENSOR #1 SIGNAL CIRCUIT SHORTED TO VOLTAGE
ACCELERATOR PEDAL POSITION SENSOR #1 SIGNAL SHORTED TO 5-VOLT SUPPLY CIRCUIT
ACCELERATOR PEDAL POSITION SENSOR #1 GROUND CIRCUIT OPEN
ACCELERATOR PEDAL POSITION SENSOR (APPS) #1
POWERTRAIN CONTROL MODULE
Diagnostic Test
1. APPS #1 VOLTAGE ABOVE 3.5 VOLTS
Turn the ignition on.
With the DRB III in Sensors, read the APPS voltage.
Is the voltage above 3.5 volts?
Yes>> Go To 2
No>> Go To 7
2. APPS
Turn the ignition off.
Disconnect the APPS harness connector.
Note: Check connectors-Clean/repair as necessary.
Turn the ignition on.
Connect a jumper wire between the APPS 5-Volt Supply circuit and the APPS Signal #1 circuit at the APPS harness connector.
With the DRB III, monitor the APPS #1 voltage.
Is the voltage below 2.0 volts?
Yes>> Replace the Accelerator Pedal Position Sensor.
Perform Powertrain Verification Test - Ver 2
No>> Go To 3
3. APPS #1 SIGNAL CIRCUIT SHORTED TO VOLTAGE
Turn the ignition off.
Disconnect the PCM C4 harness connector.
Note: Check connectors-Clean/repair as necessary.
Turn the ignition on.
Measure the voltage of the APPS #1 Signal circuit at the APPS harness connector.
Is the voltage above 1.0 volt?
Yes>> Repair the APPS #1 Signal circuit for a short to voltage.
Perform Powertrain Verification Test - Ver 2
No>> Go To 4
4. APPS #1 SIGNAL CIRCUIT SHORTED TO 5-VOLT SUPPLY CIRCUIT
Turn the ignition off.
Measure the resistance of the APPS #1 Signal circuit and the 5-Volt Supply circuit at the APPS harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the APPS #1 Signal circuit for a short to the 5-Volt Supply circuit.
Perform Powertrain Verification Test - Ver 2
No>> Go To 5
5. OPEN APPS #1 GROUND CIRCUIT
With the ignition off.
Measure the resistance of the APPS #1 Ground circuit from the APPS harness connector to the PCM C4 harness connector.
Is the resistance below 5.0 ohms?
Yes>> Go To 6
No>> Repair the APPS #1 Ground circuit for an open.
Perform Powertrain Verification Test - Ver 2
6. 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.
If there are no possible causes remaining, view repair.
Repair>> Replace and program the Powertrain Control Module.
Perform Powertrain Verification Test - Ver 2
7. APPS #1 SWEEP
With the ignition on.
With the DRB III, monitor the APPS #1 voltage.
Slowly open the throttle from the idle position to the wide open throttle position.
Does voltage start at approximately 0.1 of a volt and go above 2.5 volts with a smooth transition?
Yes>> Go To 8
No>> Replace the Accelerator Pedal Position Sensor.
Perform Powertrain Verification Test - Ver 2
8. INTERMITTENT WIRING AND CONNECTORS
The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.
Note: Check connectors-Clean/repair as necessary. Poor pin to terminal connections can set DTCs.
Note: Check for any Technical Service Bulletins that may apply. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors specific to this DTC. Wiggle the wires while checking for shorts and open circuits.
Were there any problems found?
Yes>> Repair as necessary.
Perform Powertrain Verification Test - Ver 2
No>> The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.