Engine Code
SYMPTOM
P0123-THROTTLE POSITION SENSOR 1 CIRCUIT HIGH (3.7L, 4.7L)
WHEN MONITORED
With the ignition on. Battery voltage greater than 10.4 volts.
SET CONDITION
Throttle Position Sensor voltage at the PCM is greater than 4.47 volts for 1.3 seconds. One Trip Fault. Three good trips to turn off the MIL.
POSSIBLE CAUSES
- (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
- (K22) TP SENSOR NO.1 SIGNAL CIRCUIT OPEN
- (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO THE (F855) 5-VOLT SUPPLY CIRCUIT
- (K900) SENSOR GROUND CIRCUIT OPEN
- THROTTLE POSITION SENSOR
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures
DIAGNOSTIC TEST
1. TP SENSOR VOLTAGE ABOVE 4.5 VOLTS
Note: Make sure the throttle is fully closed and free from binding or carbon build up.
Start the engine.
With a scan tool, read the TP Sensor voltage.
Is the voltage above 4.5 volts?
Yes>> Go To 2
No>> Go To 8
2. THROTTLE POSITION SENSOR
Turn the ignition off.
Disconnect the TP Sensor harness connector.
Connect a jumper wire between the (K22) TP Sensor No.1 Signal circuit and the (K900) Sensor ground circuit in the Sensor harness connector.
With a scan tool, monitor the TP Sensor voltage.
Ignition on, engine not running.
Is the voltage below 0.5 of a volt with the jumper wire installed?
Yes>> Replace the Throttle Position Sensor. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5. Powertrain Verification Test - Ver 5
No>> Go To 3
Note: Remove the jumper wire before continuing.
3. (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the PCM harness connectors.
Ignition on, engine not running.
Measure the voltage on the (K22) TP Sensor No.1 Signal circuit in the TP Sensor harness connector.
Is the voltage above 5.2 volts?
Yes>> Repair the short to battery voltage in the (K22) TP Sensor No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 4
4. (K22) TP SENSOR NO.1 SIGNAL CIRCUIT OPEN
Turn the ignition off.
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 (K22) TP Sensor No.1 Signal circuit from the TP 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 (K22) TP Sensor No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
5. (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO THE (F855) 5-VOLT SUPPLY CIRCUIT
Measure the resistance between the (K22) TP Sensor No.1 Signal circuit and the (F855) 5-volt Supply circuit in the TP Sensor harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the short between the (F855) 5-volt Supply circuit and the (K22) TP Sensor No.1 Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 6
6. (K900) SENSOR GROUND CIRCUIT OPEN
Measure the resistance of the (K900) Sensor ground circuit from the TP Sensor harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms?
Yes>> Go To 7
No>> Repair the open in the (K900) Sensor ground circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
7. 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 (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
8. THROTTLE POSITION SENSOR SWEEP
With a scan tool, monitor the Throttle Position Sensor voltage.
Slowly open the throttle from the idle position to the wide open throttle position.
Does voltage start at approximately 0.8 of a volt and go above 3.5 volts with a smooth transition?
Yes>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Replace the Throttle Position Sensor. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.