Engine Code

P0123-THROTTLE POSITION SENSOR 1 CIRCUIT HIGH






For a complete wiring diagram refer to: Electrical Diagrams

When Monitored
With the ignition on. Battery voltage greater than 10 volts.

Set Condition
Throttle Position Sensor No.1 voltage is greater than 4.8 volts for 25 ms. One Trip Fault. ETC light will illuminate.

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
- (K922) SENSOR RETURN CIRCUIT OPEN
- THROTTLE POSITION SENSOR/THROTTLE BODY
- THROTTLE PLATE JAMMED AGAINST THE MAXIMUM STOP
- PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test





1. TP SENSOR NO.1 VOLTAGE ABOVE 4.8 VOLTS

NOTE: Make sure the throttle is fully closed and free from binding or carbon build up.

NOTE: If a 5-Volt Supply DTC has also set, diagnose the 5-Volt DTC before continuing.

NOTE: If P2101 is also set, then make sure that the blade moves freely and does not hang up near Wide Open Throttle before trying to repair P0123.

Start the engine.
With a scan tool, read the TP Sensor No.1 voltage.

Is the voltage above 4.8 volts?
Yes >> Go To 2
No >> Go To 8

2. THROTTLE POSITION SENSOR





Turn the ignition off.
Disconnect the Throttle Body harness connector.
Connect a jumper wire between the (K22) TP Sensor No.1 Signal circuit and the (K922) Sensor Return circuit in the Throttle Body harness connector.
With a scan tool, monitor the TP Sensor No.1 voltage. Ignition on, engine not running.

Is the voltage below 0.5 of a volt with the jumper wire installed?
Yes >> Disconnect the Battery when replacing the Throttle Body Assembly. Replace the Throttle Body Assembly. After installation is complete, using a scan tool, select the ETC RELEARN function.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
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 Throttle Body harness connector.

Is voltage present?
Yes >> Repair the short to battery voltage in the (K22) TP Sensor No.1 Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
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 Throttle Body 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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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 Throttle Body 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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 6

6. (K922) SENSOR RETURN CIRCUIT OPEN





Measure the resistance of the (K922) Sensor Return circuit from the Throttle Body 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 (K922) Sensor Return circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Replace and program the Powertrain Control Module per Service Information.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

8. THROTTLE FOLLOWER TEST





With a scan tool, perform the Throttle Follower Test.
Monitor the TP Sensor No.1 voltage.

Does voltage start at approximately 0.3 of a volt and go above 4.7 volts with a smooth transition?
Yes >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Disconnect the Battery when replacing the Throttle Body Assembly. Replace the Throttle Body Assembly. After installation is complete, using a scan tool select the ETC RELEARN function.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test