Operation CHARM: Car repair manuals for everyone.

Engine






P0123 - Throttle Position Sensor 1 Circuit High, 4.0L






For wiring diagrams, refer to.

When Monitored: With the engine running and battery voltage greater than 10 volts.

Set Condition: The PCM detects that the sensor input voltage is more than the maximum acceptable value.






Always perform the pre-diagnostic troubleshooting procedure before proceeding. Refer to => Non-DTC Based Diagnostics. Pre-Diagnostic Troubleshooting Procedure

Test Step 1 - DTC is Active

Diagnose and repair any APP sensor circuit, throttle body circuit, system voltage, or sensor supply voltage DTCs before continuing with this test.

Start the engine and allow it to reach operating temperature.


When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

With the scan tool select view DTCs.

It may be necessary to test drive the vehicle in order for this DTC to reset.

Is the status active for this DTC?

Yes

Go to Test Step 2 => [ Test
Step 2 - 5 Volt Supply Circuit Shorted to Voltage ]

No

Refer to the checking for an intermittent DTC diagnostic procedure. Refer to => Non-DTC Based Diagnostics. Checking for an Intermittent DTC

Test Step 2 - 5 Volt Supply Circuit Shorted to Voltage






Turn the ignition OFF.

Disconnect the throttle body connector.

Disconnect the C2 PCM harness connector.

Turn the ignition ON.

Measure the voltage of the 5 volt supply circuit in the throttle body harness connector.

Is there any voltage present?

Yes

Repair the short to voltage in the 5 volt supply circuit.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

No

Go to Test Step 3 => [ Test
Step 3 - TP Signal 1 Circuit Shorted to Voltage ]

Test Step 3 - TP Signal 1 Circuit Shorted to Voltage






Measure the voltage of the TP signal 1 circuit in the throttle body harness connector.

Is there any voltage present?

Yes

Repair the short to voltage in the TP signal 1 circuit.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

No

Go to Test Step 4 => [ Test
Step 4 - TP Signal 1 Circuit Shorted to 5 Volt Supply Circuit ]

Test Step 4 - TP Signal 1 Circuit Shorted to 5 Volt Supply Circuit






Turn the ignition OFF.

Measure the resistance between the TP signal 1 circuit and the 5 volt supply in the throttle body harness connector.

Is the resistance less than 100 ohms?

Yes

Repair the short between the TP signal 1 circuit and the 5 volt supply circuit.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

No

Go to Test Step 5 => [ Test
Step 5 - TP Signal 1 Circuit Shorted to ETC Motor (+) Circuit ]

Test Step 5 - TP Signal 1 Circuit Shorted to ETC Motor (+) Circuit






Measure the resistance between the TP signal 1 circuit and the ETC motor (+) in the throttle body harness connector.

Is the resistance less than 100 ohms?

Yes

Repair the short between the TP signal 1 circuit and the ETC motor (+) circuit.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

No

Go to Test Step 6 => [ Test
Step 6 - TP Signal 1 Circuit Shorted to ETC Motor (-) Circuit ]

Test Step 6 - TP Signal 1 Circuit Shorted to ETC Motor (-) Circuit






Measure the resistance between the TP signal 1 circuit and the ETC motor (-) in the throttle body harness connector.

Is the resistance less than 100 ohms?

Yes

Repair the short between the TP signal 1 circuit and the ETC motor (-) circuit.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

No

Go to Test Step 7 => [ Test
Step 7 - TP Signal 1 Circuit Open ]

Test Step 7 - TP Signal 1 Circuit Open







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 TP signal 1 circuit between the throttle body harness connector and the appropriate terminal of special tool #8815.

Is the resistance less than 5.0 ohms?

Yes

Go to Test Step 8 => [ Test
Step 8 - TP Sensor Ground Circuit Open ]

No

Repair the open in the TP signal 1 circuit.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

Test Step 8 - TP Sensor Ground Circuit Open






Measure the resistance of the TP sensor ground circuit between the throttle body harness connector and the appropriate terminal of special tool #8815.

Is the resistance less than 5.0 ohms?

Yes

Go to Test Step 9 => [ Test
Step 9 - Throttle Position Sensor 1 Voltage ]

No

Repair the open in the TP sensor ground circuit.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

Test Step 9 - Throttle Position Sensor 1 Voltage






Turn the ignition OFF.

Connect the C2 PCM harness connector.

Turn the ignition ON.

With the scan tool, read the throttle position sensor 1 voltage.

The sensor voltage should be approximately 5.0 volts (plus or minus 0.1 volt) with the throttle body connector disconnected.

Turn the ignition OFF.

Connect a jumper wire between the TP signal 1 circuit and the TP sensor ground circuit in the throttle body harness connector.

Turn the ignition ON.

With a scan tool, read the throttle position sensor 1 voltage.

The sensor voltage should be approximately 0.0 volts (plus or minus 0.1 volt) with the jumper wire in place.

Does the scan tool display the voltage as described?

Yes

Go to Test Step 10 => [ Test
Step 10 - Throttle Body ]

No

Go to Test Step 11 => [ Test
Step 11 - PCM ]

Test Step 10 - Throttle Body

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the throttle body and the PCM.

Look for any chafed, pierced, pinched, or partially broken wires.

Look for broken, bent, pushed out or corroded terminals.

Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.

Look for the data to change or for the DTC to reset during the wiggle test.

Refer to any technical service bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

No

Replace the throttle body.Disconnect the battery prior to replacing the throttle body. With the scan tool, perform the ETC relearn function after replacement.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

Test Step 11 - PCM

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the throttle body and the PCM.

Look for any chafed, pierced, pinched, or partially broken wires.

Look for broken, bent, pushed out or corroded terminals.

Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.

Look for the data to change or for the DTC to reset during the wiggle test.

Refer to any technical service bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test

No

Replace and program the PCM.

Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test