P0123

DTC P0123

Circuit Description

The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit, a common low reference circuit, and 2 independent signal circuits.

The TP sensors have opposite functionality. The TP sensor 1 signal voltage increases from below 1 volt at idle to above 4 volts at wide open throttle (WOT). The TP sensor 2 signal voltage decreases from above 4 volts at idle to below 1 volt at WOT.

If the ECM detects TP sensor 1 signal voltage is too high, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0123 Throttle Position (TP) Sensor 1 Circuit High Voltage

Conditions for Running the DTC

* The ignition is ON, with the engine OFF or the engine is operating.
* The ignition 1 voltage is more than 7 volts.
* DTC P0123 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects the TP sensor 1 signal voltage is more than 4.6 volts for more than 4 seconds.

Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
* Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

* Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
* The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views.
* If there is a condition with the TP sensors the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected.
* For an intermittent condition, refer to Intermittent Conditions. Intermittent Conditions

Test Description

Step 1 - Step 8:

Step 9 - Step 18:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that a condition exists.
5. This step tests the signal circuit for a short to voltage. If the scan tool displays a voltage after the TP sensor is disconnected, the circuit is shorted to a voltage.
7. This step tests for high resistance in the low reference circuit of the TP sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to power down completely.
8. This step tests the low reference circuit for a short to voltage.