P0123

DTC P0123

CIRCUIT DESCRIPTION
The throttle position (TP) sensor is used by the engine control module (ECM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with the following 3 circuits:
- A 5-volt reference
- A low reference
- A signal

The ECM provides the TP sensor with 5 volts on the 5-volt reference circuit, and a ground on the low reference circuit. The TP sensor provides a signal voltage that changes relative to throttle plate angle. The TP sensor signal voltage at idle is less than 0.5 volt. The TP sensor voltage is typically near 0.0 volts at idle, but could be as high as 0.5 volts. The TP sensor voltage should increase to above 4 volts at wide open throttle (WOT). If the ECM detects an excessively high signal voltage, DTC P0123 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage

CONDITIONS FOR RUNNING THE DTC
- The ignition is ON or the engine is running.
- DTC P0123 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC

IMPORTANT: The scan tool displays a voltage near 0.0 volts. Do not use the scan tool voltage parameter to determine if there is a TP sensor condition.

The ECM detects that the TP sensor signal voltage is more than 4.9 volts for a total of 2.5 seconds during a 5 second time period.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

TEST DESCRIPTION

Step 1:

Steps 2-6:

Steps 7-9:

Steps 10-15:

4. This step determines if there is a short to voltage or an open condition in the circuits.
9. This step determines if the circuit has a short to voltage. A short to voltage can cause multiple DTCs to set.