P0123

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The Throttle Position (TP) sensor contains a potentiometer whose resistance value changes along with the throttle valve position. The Powertrain Control Module (PCM) provides a 5 volt reference voltage to the TP sensor. The PCM reads the voltage across the TP sensor and converts it into the throttle position. The TP sensor resistance decreases as the throttle valve opening increases. When the TP sensor resistance decreases the voltage being monitored at the PCM will increase. And when the TP sensor resistance increases, because the throttle valve opening is decreasing, the voltage being monitored at the PCM will decrease.

Conditions for Setting the DTC

^ High voltage input at the PCM indicated with the engine running (greater than 96%).

^ Above condition is met for at least 0.5 seconds.

Action Taken When the DTC Sets

^ The Malfunction Indicator Lamp (MIL) will illuminate.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

^ The PCM will enter the Fail-Safe Function and assume the throttle position is 20° while stopping Idle Speed (ISC) control.

Conditions for Clearing the MIL/DTC

^ The MIL will turn OFF after three consecutively passing cycles without a fault present.

^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.

^ DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

Diagnostic Aids

Check for any of the following conditions:

^ A misadjusted TP sensor or a binding or stuck throttle plate could cause the malfunction to set. Refer to Throttle Position Sensor / Adjustments for TP sensor adjustment procedures.

^ Before replacement of the TP sensor check the resistance of the TP sensor, between terminals 1 and 4 - 2.87 to 5.33k ohms, and terminals 1 and 3 - 100 to 20k ohms. Replace the TP sensor if not within these values.

^ When a DTC P0108, P0113, P0118 and P0123 are set together the cause could be an open ground circuit (LT. GRN/BLK wire).

^ A poor connection at the PCM. Inspect the harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal to wire connection.

^ A damaged wiring harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the TP display on the scan tool while moving connectors and wiring harnesses related to the TP sensor. A change in the TP display will indicate the location of the fault.

If a DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

If any wiring repairs need to be made, Refer to Repair Procedures in Electrical Diagrams.

Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Observing the TP sensor parameter from closed throttle position to wide open throttle the percentage of the TP sensor movement should not be greater than 96%.

11. The TP sensor adjustment must be checked and set to specifications. Replace the TP sensor if proper adjustment cannot be made. Refer to Throttle Position Sensor for TP sensor adjustment and replacement procedures.