Powertrain Control Module (PCM)

P0123-TPS/APP CIRCUIT HIGH

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The three wire Throttle Position Sensor (TPS) provides the PCM with an input signal voltage that represents the throttle blade position of the throttle body. The TPS is connected to the throttle blade shaft. As the position of the throttle blade changes, the output voltage of the TPS changes.

The PCM supplies approximately 5.0 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. This will vary in an approximate range from 0.26 volts at minimum throttle opening (idle), to 4.49 volts at maximum opening or wide open throttle.

The Accelerator Pedal Position Sensor (APPS) is a linear potentiometer. The APPS provides the PCM with a voltage signal proportional to the angle or position of the accelerator pedal. The APPS signal along with inputs from other sensors is used by the PCM to calculate the throttle plate position.

- When Monitored:
Continuously with the ignition on and engine running.

- Set Condition:
This DTC will set if the monitored TPS voltage rises above 4.94 volts for 0.48 of a second.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DETERMINING IF RELATED ENGINE TPS/APPS DTCS ARE PRESENT
1. With the scan tool, check Engine DTCs, this includes all one trip failures.

Are any Engine TPS/APPS DTCs present?

Yes

- Testing and Inspection and perform the appropriate diagnostic procedure.

No

- Go To 2

2. CHECK IF THE DTC IS CURRENT
1. With the scan tool, record the Event Data to help identify the conditions in which the DTC set.
2. With the scan tool, erase PCM DTCs and the Event Data.

NOTE: Clearing DTCs does NOT erase the Event Data. To erase the Event Data you must perform a Quick Learn procedure or battery disconnect (if available) with the scan tool, or manually disconnect the battery. Whatever method used might reset certain learned transmission values to controller defaults and may cause poor shift quality until those values are relearned.

3. Using the Event Data recorded earlier, test drive the vehicle while trying to duplicate the operating conditions in which the DTC set.
4. With the scan tool, read DTCs.

Did this DTC reset during the road test?

Yes

- Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM. With the scan tool, perform a Quick Learn. Powertrain Control Module - Removal.
- Perform the 65RFE TRANSMISSION VERIFICATION TEST. 65RFE Transmission Verification Test.

No

- Go To 3

3. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle the wiring and connectors while checking for shorted and open circuits.
4. With the scan tool, check the Event Data to help identify the conditions in which the DTC set.

Were any problems found?

Yes

- Repair as necessary.
- Perform the 65RFE TRANSMISSION VERIFICATION TEST. 65RFE Transmission Verification Test.

No

- Test Complete.