P0122

P0122 Throttle Position Sensor Low Voltage




Circuit Description
The powertrain control module (PCM)/engine control module (ECM) supplies a 5 volt reference signal and a ground to the Throttle Position (TP) sensor. The TP sensor sends a voltage signal back to the PCM/ECM relative to the throttle plate opening. The voltage signal will vary from approximately 0.45 volt at closed throttle, to over 4.5 volts at wide open throttle (WOT).

Conditions for Setting the DTC
- TP sensor is less than 0.14 volts.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM/ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history Diagnostic Trouble Code (DTC) is stored.
- The TP angle will default to 0% when the vehicle speed is less than 2 mph (3 kph) and 10% when the vehicle speed is greater than 2 mph (3 kph). (The scan tool will display the defaulted value.)

Conditions for Clearing the MIL/DTC
- The MIL will turn off after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
If a DTC P0122 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the
scan tool DTC information data to determine the status of the DTC. If the DTC occurs intermittently, using the DTC P0121 Diagnostic table may help isolate the problem.

Step 1 - 11:

Step 12 - 13:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. The TP sensor has an auto zeroing feature. If the voltage reading is between 0.2 to 0.9 volts, the PCM/ECM will assume the TP sensor is at a closed throttle position (0%).
5. Simulates a high voltage signal which will identify an open in the signal circuit.
6. If additional DTCs are set, check the 5 V reference circuits for a short to ground.
8. If the test light illuminates while probing the TP signal circuit, then the TP signal circuit is shorted to ground.
11. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.
13. If no faults have been found at this point and no additional DTCs were set, refer to "Diagnostic Aids" for additional checks and information.