P0122

DTC P0122 Throttle Position Sensor Low Voltage




Circuit Description
The 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 ECM relative to the throttle plate opening. The voltage signal will vary from approximately 0.1 volts at closed throttle, to over 4.9 volts at wide open throttle (WOT).

Conditions for Setting the DTC
- Ignition ON.
- TP sensor is less than 0.14 V.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The 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 DTC is stored.
- The Coolant fan turns on.
- The TP angle will default to 0% when the vehicle speed is less than 2 mph (3 kmph) and 10% when the vehicle speed is greater than 2 mph (3 kmph). (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.
- The DTC(s) can be cleared 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 information data to determine the status of the DTC. If the DTC occurs intermittently, using the Diagnostic table may help isolate the problem.

Steps 1 - 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 ECM will assume the TP sensor is at a closed throttle position (0%).
4. Simulates a high voltage signal which will identify an open in the signal circuit.
5. If additional DTCs are set, check the 5 volt reference circuits for a short to ground.
6. If the test light illuminates while probing the TP signal circuit, then the TP signal circuit is shorted to ground.
8. The replacement ECM must be reprogrammed. Refer to Powertrain Control Module / Service and Repair.
11. If no faults have been found at this point and no additional DTCs were set, refer to "Diagnostic Aids" for additional checks and information.