P0122
DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage
Circuit Description
The PCM supplies a 5.0 V reference signal and a ground to the throttle position (TP) sensor. The TP sensor sends a voltage signal back to the PCM relative to the throttle plate opening. The voltage will vary from approximately 0.35 V at closed throttle, to more than 4.65 V at wide open throttle.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The TP sensor reads less than 0.20 V for 6.25 seconds.
Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tool's Freeze Frame and Failure Records
Conditions for Clearing the MIL/DTC
- The control module turns OFF the MIL after 3 consecutive drive trips during which the diagnostic test Runs and Passes.
- A history DTC clears after 40 consecutive warm-up cycles during which no fault is detected. A warm up cycle occurs when the engine coolant temperature rises 22° C (40° F) above the startup temperature and exceeds 70° C (158° F) during the same ignition cycle.
- The DTCs can be cleared using the scan tool Clear Information function.
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 in order to determine the status of the DTC. If the DTC occurs intermittently, use the DTC P0105 Diagnostic table in order to isolate the problem.
Steps 1 - 3:
Steps 4 - 6:
Steps 7 - 10:
Steps 11 - 13:
Test Description
The numbers below refers to the step numbers on the Diagnostic Table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
2. The TP sensor has an auto zeroing feature. If the voltage reading is between 0.20 Volts and 0.90 Volts, the PCM will automatically assume this as a closed throttle position (0 percent).
4. This simulates a DTC P0123. If the PCM recognizes the high voltage signal, this indicates that the PCM and the wiring are OK.
5. This simulates a high voltage signal which will identify an open in the signal circuit.
IMPORTANT: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.
6. If any additional DTCs are set, check the 5.0 Volt reference circuits for a short to ground.
8. If the test lamp illuminates while probing the TP signal circuit terminal in step 5, then the TP signal circuit is shorted to ground.
11. Program the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming.