P0123
DTC P0123 Throttle Position (TP) Sensor Circuit High 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 over 4.65 V at wide open throttle.
Conditions for Running the DTC
- There are no active manifold absolute pressure (MAP) DTCs
- The engine is running.
- The MAP is less than 60 kPa.
- The engine speed is less than 1500 RPM.
Or
- There are no active MAP DTCs
- The engine is running.
- The MAP is more than 60 kPa.
- The engine speed is more than 1500 RPM.
Conditions for Setting the DTC
The TP sensor voltage is more than 3.9 volts for 13.75 seconds when the engine speed is less than 1500 RPM.
Or
TP sensor voltage is more than 4.8 volts when the engine speed is more than 1500 RPM.
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 P0123 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, use the DTC P0105 Diagnostic table in order to isolate the problem.
With the ignition ON and the throttle at the closed position, the voltage should read between 0.20 - 0.90 volts and increase steadily to more than 4.5 volts at wide open throttle.
Steps 1 - 2:
Steps 3 - 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. With the throttle closed, the TP sensor voltage should read less than 0.80 volts. If the TP sensor voltage does not read less than 0.80 volts, check for a binding or a sticking throttle cable.
4. The PCM and the wiring are OK if the TP sensor voltage is less than 0.3 volts with the TP sensor electrical connector disconnected.
5. Probing the ground circuit with a test lamp checks the circuit for high resistance which will cause a DTC P0123 to set.
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 volt reference circuit to ground or battery voltage, the others volt reference circuits will also have a low or high voltage.
7. A shorted 5 volt reference circuit will also set additional DTCs.
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.