P1121

DTC P1121

Circuit Description

The throttle position (TP) sensor is used by the powertrain control module (PCM) in order to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. Rotation of the TP sensor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts through the TP sensor signal circuit. If the PCM detects an intermittent, excessively-high signal voltage, this DTC will set.


DTC Descriptor

This diagnostic procedure supports the following DTC. DTC P1121 Throttle Position (TP) Sensor Circuit Intermittent High Voltage


Conditions for Running the DTC

- The ignition is ON.

- DTCs P0641 and P0651 are not set.

- DTC P1121 runs continuously once the above conditions are met.


Conditions for Setting the DTC

- The TP sensor voltage is more than 4.8 volts.

- The intermittent condition exists for more than 1 second during a 2 second period.


Action Taken When the DTC Sets

- The control module stores the DTC information into memory when the diagnostic runs and fails.

- The malfunction indicator lamp (MIL L) will not illuminate

- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

- The driver information center, if equipped, may display a message.


Conditions for Clearing the DTC

- A current DTC Last Test Failed clears when the diagnostic runs and passes.

- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

- Clear the DTC with a scan tool.


Diagnostic Aids

Electromagnetic interference (EMI) can cause an intermittent DTC. Inspect the related circuits for being too close to the secondary ignition wires and to the generator.

If the engine has sat overnight, the engine coolant temperature (ECT) and the intake air temperature (IAT) values should display within a few degrees of each other. If the temperatures are not within 3°C (5°F). For an intermittent condition, refer to Intermittent Conditions.Symptom Related Diagnostic Procedures


Test Description

DTC P1121 Steps 1-6:

DTC P1121 Steps 7-10:

The number below refers to the step number on the diagnostic table.

7. This test will determine an intermittent faulty TP sensor utilizing the DMMs MIN MAX, 100 millisecond capture mode.