P0121

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The PCM supplies a 5 V reference signal and a ground to the sensor. The Throttle Position (TP) sensor sends a voltage signal back to the PCM relative to the throttle plate opening. Voltage will vary from approximately 0.45 V at closed throttle, to over 4.5 V at wide open throttle (WOT).

CONDITIONS FOR SETTING THE DTC

^ TP is stable ±2 %.

^ MAP is less than 37 kPa.

^ DTC(s) P0107, P0108, P0122 not set.

^ TP angle is greater than the following specified percentages at the given RPM's.

- TP angle is greater than 60 % at 1600 RPM

- TP angle is greater than 77 % at 2400 RPM

- TP angle is greater than 89 % at 3200 RPM

- TP angle is greater than 100 % at 4000 RPM

ACTION TAKEN WHEN THE DTC SETS

^ The Malfunction Indicator Lamp (MIL) will illuminate afier two consecutive ignition cycles in which the diagnostic runs with the fault active.

^ The PCM 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.

^ Coolant tan turns ON.

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 P0121 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.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD 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 fault occurred. The information is then stored in 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 will assume the TP sensor is at a closed throttle position (0%). If the reading is out of the auto zeroing range at closed throttle look for a binding or damaged linkage.

6. In order for DTC P0121 to set with a short voltage in the TP signal circuit, the voltage must be minimal enough to not set a DTC P0123 and more than 0.5 V.

11. Replacement PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.