P0121

Throttle Position (TP) Sensor Circuit:

Circuit Description
The Powertrain Control Module (PCM) supplies a 5V reference signal and a ground to the sensor. The Throttle Position (TP) sensor sends a voltage signal back to the PCM relative to throttle blade opening. Voltage will vary from 0.45V at closed throttle to over 4.5V at wide open throttle.

Conditions For Setting The DTC
- The Map sensor reads less than 37 kPa.
- The TP sensor is stable ± 2%.
- One or more of the following DTCs are not set P0107, P0108, P0122.
- Whenever the TP angle is greater than one of the following specified percentage at the given RPM.
- 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 after 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.

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.
- DTCs can be cleared by using a scan tool.

Diagnostic Aids
Whenever a DTC P0121 cannot be duplicated, use the information included in the "Freeze Frame". The Data can be used to determine the conditions when the DTC set.

DTC P0121 - Throttle Position (TP) System Performance (1 Of 2):

DTC P0121 - Throttle Position (TP) System Performance (2 Of 2):

Test Description
Numbers below refer to the Step numbers on the Diagnostic Table.
1. The OBD System Check prompts the Technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
2. The TP sensor has an auto zeroing feature. Whenever the voltage reading is between 0.2 to 0.9 volts, the PCM will assume that the TP sensor is at a closed throttle position. Whenever the reading is out of the auto zeroing range at closed throttle look for a binding or damaged linkage.
11. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Replacement PCM must be reprogrammed.