P0121

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

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

Throttle Position (TP) System:

CIRCUIT DESCRIPTION

The Throttle Position (TP) sensor has a potentiometer whose resistance changes along with the throttle valve position. The Engine Control Module (ECM) provides a 5 volt reference voltage to the TP sensor. The ECM reads the voltage across the TP sensor and converts it into throttle position. When the TP sensor resistance decreases, the throttle valve opening is increasing to wide open throttle, and the voltage being monitored at the ECM increases. When the TP sensor resistance increases, the throttle valve opening is decreasing to idle, and the voltage being monitored at the ECM decreases.


CONDITIONS FOR RUNNING THE DTC

- Engine speed is less than 3500 RPM.

- Maximum flow rate - Minimum flow rate greater than or equal to 25.5 g/s.

- Engine running with Manifold Absolute Pressure (MAP) sensor less than 26 kPa and throttle valve opening less than 35°.

- Engine running with MAP sensor greater than 67 kPa and throttle valve opening greater than 35°.


CONDITIONS FOR SETTING THE DTC


- Difference between expected TP sensor and actual input is greater than a specified value.

- The above conditions are met for at least 3 seconds.

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 ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.


CONDITIONS FOR CLEARING THE MIL/DTC

- The MIL will turn "OFF" after three consecutively passing cycles without a fault present.

- A History DTC will clear after 40 consecutive warm-up cycles without a fault.

- DTC(s) can be cleared by using a scan tool or by disconnecting the ECM battery feed.


DIAGNOSTIC AIDS


Check the following conditions:

- If DTC P0122 or P0123 are also set, refer to either DTC first. P0122
P0123

- Poor connection at ECM. Inspect harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

- Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the TP display on the scan tool while moving connectors and wiring harnesses related to the TP sensor. A change in the TP display will indicate the location of the fault.

- A mis-adjusted TP sensor or a binding or stuck throttle plate could cause the malfunction to set. Refer to TP sensor for adjustment procedures.

If DTC P0121 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.


If any wiring repairs need to be made, Refer to Repair Procedures in Diagrams.

TEST DESCRIPTION

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

1. The Engine OBD System Check prompts the technician to complete some basic checks and store the freeze frame 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.

6. Vehicle must be at operating temperature and a feeler gauge of the specified size must be used.

8. Refer to TP sensor for adjustment procedures.