Standard Emissions

CODE 21 THROTTLE POSITION SENSOR (TPS) CIRCUIT

TPS Circuit Diagnostic Chart:

TP Sensor Circuit:

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 5.0 volt reference to the sensor. The ECM reads the voltage across the sensor and converts it into throttle position. When the sensor resistance decreases, indicating the throttle valve opening is increasing to wide open throttle, the voltage being monitored at the ECM increases. When the sensor resistances increases, indicating the throttle valve opening is decreasing to idle, the voltage being monitored as the ECM decreases.

Diagnostic Trouble Code (DTC) 21 will set if the following condition is met for at least 2 seconds; High voltage input at the ECM indicated with the engine running at idle.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for an open or short to B+ in LT GRN/WHT wire or for a faulty ECM.
2. Checks for an open or short to B+ in LT GRN wire or for a faulty ECM.
3. Checks for a faulty ECM or a misadjusted or faulty TP sensor.

DIAGNOSTIC AIDS
For TP sensor adjustment procedure, refer to Throttle Position Sensor / Adjustments.

DTCs 21 and 22 stored at the same time could be the result of an open LT GRN wire.