Throttle Position Sensor: Testing and Inspection

DIAGNOSTIC CODES: P 0121, P 0122, P 0123





Monitoring Procedure
The range is checked for values outside the limits.

When faults are present a default value of throttle position will be supplied which will be one of two values using estimated manifold pressure. High manifold pressure will cause the default to be a high value of throttle position which will indicate full load, otherwise the default will be a mid-range value of throttle position. While fault counting is in progress a back-up value of throttle position will be supplied which will be the last valid value.

The strategy will report to the Diagnostic Status Manager (DSM) when all the tests have been performed once; the DSM will then decide whether to store a fault code and illuminate the MIL Lamp.

Fig. 2 TPS Circuit:

TP Circuit Range/Performance, Diagnostic Code P 0121
Possible causes:
- Engine unable to breathe properly - blocked inlet or exhaust system
- TP harness / connector partial short circuit or open circuit - undetected by range checks
- ECM stepper position is wrong but undetected
- TP faulty
- MAFS signal is wrong but undetected
- IAT sensor is wrong but undetected
- Extreme altitude barometric conditions and limit components have been encountered
- ECM engine speed value is wrong

TP Position Circuit Low Input, Diagnostic Code P 0122
A range check on the output of the throttle position sensor is performed to check for input values outside expected limits.
- High voltage threshold: 4.0 V
- Low voltage threshold: 0.15 V

High voltage test not performed at engine loads greater than 0.36 g/s. High voltage test counter not incremented until all conditions for test failure have been present for longer than 5 seconds.

Possible causes:
- Partial short circuit to ground or open circuit in TP signal wire/connectors
- TP supply low - wiring/connectors high resistance
- TP faulty low out of range
- ECM fault in Analogue to Digital Conversion (ADC) and interface circuit - gives low volts

TP Circuit High Input, Diagnostic Code P 0123
A range check on the output of the throttle position sensor is performed to check for input values outside expected limits.
- High voltage threshold: 4.0 V
- Low voltage threshold: 0.15 V

High voltage test not performed at engine loads greater than 0.36 g/s. High voltage test counter not incremented until all conditions for test failure have been present for greater than 5 seconds.

Possible causes:
- TP ground harness/connectors open circuit
- TP faulty high out of range
- ECM load signal is wrong (too low) but undetected
- ECM fault in Analogue to Digital Conversion (ADC) and interface circuit gives high volts