Sunfire L4-138 2.3L DOHC VIN D MFI (1995)
Throttle Position Sensor: Description and Operation
Throttle Position Sensor
DESCRIPTION
The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal
line, the PCM calculates throttle position. As the throttle valve angle is changed (accelerator pedal moved), the TP sensor signal also changes. At a
closed throttle position, the output of the TP sensor is low. As the throttle valve opens, the output increases so that at Wide Open Throttle (WOT),
the output voltage should be above 4 volts.
OPERATION
The PCM calculates fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor may cause intermittent bursts of fuel
from an injector and unstable idle because the PCM thinks the throttle is moving. A hard failure in the TP sensor 5 volts reference or signal
circuits should set either a DTC P0122 or DTC P0123. A hard failure with the TP sensor ground circuit may set DTCs P0123 and P0117. Once a
DTC is set, the PCM will use an artificial default value based on engine RPM and mass air flow for throttle position and some vehicle performance
will return. A high idle may result when either DTC P0122 or DTC P0123 is set.
