Skylark L4-144 2.4L DOHC VIN T SFI (1997)
Throttle Position Sensor: Description and Operation
TP Sensor Service
Description
Notice: Numbers in text correspond to numbered components in image.
The Throttle Position (TP) sensor (2) is a potentiometer connected to the throttle shaft on the throttle body. The TP sensor electrical circuit consists of a
5 volt supply line and a ground line, both provided by the Powertrain Control Module (PCM), and a signal line to the PCM. By monitoring the voltage
on this signal line, the PCM can calculate throttle position angle in a percentage.
Operation
As the throttle valve angle is changed (accelerator pedal moved), the output of the TP sensor also changes. At a closed throttle position, the output of the
TP sensor is low (approximately 0.6 volt). As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be
near 5 volts. The PCM can determine fuel delivery based on throttle valve angle (driver demand).
Circuit Faults
A broken or loose TP sensor can cause intermittent bursts of fuel from the injectors and an unstable idle, because the PCM thinks the throttle is moving.
A high or low voltage problem in the TP sensor circuits should set either a DTC P0122 or DTC P0123. The PCM also has the capability of setting a
DTC P0121 if the sensor is reading out of range. Once a diagnostic trouble code is set, the PCM will use a default value for the TP sensor, and some
vehicle performance will return.
