Express 1/2 Ton Van V8-305 5.0L VIN M SFI (1998)
Throttle Position Sensor: Description and Operation
Throttle Position (TP) Sensor
DESCRIPTION
The Throttle Position (TP) sensor is a potentiometer. The TP sensor is connected to the throttle shaft on the throttle body. By monitoring the
voltage on the signal line, the VCM 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 4.0 volts.
PURPOSE
The VCM 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 VCM thinks the throttle is moving.
DIAGNOSIS
A problem in the TP sensor 5V reference or signal circuits should set either a DTC P0122 or DTC P0123. A problem with the TP sensor ground
circuit may set DTCs P0123 and P0117. Once a DTC is set, the VCM will use an artificial default value based on mass air flow for TP sensor and
some vehicle performance will return. A high idle may result when either DTC P0122 or DTC P0123 is set.
