K 2500 Suburban 4WD V8-5.7L VIN R (1999)
Throttle Position Sensor: Description and Operation
Throttle Position Sensor-3
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
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 volt.
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. A problem in the TP sensor 5 volt 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.
