Express 1/2 Ton Van V8-305 5.0L VIN M SFI (1998)
Throttle Position Sensor: Testing and Inspection
Throttle Position Sensor (DTCs Set)
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. This may cause an unstable idle because the VCM detects the throttle is moving.
When the VCM detects a malfunction with the TP sensor circuits, the following DTCs will set:
^
DTC P0121 circuit performance malfunction.
^
DTC P0122 circuit low.
^
DTC P0123 circuit high.
^
DTC P1121 intermittent circuit high.
^
DTC P1122 intermittent circuit low.
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.
