CODE P0121, TP SENSOR RANGE/PERFORMANCE PROBLEM "S" & "T" SERIES 4.3L (VIN W) Chevrolet Chevy Van G3500

CODE P0121, TP SENSOR RANGE/PERFORMANCE PROBLEM "S" & "T" SERIES 4.3L (VIN W)

Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .6 volt at idle to about 4.8 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by control module for fuel control and for most other control module control outputs.

Note. Test numbers refer to numbers on diagnostic chart.

1. TP sensor has a self-zeroing feature. If voltage is about .2-.9 volt, control module will use that value at closed throttle. If reading is out or range at idle, check for binding throttle linkage.
2. With TP sensor unplugged, voltage should go low if control module and wiring are okay.

Tech 1 displays throttle position in volts. Voltage should increase steadily as throttle is moved toward WOT.

1. Poor Connection Or Damaged Harness Inspect control module harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
2. Intermittent Test Monitor TP sensor voltage display on Tech 1 while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating location of malfunction.
3. TP Sensor Scaling Observe TP sensor voltage display while depressing accelerator pedal with engine stopped and ignition on. Display should vary from closed throttle TP sensor voltage when throttle is closed (less than 1.25 volts) to greater than 4.5 volts when throttle is held at WOT position.

Code P0121 Schematic ("S" & "T" Series 4.3L - VIN W) Throttle Position Sensor Range/Performance Problem. Scheme 152

Code P0121 Flow Chart ("S" & "T" Series 4.3L - VIN W) Throttle Position Sensor Range/Performance Problem. Scheme 153