Throttle Position Sensor: Testing and Inspection

1995 Chevrolet S10/T10 P/U 2WD L4-2.2L VIN 4SECTION Testing and Inspection
When a Diagnostic Trouble Code (DTC) is set, the Powertrain Control Module (PCM) will use an artificial value for throttle position and some engine performance will return.

A broken Throttle Position (TP) sensor can cause intermittent bursts of fuel from the injector(s) and an unstable idle because the PCM thinks the throttle is moving.

A scan tool reads throttle position in volts and should read from 0.45-0.85 volt with the throttle closed, ignition "ON" or at idle. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT).

Scan TP signal while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from below 0.85 volt (850 mV) when throttle was closed, to over 4.5 volts (4500 mV) when throttle is held at wide open throttle position.

TP SENSOR OUTPUT
This check should be performed when TP sensor attaching parts have been replaced. A Tech 1 can be used to read the TP signal output voltage, or:

1. Connect digital voltmeter J 39200 or equivalent, from TP sensor connector terminal "B" (BLK wire) to terminal "C" (DK BLU wire). Jumpers for terminal access can be made using terminals "1214836" and "12014837".

2. With ignition "ON," engine stopped, the TP sensor voltage should be less than 0.85 volt if more than 0.85 volt verify free throttle movement. If still more than 1.25 volts, replace TP sensor.

3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.