Throttle Position Sensor (TPS)

1. The TPS is mounted on the side of the throttle body, opposite the throttle lever. Test sensor by backprobing sensor connector with a DVOM.
2. Ensure there is continuity between TPS terminal "B" (ground circuit) and chassis ground. See Fig 1 . With ignition on, ensure there is a 5-volt reference signal at terminal "A" of the sensor connector.
3. With throttle closed, measure TPS SIGNAL voltage at terminal "C". If voltage is greater than 1.25 volts with ignition on and throttle closed, replace sensor. Hold throttle at Wide Open Throttle (WOT) and measure voltage. If WOT voltage is not approximately 4.5 volts, replace sensor.
4. Voltage should range from 1.25 or less at closed throttle to 4.25 at WOT. The ECM has the ability to auto-zero a voltage reading of less than 1.25 volts. This means a reading of less than 1.25 volts will be determined by the ECM to be 0% throttle angle opening.
5. A Scan tester may be used to check TPS voltage. Some Scan testers translate the voltage signal to a percent (%) reading. A voltage reading of 1.25 volts or less may be translated to a 0% throttle opening.

Fig 1: Throttle Position Sensor Circuit

Courtesy of GENERAL MOTORS CORP.