Inspect/Test/Service

Some throttle position sensors are adjustable. Follow manufacturer's instructions.

• On older engines, correct adjustment is crucial to proper system operation.
• On newer engines, this is not as important because the computer uses whatever reading it takes at idle as base voltage (adaptive learn strategy).

Incorrect TP sensor adjustment may cause:

• Inaccurate idle speed,
• Engine stalling, and
• Acceleration stumbles.

Follow these steps to adjust a typical TP sensor:

• Backprobe the TP sensor signal wire and connect a voltmeter from this wire to ground.
• Turn on the ignition switch and observe the voltmeter reading with the throttle in the idle position.
• If the TP sensor does not provide the specified voltage, loosen the TP sensor mounting bolts and rotate the sensor housing until the specified voltage is indicated on the voltmeter.

A TP Sensor with elongated slots for sensor adjustments. Courtesy of General Motors Corporation - Chevrolet Motor Division.

• Hold the sensor in this position and tighten the mounting bolts to the specified torque.

Most throttle position sensors are made so that their adjustments are tamperproof. They have screws that are either soldered or staked.

To remove the switch, these might need to be drilled or filed off. After the new switch is installed and adjusted, the new mounting screws are restaked.