How To Test A Throttle Position Sensor On A Pontiac Fiero

Learning how to test a throttle position sensor on your Pontiac Fiero can help save you a lot of time and money on repairs.  The throttle position sensor is instrumental in helping your Fiero determine the optimum throttle opening for acceleration, idle and fuel economy.  The type of throttle position sensor used is a potentiometer used by the computer to determine the width and rate of the throttle opening.  As time goes on, this part will eventually fall out of calibration or completely fail, requiring testing and recalibration or in severe cases, total replacement. On some model Fieros, the throttle position sensor will be secured by bolts that are welded in place and are consequently non-adjustable.  This means that in the event of a throttle position sensor failure, the entire throttle body has to be replaced. 

What you’ll need:

• Screwdriver
• ¼ inch drive sockets and Torx bits
• Voltmeter

1. Locate the throttle position sensor.  It will be attached to the throttle body near the air hose.  Remove both the air cleaner and air hose to gain access to the throttle body.
2. Test the sensor.  The throttle position sensor will have three wires coming from the connector – a black or orange wire for ground, a blue signal wire and a grey wire that delivers power to the sensor.  Connect one lead of the voltmeter to the blue wire and the other lead to ground.  Turn the ignition to the “on” position and check the voltage.  If the readings show more than 1 volt, adjust the sensor until the readings are at around 0.5 volts.  If there is no signal, connect one lead to the black or orange wire and the other lead to ground.  If the voltage is above 100mV, the throttle position sensor needs replacement.
3. Adjust the sensor.  If the throttle position sensor is secured by removable screws, use the ¼ inch drive ratchet and Torx bit to loosen the two screws on the side of the throttle position sensor.  With the voltmeter attached and key to “on”, rotate the throttle position sensor until the voltage is around 0.5 volts.