How to Troubleshoot a Corvette Throttle Position Sensorby Lee Sallings
The throttle position sensor (TPS) in your Corvette is a variable resistor that changes resistance as the throttle is opened and closed. When the sensor develops a fault, some or all of the positions of the sensor will act as open circuits, causing a drop-out in the signal voltage to the on-board computer. When the computer senses the loss of signal voltage, while the other sensors that it uses for engine load calculations indicate a load on the engine, it will store a diagnostic trouble code and turn on the "Check Engine" light on the dash.
Locate the sensor on the side of the throttle body near the front of the engine. Insert a straight pin into the electrical connector, alongside the dark blue wire in the center of the connector, until it contacts the terminal inside the connector.
Clip the red (Positive) meter lead to the straight pin and the black (Negative) meter lead to engine ground (a bolt or other metal part on the engine). Turn the ignition key to "Run" but do not start the engine.
Open the throttle slowly, by moving the throttle cable with your hand, while watching for a drop-out in voltage. The voltage should rise smoothly from less than 2 volts (Throttle Closed) to 4.5 volts (Throttle Open). If the voltage suddenly drops to zero and then comes back, replace the sensor. This is a dynamic test, and it isolates the TPS from other things that could be causing the malfunction.
Items you will need
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