Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGEO1993PRIZM L4-1600CC 1.6L DOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTHROTTLE POSITION SENSORDESCRIPTION AND OPERATION
1993 Geo Prizm L4-1600cc 1.6L DOHC
Throttle Position Sensor: Description and Operation
1993 Geo Prizm L4-1600cc 1.6L DOHCSECTION Description and Operation
Throttle Position Sensor (TPS) Operation:
The Throttle Position Sensor (TPS) is a potentiometer that is mounted to the throttle body.
The TPS is a three wire sensor with a referance voltage, a ground provided by the ECM, and a sensor output signal to the ECM. The sensor output signal is a DC voltage that varies with throttle angle.
The ECM supplies a five-volt signal to the sensor through a resistor in the ECM and measures the signal voltage. As the throttle angle is changed (accelerator pedal moved), the output of the sensor also changes. At closed throttle, the out put voltage is low. As throttle angle increases, the output increases so that, at wide open throttle, the output approaches 5 volts.
By monitoring the output voltage of the TPS, the ECM can modify fuel delivery based on throttle angle.
The TPS also houses an idle switch. The ECM supplies both ignition voltage and a ground to the idle switch. When the throttle is closed, the ECM senses the voltage drop caused by the switch closed to ground. The ECM uses this information as a reference for idle air control operation.
A failure in the TPS sensor circuit should set a Diagnostic Trouble Code (DTC) 41.
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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.