The throttle position sensor (TPS) is a variable resistor that signals the ECM the degree of throttle opening. Sensor is connected to 5-volt reference and has the highest resistance at closed throttle position. At wide open throttle position, resistance is lowest and output to the ECM will be about 5 volts.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

This step checks for complete 5-volt reference circuit. If circuit is complete from voltage reference and back to sensor ground in ECM, a voltage reading of about 5 volts should be measured.
This step checks for shorted or stuck 4th gear switch. When the transmission shifts into 4th gear, the switch will close and signal the ECM to turn EGR off. If the 4th gear switch is not faulty, there could be a short to voltage reference or a faulty TPS adjustment or sensor.
This step checks for normal response at ECM from TPS. Voltage should normally be less than 1 volt at closed throttle and go to about 5 volts at wide open throttle. If voltage change is okay, circuit is complete.

Fig 1: TPS Check

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.

Safety Warning

TPS Check

Use the Manual With the Right Hardware

When to See a Mechanic

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