1988 Jeep WagoneerFACTORY OEM SERVICE PROCEDURE

Throttle Position Sensor (TPS)

  1. Turn ignition on. Check throttle position sensor input voltage. Connect voltmeter negative lead to terminal "B" (M/T), or terminal "D" (A/T) of sensor connector. Connect voltmeter positive lead to terminal "A" (M/T and A/T) of sensor connector.
    NOTE: On (A/T) models, connector terminals are identified by letters molded into back of connector. On all models, do not disconnect TPS harness connector. Insert voltmeter test leads through back of wire harness connector. On some models, it may be necessary to remove throttle body from intake manifold to gain access to sensor wire harness.
  2. Move and close throttle plate completely (M/T and A/T). Ensure throttle linkage contacts stop. Note voltmeter reading. Input voltage at terminals "B" and "A" (M/T), or terminals "A" and "D" (A/T) should be 5 volts.
  3. Return throttle plate to closed throttle position (M/T and A/T). Check sensor output voltage. To do so, disconnect voltmeter positive lead from terminal "A" and connect it to terminal "C" (M/T), or terminal "B" (A/T).
  4. Maintain throttle plate in closed position (M/T and A/T). Ensure throttle linkage contacts stop. Note voltmeter reading. Output voltage should be .8 volt (M/T), or 4.2 volts (A/T).
  5. If output voltage is incorrect, loosen bottom sensor retaining screw and pivot sensor in adjustment slot for a coarse adjustment. Loosen top sensor retaining screw for fine adjustments. Tighten screws after adjustment.
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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.

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