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.
1989 Jeep WagoneerFACTORY OEM SERVICE PROCEDURE
Manifold Air Temperature (Mat) Sensor
- Disconnect wire harness connector from MAT sensor. Using an ohmmeter, check sensor resistance.
- With engine at operating temperature, resistance should be less than 1000 ohms. See TEMPERATURE SENSOR RESISTANCE VALUES table. If resistance is not within specification, replace MAT sensor.
- Using an ohmmeter, check resistance between ECU wire harness pin No. 32 and MAT sensor connector terminal. See Figure . Also, check resistance between ECU wire harness pin No. 14 and MAT sensor connector terminal. If resistance is greater than one ohm, repair wire harness as required.
Factory Service Tools
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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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