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 Test
- Disconnect wire harness connector from MAT sensor. See Fig 1 . Test resistance of sensor with a high impedance digital ohmmeter. Resistance should be less than 1000 ohms with engine warm. Replace sensor if resistance is not within range and temperature specified. See TEMPERATURE & RESISTANCE VALUES (CTS & MAT SENSOR) table.
- Test resistance of wire harness between ECU wire harness connector terminal D-3 and sensor connector terminal. Repeat test with terminal C-8 at ECU and sensor connector terminal. Repair wire harness if an open circuit or resistance of greater than one ohm is indicated.
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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