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.
1988 Jeep WagoneerFACTORY OEM SERVICE PROCEDURE
Mat Sensor Test
- Disconnect wire harness connector from MAT sensor. 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 specified range. See TEMPERATURE-TO-RESISTANCE VALUES 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 is greater than one ohm is indicated.
TEMPERATURE-TO-RESISTANCE VALUES (CTS & MAT SENSOR)
| °F | °C (Approximate) | Ohms |
|---|---|---|
| 212 | 100 | 185 |
| 160 | 70 | 450 |
| 100 | 38 | 1600 |
| 70 | 20 | 3400 |
| 40 | 4 | 7500 |
| 20 | -7 | 13,500 |
| 0 | -18 | 25,000 |
| -40 | -40 | 100,700 |
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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