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
Coolant Temperature Sensor (Cts)
- Disconnect wire harness connector from CTS. Using an ohmmeter, test resistance between sensor terminals.
- With engine at operating temperature, resistance should be less than 1000 ohms. See TEMPERATURE SENSOR RESISTANCE VALUES table below. Replace sensor if resistance is not within specification.
- Using an ohmmeter, Check for continuity between ECU wire connector pin No. 15 and CTS connector terminal. Also, check resistance between pin No. 32 and CTS connector terminal. See Fig 1 . Repair wire harness if an open is indicated.
TEMPERATURE SENSOR RESISTANCE VALUES
| °F (°C) | (1) Ohms | ||
|---|---|---|---|
| 212 (100) | 85 | ||
| 160 (70) | 450 | ||
| 100 (38) | 1600 | ||
| 70 (20) | 3400 | ||
| 40 (4) | 7500 | ||
| 20 (-7) | 13,500 | ||
| 0 (-18) | 25,000 | ||
| -40 (-40) | 100,700 | ||
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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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