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 Mercedes Benz 560SLFACTORY OEM SERVICE PROCEDURE
Code 3, Coolant Temperature Sensor
- Turn ignition to "OFF" position. Unplug CIS-E control unit connector. Check resistance between sockets No. 7 and No. 21. Resistance reading should be as indicated in table. See Fig 1 . If not okay, check wiring.
- Unplug coolant temperature sensor connector. Measure resistance between any 2 of the diagonally opposed terminals and compare resistance values from each internal sensor. Resistance reading should be as indicated in table. See Fig 1 . If not okay, replace sensor.
- Check wiring harness continuity to CIS-E control unit. Resistance should be less than one ohm. If not okay, check for open circuit.
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.