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.
Testing if display approx. 140.0°C
-- Disconnect the Engine Coolant Temperature (ECT) Sensor (on radiator) -G83- electrical harness connector -1-.
If indication jumps to approx. -40.0° C:
-- Switch ignition off.
-- Replace the Engine Coolant Temperature (ECT) Sensor (on radiator) - G83-.
If indication remains at approx. 140.0° C:
Checking wiring
If the manufacturers test box is being used. Perform the following step.
-- Install the test box.
If the manufacturers test box is not being used. Perform the following step.
-- Remove the Motronic Engine Control Module (ECM) -J623-.
-- Using a multimeter, check the Engine Coolant Temperature (ECT) Sensor (on radiator) - G83- electrical harness connector terminals to the Motronic Engine Control Module (ECM) -J623- electrical harness connector T94 terminals for an open circuit according to the wiring diagram.
| Engine Coolant Temperature (ECT) Sensor (on radiator) - G83- electrical harness connector terminals | Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminals or test box socket |
|---|---|
| 1 | 26 |
| 2 | 12 |
Specified value: 1.5 Ω Max.
If the specification was not obtained:
-- Check the wiring for high resistance, an open or a short to voltage or ground.
-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
-- Perform a road test to verify repair.
If the DTC does not return:
Generate readiness code. Refer to READINESS CODE .
If the DTC does return, no malfunction is detected in the wiring and the voltage supply is OK:
-- Replace the Motronic Engine Control Module (ECM) -J623-.
-- Assembly is performed in the reverse of the removal.
-- If ECT Sensor G62, Engine Coolant Temperature (ECT) Sensor (on radiator) G83 and Motronic Engine Control Module (ECM) J623 have no malfunctions, inspect Coolant Fans V7 & V177; Coolant Fan Control Modules J293 & J671. If resistance and voltage checks are not acceptable, repair as required
-- If resistance and voltage checks are satisfactory, replace affected Coolant Fan & Control Module (serviced as an assembly).
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
- Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
- If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
- If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .
Use the Manual With the Right Hardware
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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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