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.
Lin-Bus Circuit, Checking: Notes
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
Test requirement
- A LIN Bus malfunction was recognized.
- The Motronic Engine Control Module (ECM) - J623- fuses OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position "P" or "N".
- A/C switched off.
- Ground (GND) connections between engine/transmission/chassis OK.
- Ignition switched off.
Function
The Engine Control Module (ECM) is connected to the Radiator Identification Sensor -G611- module by one LIN data Bus wire. Radiator I.D. and a temperature signal are sent on the LIN bus to the ECM. If the information from the RIS module was not sent or cannot be read, the ECM will store a fault code.
Test procedure
-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK
Start diagnosis
-- Disconnect the Radiator Identification Sensor - G611- electrical harness connector.
-- Turn the ignition switch ON.
-- Using a Multimeter, connect the red Multimeter lead to terminal 3 of the Radiator Identification Sensor -G611- sensor connector and the black lead to engine ground.
Specified value: Battery voltage.
-- Switch the ignition off.
If the specified value was Not obtained:
-- Check the wiring connection for damage, corrosion, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
-- Check for an open or grounded circuit between terminal 3 and fuse SB15.
-- Repair the circuit and replace any open fuses.
-- Go to Final procedures
If the specified value was obtained:
The Motronic Engine Control Module (ECM) - J623- must remain connected for the following step.
-- Connect the Multimeter black lead to terminal 1 and the Multimeter red lead to terminal 3 of the Radiator Identification Sensor -G611- harness connector.
-- Turn the ignition switch ON.
Specified value: Battery voltage.
-- Switch the ignition off.
-- Continue test according to the following table:
| Value | Cause | Test |
|---|---|---|
| If the specified value was not obtained: | Open or shorted circuit | CHECKING WIRING |
| If the specified value was obtained: | Check reference signal circuit | CHECKING WIRING |
NO RELATED
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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.