LIN-Bus Circuit, Checking

Diagnostic Procedures

LIN-Bus Circuit, Checking

Special tools, testers and auxiliary items 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 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 data 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 ] 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) module connector and the black lead to ground.

Specified value: Battery voltage.

If the specified value was Not obtained:

- Check for an open or grounded circuit between terminal 3 and fuse SB 15.

- Repair the circuit and replace the fuse if blown.

If the specified value was obtained:

- Connect the black multimeter lead to terminal 1 of the Radiator Identification Sensor (G611) harness connector and the red lead to Battery positive.

Specified value: Battery voltage.

If the specified value was Not obtained:

- Check for an open circuit or high resistance between Radiator Identification Sensor (G611) terminal 1 and the Motronic Engine Control Module (ECM) (J623) connector terminal 52.

Checking wiring

- Disconnect the Motronic Engine Control Module (ECM) (J623) T94 electrical harness connector.

- Disconnect the Radiator Identification Sensor ( G611) module T3 electrical harness connector.

- Using a multimeter, check the Motronic Engine Control Module (ECM) (J623) T94 electrical harness connector terminal 64 to the Radiator Identification Sensor (G611) module T3 electrical harness connector terminal 2 for resistance.

Specified value: 1.5 ohms max

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.

If the specified value was obtained:

- Replace the Radiator Identification Sensor (G611 ) (radiator assembly). Refer to the repair information.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Scan Tool Testing and Procedures.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Scan Tool Testing and Procedures.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.