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.
  Fig 1: Identifying Fuses On E-Box In Engine Compartment, Left Side

  Courtesy of AUDI OF AMERICA, LLC
• 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:

-- 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