Lin-Bus Circuit, Checking

Special tools and workshop equipment required

multimeter.
Wiring diagram.

Test requirement

A LIN Bus malfunction was recognized.
The Motronic Engine Control Module (ECM) - J220- fuses OK.

Fig 1: 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 via the LIN data Bus 3 wire connector. 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- module connector and the black lead to ground.

Fig 2: 3-Pin Electrical Harness Connector

Courtesy of AUDI OF AMERICA, LLC

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) -J220- connector terminal 52.

Checking wiring

-- Disconnect the Motronic Engine Control Module (ECM) -J220- 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) -J220- 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 Ω 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- (with radiator assembly).

Final procedures

After the repair work, the following work steps must be performed in the following 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 .