Lin-Bus Circuit, Checking: Overview

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 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.

-- Switch the ignition 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.

-- Switch the ignition off.

If the specified value was Not obtained:

-- Check for an open or grounded circuit between terminal 3 and fuse SB15 in Fuse Panel B.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

-- Repair the circuit and replace any open fuses.

-- Go to Final procedures

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 voltage.

-- Switch the ignition On.

Specified value: Battery voltage.

-- Switch the ignition off.

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.

-- Check the wiring connection for damage, corrosion, loose or broken terminals.

-- If necessary, repair the faulty wiring connection, if no faults were found with the wiring or connections. Replace the Motronic Engine Control Module (ECM) - J623 -. Refer to appropriate service information.

-- Go to Final procedures

If the specified value was obtained:

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.

-- 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.

Radiator Identification Sensor - G611- electrical harness connector terminal	Motronic Engine Control Module (ECM) electrical harness connector T94 terminal or test box socket
2	64

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.

-- Go to Final procedures

If the specified value was obtained:

-- Replace the Radiator Identification Sensor - G611- (with radiator assembly).

Final procedures 

-- Reinstall the engine cover with air filter, if necessary. Refer to the appropriate service information.

-- 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 .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .