CAN-BUS TERMINAL RESISTANCE Instrument Cluster Control Module -J285- TO Data Bus On Board Diagnostic Interface -J533-, CHECKING

WARNING: This page is about a different car, the 2014 Audi A8 Quattro and 2013 Audi A8. However, it is still accessible from the selected car via links, so may be relevant.

The Engine Control Module -J623- communicates with all data-bus capable control modules via a CAN databus.

These databus capable control modules are connected via two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange information (messages). Missing information on the databus is recognized as a malfunction and stored.

Trouble-free operation of the CAN-bus requires that it have a terminal resistance. The central terminal resistor is located in the Engine Control Module -J623-.

Special tools and workshop equipment required

Multimeter.
Wiring Diagram

Test requirement

A CAN-Bus malfunction was recognized.
The Engine Control Module -J623- fuses OK.
Battery voltage at least 12.5 V.
Ignition switched off.

Test Procedure

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

-- Disconnect the Instrument Cluster Control Module -J285- harness connector T32 from the Instrument Cluster Control Module.

NOTE:

The Engine Control Module -J623- must remain connected for the following step.

-- Disconnect the Data Bus On Board Diagnostic Interface -J533- harness connector T32b from the diagnostic interface.

-- Using a Multimeter, check continuity between J285 and J533.

Specified value: max. 1.5Ω (at approx. 20°C).

Instrument Cluster Control Module -J285- harness connector terminals	Data Bus On Board Diagnostic Interface -J533- harness connector T32b terminals.
T32 / 4 (Can_Bus High)	T32b / 22
T32 / 3 (Can_Bus Low)	T32b / 6

If the specified value was Not obtained:

-- Check the wiring connection for an open circuit, short circuit to Battery voltage or Ground (GND).

-- 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 Engine Control Module -J623-. Refer to Repair information.

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 .