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 2015 Audi A7 Quattro and 2014 Audi A7 Quattro. 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 .