Can-Bus Instrument Cluster To Data Bus OBD Interface, Checking

Observe all safety precautions: SAFETY PRECAUTIONS 

View clean working conditions: CLEAN WORKING CONDITIONS 

Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.

For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.

Special tools and workshop equipment required 

• Multimeter
• Wiring diagram

Test requirement 

• A CAN-Bus malfunction was recognized.
• The Engine Control Module (ECM) - J623- fuses OK.
• 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) -J623- communicates with other CAN-Bus capable control modules.

The control modules are connected by two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange information (messages). Missing information on the CAN-bus is recognized as a malfunction by the Engine Control Module (ECM) -J623- and the other control modules connected to the CAN-bus.

Trouble-free operation of the CAN-Bus requires that it have a terminal resistance. This central terminal resistance is located in the Engine Control Module (ECM) -J623-.

Test procedure 

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

Start diagnosis 

-- Disconnect the Instrument Cluster Control Module -J285- electrical harness connector.

-- Using a multimeter, check the Instrument Cluster Control Module -J285- electrical harness connector terminals T32/29 to T32/30 for resistance.

Specified value: 60 to 72 Ω (at approx. 20° C)

If the specified value was not obtained: 

-- Check the wiring for a short circuit to Battery (+), or an open circuit.

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

-- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring: 

-- Replace the Engine Control Module (ECM) -J623-.

If the specified value was obtained: 

Checking wiring 

-- Remove the Engine Control Module (ECM) -J623-.

-- Using a multimeter, check the Data Bus On Board Diagnostic Interface -J533- electrical harness connector to the Instrument Cluster Control Module -J285- electrical harness connector T32 for resistance.

Instrument Cluster Control Module -J285- electrical harness connector T32 terminals	Data Bus On Board Diagnostic Interface -J533- electrical connector T20 terminals
29	18
30	8

Specified value: 1.5 Ω Max.

If the specified value was not obtained: 

-- Check the wiring for a short circuit to Battery (+), or an open circuit.

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

-- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring: 

-- Replace the Instrument Cluster Control Module -J285-.

Final procedures 

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 .