Component Tests and General Diagnostics

CAN Bus to ABS Control Module, Checking

Observe all safety precautions: => [ Safety Precautions ] Safety Precautions

View clean working conditions: => [ Clean Working Conditions ] Clean Working Conditions

Prior to repair work, perform a preliminary check to verify the condition. Refer to => [ Preliminary Check ] Preliminary Check.

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, testers and auxiliary items required

• Multimeter

• Wiring diagram

Test requirement

• A CAN bus malfunction was recognized

• The module that does not communicate has ALL power and grounds present at the module connector. Refer to the Wiring Diagrams for pin locations.

• Battery voltage at least 12.5 volts

• All electrical consumers switched off

• Vehicles with automatic transmission, shift selector lever in park or neutral

• A/C switched off

• Ground connections between engine/transmission/chassis OK

• Ignition switched Off

Test procedure

• The engine control module must remain connected for the following step.

- Disconnect the Antilock Brake System (J104) electrical connector.

- Using a multimeter, measure the resistance between the CAN bus low and CAN bus high at the Antilock Brake System (J104) harness connector (with ALL other modules connected). Refer to Wiring Diagrams for Pin locations.

For Vehicles Without Electronic Stabilization Program (ESP):






For Vehicles With Electronic Stabilization Program (ESP):






Specified value: 50 to 69 ohms (at approx. 20° C)

If the specified value was not obtained:

Checking wiring

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to the service information for removal and installation procedures.

- Using a multimeter, measure the resistance of the CAN bus low and CAN bus high circuits. Refer to Wiring Diagrams for location.

Specified value: 1.5 ohms Max.

If the specification was not obtained:

- Check the wires for a short circuit to each other, a short to battery voltage, and a short to ground.

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

- Repair as necessary.

If no malfunction is found in the wiring:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to the service information for removal and installation procedures.

Final procedures

After 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 ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.