Can Bus To Abs Control Module, Checking

Observe all safety precautions: SAFETY PRECAUTIONS 

View clean working conditions: CLEAN WORKING CONDITIONS 

Prior to repair work, perform a preliminary check to verify the condition. Refer to PRELIMINARY CHECK .

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

See Appropriate Wiring Diagram Information for component locations and connector views.

Special Tools And Workshop Equipment 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 Appropriate 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 

-- 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 Appropriate Wiring Diagrams for Pin locations.

For Vehicles Without Electronic Stabilization Program (ESP): 

Antilock Brake System -J104- electrical harness T26 connector terminals	Motronic Engine Control Module (ECM) electrical harness connector T94 terminals
21 CAN Lo	67
23 CAN Hi	68

For Vehicles With Electronic Stabilization Program (ESP): 

Antilock Brake System -J104- electrical harness T26 connector terminals	Motronic Engine Control Module (ECM) electrical harness connector T94 terminals
13 CAN Lo	67
12 CAN Hi	68

Specified Value: 50 To 69 Ω (At Approx. 20° C) 

If the specified value was not obtained:

Checking wiring

-- Remove the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate 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 Appropriate Wiring Diagrams for location.

Specified Value: 1.5 Ω 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 appropriate 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 .
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 .