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
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 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:
- 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 .