CAN Bus Terminal Resistance, Checking

CAN Bus Terminal Resistance, 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.

• 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 (ECM) must remain connected for the following step:

- Disconnect the Module that was no response, or the CAN Bus wires can be accessed at the Data Bus On Board Diagnostic Interface (J533)

- Using a multimeter, measure the resistance between the CAN bus low and CAN bus high in the disconnected Module electrical connector. Refer to Wiring Diagrams for location.

Specified value: 58 to 72 ohms (at approx. 20° C)

If the specified value was obtained:

- Check for power and ground present to the module that does not communicate. If the power and grounds are present to the Module, but the Module does not communicate, replace the Module that did not communicate on the Bus. Refer to the Repair Information for removal and installation procedures.

If the specified value was not obtained:

Checking wiring

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

- Using a multimeter, measure the resistance of the CAN Bus High circuit between the disconnected Module on the Bus and ECM. Repeat the procedure for the CAN Bus Low. Refer to Wiring Diagrams for pin locations.

Specified value: 1.5 ohms Max.

If the specification was Not obtained:

- Check the wires for a short circuit, high resistance, or an open.

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

- Repair as necessary.

If no malfunction is found in the wiring and the Bus resistance was Not obtained:

- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.

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.