CAN resistor and communication line inspection

■ Inspection procedure for impedance measurement

When measuring impedance, it is generally necessary to disconnect the circuit being tested from the power supply before hand. The vehicle's battery should therefore be disconnected and wait about four minutes to allow all capacitors in the system to discharge.

Inspection procedure for resistance test:

The CAN bus must be disconnected from the power supply.
The measurement is taken between the CAN High and CAN Low leads.
The measurement recorded may differ from the specified levels by a few ohms.

■ Impedance measurement with matching resistor

Ignition "OFF" and disconnect the battery and wait about four minutes.
Make sure all modules are properly connected.
Measure resistance between C-CAN Low and C-CAN High terminal of Data Link Connector (DLC).
Specification: Approx. 60 Ω
Is the measured resistance within specification?
YES
- Check each module connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "VERIFICATION OF VEHICLE REPAIR " procedure.
NO
- If the measured value is out of specification, go to "CAN resistor inspection" procedure below.
  * If the measured value is approx. 0Ω, then check for short CAN communication line.
  
  * If the measured value is approx. 120Ω, then check for open CAN communication line of control module with resistor.

■ CAN resistor inspection

Ignition "OFF.
Disconnect ECM/PCM and Instrument Cluster connectors.
Measure resistance between C-CAN Low and C-CAN High terminal of each ECM/PCM and Instrument Cluster Modules.
Specification: About 120 Ω
Is the measured value within specification?
YES
- Go to "CAN COMMUNICATION LINE INSPECTION " procedure.
NO
- If the measured value is out of specification, repair or replace 120Ω CAN register (Inside of ECM/PCM and Instrument Cluster) and then, go to "CAN COMMUNICATION LINE INSPECTION " procedure.