DCM Local Can

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

Trouble causes:

DCM local CAN communication circuit is shorted to ground.
DCM local CAN communication circuit is shorted to power supply.
DCM local CAN communication circuit is shorted between lines.
DCM failure
airbag control module failure

Wiring diagram:

CAN communication system Ref. to WIRING SYSTEM>CAN COMMUNICATION SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to LAN SYSTEM (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION

NOTE:

When measuring the resistance of CAN communication circuit, measure it in sleep status.
To enter sleep status
- With ignition switch OFF and key or switch operation stopped, keep the doors and trunk all closed for one minute or more.
- On model with the keyless access with push button start, keep the access key 2 m or more away from the vehicle.

CHECK BASIC DIAGNOSTIC PROCEDURE .
Check that the basic diagnosis has been performed up to STEP 3.

NOTE:
Possible defective parts can be narrowed easily by inspection using Subaru Select Monitor before performing "CHECK CAN COMMUNICATION CIRCUIT" using a tester.

Was the basic diagnostic procedure performed?

Yes : Go to 2.

No : Perform the basic diagnostic procedure. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE
CHECK FOR SHORT TO GROUND IN DCM LOCAL CAN COMMUNICATION CIRCUIT .
1. Turn the ignition switch to OFF.
2. Disconnect the DCM connector.
3. Disconnect the airbag control module connector.
4. Using a tester, measure the resistance between DCM connector and chassis ground.
  Connector & terminal
  
  (i105) No. 6 - Chassis ground:
  
  (i105) No. 16 - Chassis ground:
Is the resistance less than 10 Ω?

Yes : Repair or replace the short circuit to ground in harness between DCM connector and airbag control module connector.

No : Go to 3.
CHECK FOR SHORT TO POWER SUPPLY IN DCM LOCAL CAN COMMUNICATION CIRCUIT .
1. Turn the ignition switch to ON.
2. Using a tester, measure the voltage between DCM connector and chassis ground.
  Connector & terminal
  
  (i105) No. 6 (+) - Chassis ground (-):
  
  (i105) No. 16 (+) - Chassis ground (-):
Is the voltage 5 V or less?

Yes : Go to 4.

No : Repair or replace the short circuit to power supply in harness between DCM connector and airbag control module connector.
CHECK FOR SHORT CIRCUIT BETWEEN LINES IN DCM LOCAL CAN COMMUNICATION CIRCUIT .
1. Turn the ignition switch to OFF.
2. Using the tester, measure the resistance between terminals.
  Connector & terminal
  
  (i105) No. 6 - (i105) No. 16:
Is the resistance 1 MΩ or more?

Yes : Go to 5.

No : Repair or replace the short circuit between the harness lines between DCM connector and airbag control module connector.
CHECK END RESISTANCE .
1. Connect the DCM connector.
2. Using a tester, measure the resistance between terminals in airbag control module connector.
  CAUTION:
  To measure the voltage and resistance of airbag system component, be sure to use the specified test harness. Ref. to AIRBAG (DIAGNOSTICS)>GENERAL DESCRIPTION
  
  Connector & terminal
  
  (AB42) No. 42 - (AB42) No. 43:
Is the resistance 114 - 126 Ω?

Yes : Go to 6.

No : Replace the DCM. Ref. to ENTERTAINMENT & MONITORING>DATA COMMUNICATION MODULE
CHECK END RESISTANCE .
1. Disconnect the DCM connector.
2. Connect the airbag control module connector.
3. Using a tester, measure the resistance between terminals in DCM connector.
  Connector & terminal
  
  (i105) No. 6 - (i105) No. 16:
Is the resistance 114 - 126 Ω?

Yes : CAN communication circuit is normal.

No : Replace the airbag control module. Ref. to AIRBAG SYSTEM>airbag control module