DTC U145B: Invalid Data Received From Restraints Control Module Local Bus

Diagnosis start condition: 

When ignition switch is ON.

DTC detecting condition: 

• Defective airbag.
• Defective DCM.

Trouble symptom: 

• Impossible to send AACN data.
• RED LED illuminates.

Wiring diagram: 

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

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Read the DTC of [Telematics] using the Subaru Select Monitor. Ref. to TELEMATICS SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U145B displayed? (Current code)

   Yes:  Go to  2.

   No:  Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
2. REMOVE OR INSTALL VEHICLE BATTERY TERMINAL  .
   1. Turn the ignition switch to ON.
   2. Disconnect the ground terminal from battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
   3. After five seconds, connect the ground terminal to battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
   4. Turn the ignition switch to ON.
   5. Read the DTC of [Telematics] using the Subaru Select Monitor. Ref. to TELEMATICS SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U145B displayed? (Current code)

   Yes:  Go to  3.

   No:  Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
3. CHECK DCM (INTERNAL RESISTANCE)  .
   1. Turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the ground terminal from the battery sensor. REPAIR CONTENTS>NOTE>BATTERY .
   2. Disconnect the airbag CM connector.
   3. Connect the connector (1BF) in the test harness BF to the airbag CM connector.
   4. Using a tester, measure the resistance between connectors in test harness BF. (Measure the internal resistance of DCM from the test harness 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 

   1. (8BF) No. 1 - (8BF) No. 2: (internal resistance of DCM)

   Is the resistance 114 - 126 Ω?

   Yes:  Go to  4.

   No:  Replace the DCM. Ref. to ENTERTAINMENT & MONITORING>DATA COMMUNICATION MODULE .

4. 1. Disconnect the DCM connector (i105).
   2. Connect the airbag CM connector.
   3. Using a tester, measure the resistance between DCM connectors. (Measure the internal resistance of airbag CM from DCM connectors)

   Connector & terminal 

   1. (i105) No. 6 - (i105) No. 16: (internal resistance of airbag CM)

   Is the resistance 114 - 126 Ω?

   Yes:  Go to  5.

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

5. CHECK DCM  .
   1. Restore the vehicle to its original state.
   2. Turn the ignition switch to ON.
   3. Using the Subaru Select Monitor, perform the clear memory of [Telematics]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY .
   4. Turn the ignition switch to OFF.
   5. Turn the ignition switch to ON.
   6. Wait for 1 minute.
   7. Read the DTC of [Telematics] using the Subaru Select Monitor. Ref. to TELEMATICS SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U145B displayed? (Current code)

   Yes:  Replace the DCM. Ref. to ENTERTAINMENT & MONITORING>DATA COMMUNICATION MODULE .

   No:  Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.