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Home >> Subaru >> 2018 >> BRZ Premium >> Repair and Diagnosis >> Electrical >> Starter >> Entry Start System Start System (Keyless Start) >> Entry & Start System (Start Function) >> DTC U0073: Control Module Communication Bus "A" Off; DTC U0100: Lost Communication With ECM/PCM "A"; DTC U0101: Lost Communication With TCM; DTC U0122: Lost Communication With Vehicle Dynamics Control Module; DTC U0140: Lost Communication With Body Control Module; DTC U0155: Lost Communication With Instrument Panel Cluster (IPC) Control Module; DTC U0401: Invalid Data Received From ECM/PCM "A"; DTC U0422: Invalid Data Received From Body Control Module >> Circuit description
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Circuit description

These DTCs are output when a CAN communication error is found between the collation ECM (smart key ECM ASSY) and the ECM, the main body ECM, the combination meter ASSY, or the engine stop and start ECM.

NOTE: After removing the cable, if you reconnect it to the battery ground terminal (-), the power mode returns to the same status it was before you removed the cable.
DTC No. DTC detection status Faulty part DTC Output Confirmation Operation
U0073 Problem in the CAN communication system (1 trip detection) CAN communication system Turn the ignition switch to ON and wait 10 seconds or more.
U0100 CAN communication problem between the collation ECM (smart key ECM ASSY) and the ECM (1-trip detection logic*) ECM Turn the ignition switch to ON and wait 10 seconds or more.
U0101 CAN communication problem between the collation ECM (smart key ECM ASSY) and the TCM (1-trip detection logic*) TCM Turn the ignition switch to ON and wait 10 seconds or more.
U0122 CAN communication problem between the collation ECM (smart key ECM ASSY) and the brake actuator ASSY (1-trip detection logic*) Brake actuator ASSY Turn the ignition switch to ON and wait 10 seconds or more.
U0140 CAN communication problem between the collation ECM (smart key ECM ASSY) and the main body ECM (multiplex network body ECM) (1-trip detection logic*) Main body ECM (multiplex network body ECM) Turn the ignition switch to ON and wait 10 seconds or more.
U0155 CAN communication problem between the collation ECM (smart key ECM ASSY) and the combination meter ASSY (1-trip detection logic(1)) Combination meter ASSY Turn the ignition switch to ON and wait 10 seconds or more.
U0401 CAN communication problem between the collation ECM (smart key ECM ASSY) and the ECM (1-trip detection logic*) ECM Turn the ignition switch to ON and wait 10 seconds or more.
U0422 CAN communication problem between the collation ECM (smart key ECM ASSY) and the main body ECM (multiplex network body ECM) (1-trip detection logic*) Main body ECM (multiplex network body ECM) Turn the ignition switch to ON and wait 10 seconds or more.
(1) The code is output only when the problem is found and the engine switch is on (IG).
VEHICLE STATUS AND FAILSAFE FUNCTION WHEN PROBLEM DETECTED

DTC code Vehicle status when a problem is detected Failsafe function when a problem is detected
U0073 No effect on the vehicle status. -
U0100 No effect on the vehicle status. If the following conditions are met, the problem can be determined to be in the CAN communication, not the direct line (TACH).
  • If you press the engine switch and the system controls the engine based on the engine speed sent via the direct line, the engine stops cranking.
  • If you press the engine switch and the system controls the engine based on the engine speed sent via the direct line, the engine stops cranking.

If the following conditions are met, the problem can be determined to be in both the CAN communication and the direct line (TACH).
  • After you press the engine switch, the engine cranking stops after 6 seconds.
  • While pressing the engine switch, 30 seconds pass and the engine is still cranking.
U0101 No effect on the vehicle status. -
U0122 No effect on the vehicle behavior. -
U0140 The doors can no longer be locked or unlocked. The warning (wireless buzzer) does not sound. -
U0155 The warning (meter buzzer) does not sound, and the meter does not issue a warning. -
U0401 No effect on the vehicle status. -
U0422 The doors can no longer be locked or unlocked. The warning (wireless buzzer) does not sound. -
DIAGNOSTIC CODES DESCRIPTION - RELATED (DATA MONITOR) AND (ACTIVE TEST)

Diagnostic codes [Data monitor] item [Active Test] item
U0073
U0100
U0101
U0122
U0140
U0155
U0401
U0422		 - -
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