DTC B278A: Short to GND in Immobilizer System Power Source Circuit: Procedure

WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

CHECK WIRE HARNESS (CERTIFICATION ECU - ENGINE SWITCH)

Disconnect the D39 ECU connector.

Fig 1: Identifying D39 Certification ECU Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Disconnect the D21 switch connector.

Fig 2: Identifying D21 Engine Switch Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Measure the resistance according to the value(s) in the table below.

Resistance

Tester Connection	Condition	Specified Condition
D39-30 (VC5) - D21-14 (VC5)	Always	Below 1 Ω
D39-40 (AGND) - D21-8 (AGND)	Always	Below 1 Ω
D39-30 (VC5) - Body ground	Always	10 kΩ or higher
D39-40 (AGND) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step

REPLACE ENGINE SWITCH (RECONFIRM DTC)
1. Replace the engine switch.
2. Clear the DTC and repeat the procedure to re-check it. Refer to DTC CHECK / CLEAR .
  OK
  
  DTC is not output.
OK → END (ENGINE SWITCH IS DEFECTIVE)

NG → REPLACE CERTIFICATION ECU