DTC B2278: Engine Switch Circuit Malfunction: Procedure

1. Use the Data List to check if the engine switch is functioning properly.
   MAIN BODY
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Start Switch1	Start switch 1/ON or OFF	ON: Engine switch on (IG) OFF: Engine switch off	-
   Start Switch2	Start switch 2/ON or OFF	ON: Engine switch on (IG) OFF: Engine switch off	-

   OK

   When the engine switch is turned on (IG), ON is displayed on the Techstream.

NG → See step   4 

OK: Go to next step 

1. Clear the DTCs, refer to DTC CHECK / CLEAR .
2. Turn the engine switch on (IG), and check whether DTC B2278 is output.
   RESULT
   
   

   Result	Proceed to
   No DTC output	A
   DTC B2278 output	B

B → REPLACE MAIN BODY ECU 

A → See step   3 

Fig 1: Identifying Engine Switch Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the E18 engine switch connector.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   7 (SS1) - 5 (GND)	Pushed	Below 1 Ω
   2 (SS2) - 5 (GND)	Pushed	Below 1 Ω
   7 (SS1) - 5 (GND)	Not pushed	10 kΩ or higher
   2 (SS2) - 5 (GND)	Not pushed	10 kΩ or higher

NG → See step   6 

OK: Go to next step 

Fig 2: Identifying Engine Switch And Main Body ECU Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the E1 main body ECU connector.
2. Disconnect the E18 engine switch connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   E1-17 (SSW1) - E18-7 (SS1)	Always	Below 1 Ω
   E1-16 (SSW2) - E18-2 (SS2)	Always	Below 1 Ω
   E18-5 (GND) - Body ground	Always	Below 1 Ω
   E1-17 (SSW1) or E18-7 (SS1) - Body ground	Always	10 kΩ or higher
   E1-16 (SSW2) or E18-2 (SS2) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → REPLACE MAIN BODY ECU