DTC B2278: Engine Switch Circuit Malfunction: Procedure

1. Check that the connectors are securely connected and the terminals are not deformed or loose.

   OK

   The connectors are securely connected and the terminals are not deformed or loose.

NG → REPAIR OR REPLACE CONNECTORS 

OK: Go to next step 

1. Disconnect the J55 ECU connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Standard resistance

   Tester Connection (Symbols)	Condition	Specified Condition
   J55-6 (GND2) - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the engine switch.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Standard resistance

   Tester Connection (Symbols)	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

   HINT: 

   This switch is a momentary type switch.

NG → REPLACE ENGINE SWITCH 

OK: Go to next step 

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

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard resistance

   Tester Connection (Symbols)	Condition	Specified Condition
   J31-7 (SS1) - J55-14 (SSW1)	Always	Below 1 Ω
   J31-2 (SS2) - J55-37 (SSW2)	Always	Below 1 Ω
   J31-5 (GND) - Body ground	Always	Below 1 Ω
   J31-7 (SS1) or J55-14 (SSW1) - Body ground	Always	10 kΩ or higher
   J31-2 (SS2) or J55-37 (SSW2) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Reconnect the connectors.
2. Connect Techstream to the DLC3.
3. Turn the engine switch on (IG).
4. Check the DATA LIST for proper functioning of the start switches 1 and 2.
   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 Swtich2	Start Switch 2/ ON or OFF	ON: Engine switch on (IG) OFF: Engine switch OFF	-

   OK

   ON (engine switch on (IG)) and OFF (engine switch off) appear on the screen.

NG → REPLACE POWER SOURCE CONTROL ECU 

OK: Go to next step 

1. Delete the DTCs. Refer to DTC CHECK / CLEAR [08/2012 - ] .
2. Check for DTCs again.

   OK

   DTC B2278 is not output.

NG → REPLACE POWER SOURCE CONTROL ECU 

OK → CHECK INTERMITTENT PROBLEMS