DTC B2278: Engine Switch Circuit Malfunction: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Check the Data List of proper functioning of the start switch.

   HINT: 

   When using the Techstream with the engine switch off, turn on and off any of the door courtesy light switches repeatedly at 1.5 second intervals or less until communication between the Techstream and vehicle starts.

   POWER SOURCE CONTROL
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Start Switch1	Start Switch 1 / ON or OFF	ON: Engine switch is pushed OFF: Engine switch is not pushed	-
   Start Switch2	Start Switch 2 / ON or OFF	ON: Engine switch is pushed OFF: Engine switch is not pushed	-

   OK

   ON (engine switch is pushed) and OFF (engine switch is not pushed) appear on the screen.

NG → See step   3 

OK: Go to next step 

1. Clear the DTC. Refer to DTC CHECK / CLEAR .
2. Turn the engine switch on (IG).
3. Check for DTC.

   OK

   DTC B2278 is not output.

NG → REPLACE POWER SOURCE CONTROL ECU 

OK → See step   5 

1. Remove the engine switch. Refer to REMOVAL .
   Fig 1: Identifying Engine Switch Connector Terminal

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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

   HINT: 

   This engine switch is momentary type switch.

NG → See step   6 

OK: Go to next step 

1. Disconnect the J55 connector from the power source control ECU.
   Fig 2: J55 Connector Terminal

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	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 (POWER SOURCE CONTROL ECU - ENGINE SWITCH) 

OK → REPLACE POWER SOURCE CONTROL ECU