ECM Power Source Circuit: Procedure

Fig 1: Identifying E78 & B49 ECM Connectors

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Turn the ignition switch to ON.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   E78-22 (+B) - B49-12 (E1)	Ignition switch ON	11 to 14 V

   TEXT IN ILLUSTRATION
   
   

   *1	Component with harness connected (ECM)

NG → See step   2 

OK → See step   8 

Fig 2: Identifying B49 ECM Connector

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Standard Resistance (Check for Open)

   Tester Connection	Condition	Specified Condition
   B49-12 (E1) - Body ground	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Rear view of wire harness connector (to ECM)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

Fig 3: Identifying (E77 & B49 IGSW Voltage) Connector Terminals

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1. Turn the ignition switch to ON.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   E77-21 (IGSW) - B49-12 (E1)	Ignition switch ON	11 to 14 V

   TEXT IN ILLUSTRATION
   
   

   *1	Component with harness connected (ECM)

NG → See step   7 

OK: Go to next step 

Fig 4: Identifying E78 & B49 ECM (MREL Voltage) Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Turn the ignition switch to ON.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   E78-9 (MREL) - B49-12 (E1)	Ignition switch ON	11 to 14 V

   TEXT IN ILLUSTRATION
   
   

   *1	Component with harness connected (ECM)

NG → See step   10 

OK: Go to next step 

Fig 5: Identifying EFI Relay

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Remove the EFI relay from the engine room relay block.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   3 - 5	Battery voltage not applied	10 kΩ or higher
   	Battery voltage applied to terminals 1 and 2	Below 1 Ω

NG → REPLACE EFI RELAY 

OK: Go to next step 

1. Remove the EFI relay from the engine room relay block.
2. Disconnect the ECM connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance (Check for Open)

   Tester Connection	Condition	Specified Condition
   1 (EFI relay) - E78-9 (MREL)	Always	Below 1 Ω
   2 (EFI relay) - Body ground	Always	Below 1 Ω

   Standard Resistance (Check for Short)

   Tester Connection	Condition	Specified Condition
   1 (EFI relay) or E78-9 (MREL) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → CHECK AND REPAIR HARNESS OR CONNECTOR (TERMINAL +B OF ECM - BATTERY POSITIVE TERMINAL) 

Fig 6: Measuring Resistance Of Ignition Switch Assembly With Ohmmeter

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   All Terminals	LOCK	10 kΩ or higher
   2-3	ACC	Below 1 Ω
   2-3-4, 6-7	ON	Below 1 Ω
   1-2-4, 6-7-8	START	Below 1 Ω

NG → See step   9 

OK → CHECK AND REPLACE HARNESS OR CONNECTOR (BATTERY - IGNITION SWITCH, IGNITION SWITCH - ECM)