Taillight Relay Circuit: Procedure

1. Connect Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn Techstream on.
4. Select the following menu items: Body Electrical / Main Body / Active Test.
5. Check that the relay operates.
   MAIN BODY:
   
   

   Tester Display	Test Part	Control Range	Diagnostic Note
   Taillight Relay	Taillight relay	ON/OFF	-

   OK

   Taillight relay operates. (Taillights illuminate.)

NG → See step   2 

OK → See step   6 

1. Remove the TAIL fuse from the instrument panel junction block.
2. Measure the resistance according to the value(s) in the table below.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   TAIL fuse	Always	Below 1 Ω

NG → REPLACE FUSE 

OK: Go to next step 

1. Remove the taillight relay from the instrument panel junction block.
   Fig 1: Inspecting Taillight Relay

   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
   3 - 5	Voltage is not applied between terminals 1 and 2	10 kΩ or higher
   	Apply the battery voltage between terminals 1 and 2	Below 1 Ω
   3 - 4	Voltage is not applied between terminals 1 and 2	Below 1 Ω
   	Apply the battery voltage between terminals 1 and 2	10 kΩ or higher

NG → REPLACE TAILLIGHT RELAY 

OK: Go to next step 

1. Measure the voltage between the loading slot of the TAIL fuse and body ground.
   Fig 2: Identifying TAIL Fuse Terminal

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard voltage

   Tester Connection	Condition	Specified Condition
   TAIL fuse terminal - Body ground	Light control switch OFF → TAIL	Below 1 V → 11 to 14 V

NG → See step   5 

OK → REPAIR OR REPLACE HARNESS OR CONNECTOR (FUSE - BODY GROUND) 

1. Disconnect the 1A instrument panel junction block connector.
   Fig 3: Checking Harness And Connector (Battery - Instrument Panel Junction Block)

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

   Standard voltage

   Tester Connection	Condition	Specified Condition
   1A-1 - Body ground	Always	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → REPLACE MAIN BODY ECU (INSTRUMENT PANEL JUNCTION BLOCK)