Taillight Relay Circuit: Procedure

WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

PERFORM ACTIVE TEST USING TECHSTREAM

Connect the Techstream to the DLC3.
Turn the ignition switch on (IG).
Turn the Techstream on.
Enter the following menus: Body Electrical / Body / Active Test.

Check the operation.

BODY (BODY ECU)

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

Tail lights come on.

NG → See step 2

OK → PROCEED TO PROBLEM SYMPTOMS TABLE NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

INSPECT RELAY

Inspect TAIL relay continuity.

Fig 1: Identifying Tail Relay Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Remove the tail relay from the instrument panel J/B.

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

Standard resistance

Tester Connection	Specified Condition
3 - 5	10 kΩ or higher
3 - 5	Below 1 Ω (When battery voltage is applied to terminal 1- 2)
3 - 4	Below 1 Ω (When battery voltage is applied to terminal 1- 2)

NG → REPLACE RELAY

OK: Go to next step

CHECK HARNESS AND CONNECTOR (BATTERY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

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

Fig 2: Identifying 1A Instrument Panel Junction Block Assembly Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard voltage

Tester Connection	Condition	Specified Condition
IA-1 - Body ground	Always	10 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step

INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

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

Fig 3: Identifying Instrument Panel Junction Block Assembly Connector Terminals

Standard voltage

Tester Connection	Condition	Specified Condition
IC-4 - Body ground	Light control switch OFF → TAIL	Below 1 V → 10 to 14 V
IC-5 - Body ground	Light control switch OFF → TAIL	Below 1 V → 10 to 14 V
ID-6 - Body ground	Light control switch OFF → TAIL	Below 1 V → 10 to 14 V
ID-14 - Body ground	Light control switch OFF → TAIL	Below 1 V → 10 to 14 V
IP-8 - Body ground	Light control switch OFF → TAIL	Below 1 V → 10 to 14 V

NG → PROCEED TO PROBLEM SYMPTOMS TABLE NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

OK → REPAIR OR REPLACE HARNESS OR CONNECTOR (EACH TAILLIGHT CIRCUIT)