Front Fog Light Circuit
The main body ECU (multiplex network body ECU) controls the front fog lights.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
- Inspect the fuses for circuits related to this system before performing the following inspection procedure.
- If the main body ECU (multiplex network body ECU) is replaced, refer to Registration (See page
).*1 - *1: w/ Smart Key System
PERFORM ACTIVE TEST USING TECHSTREAM (FRONT FOG LIGHT RELAY)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Body Electrical / Main Body / Active Test.
(e) Perform the Active Test according to the display on the Techstream.
Main BodyTester Display | Test Part | Control Range | Diagnostic Note |
|---|---|---|---|
Front Fog Light Relay |
Front Fog Light |
ON/OFF |
- |
OK:
Front fog lights illuminate.
| OK | ![]() |
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE |
|
INSPECT FOG FR RELAY
(a) Remove the FOG FR relay from the engine room relay block. |
![]() |
(b) 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 to terminals 1 and 2 |
10 kΩ or higher |
3 - 5 |
Battery voltage applied to terminals 1 and 2 |
Below 1 Ω |
| NG | ![]() |
REPLACE FOG FR RELAY |
|
CHECK HARNESS AND CONNECTOR (BATTERY - FOG FR RELAY)
(a) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection | Condition | Specified Condition |
|---|---|---|
Relay terminal 1 - Body ground |
Always |
11 to 14 V |
Relay terminal 3 - Body ground |
Always |
11 to 14 V |
| NG | ![]() |
REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
CHECK HARNESS AND CONNECTOR (FOG FR RELAY - DRIVER SIDE JUNCTION BLOCK)
(a) Disconnect the 1F driver side junction block connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection | Condition | Specified Condition |
|---|---|---|
Relay terminal 2 - 1F-27 |
Always |
Below 1 Ω |
1F-27 - Body ground |
Always |
10 kΩ or higher |
| NG | ![]() |
REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
INSPECT DRIVER SIDE JUNCTION BLOCK
(a) Remove the driver side junction block. |
![]() |
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection | Condition | Specified Condition |
|---|---|---|
1F-27 - MB-7 (FFOG) |
Always |
Below 1 Ω |
1F-27 - Body ground |
Always |
10 kΩ or higher |
*a |
Component without harness connected (Driver Side Junction Block) |
| OK | ![]() |
REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) |
| NG | ![]() |
REPLACE DRIVER SIDE JUNCTION BLOCK |
Test yourself
A quick Toyota Tacoma quiz: every answer comes with an explanation and a link to the manual page.
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