2012 Fog relay

[CTScott]

Originally Posted by Absolutely Red 12

No DRLs.

Also now using a PIAA switch, as the cheap Chinese Toyota looking switch would not allow the fogs to turn off.

New switch is a 3 wire, internal lighting, when on. It also allows the dash icon to turn on!!

You should use a four, not three wire switch. The illumination should be isolated from the switching.

I just noticed that for both the DRL and non-DRL Yaris the fog relay coil is tied directly to the body ECU internally in such a way that it prevents the fogs from turning on except when it decides it is OK to. You would have to either do some surgery on the body ECU or use an external relay and rewire the fogs to it to override that behavior.

[Absolutely Red 12]

Originally Posted by CTScott

You should use a four, not three wire switch. The illumination should be isolated from the switching.

I just noticed that for both the DRL and non-DRL Yaris the fog relay coil is tied directly to the body ECU internally in such a way that it prevents the fogs from turning on except when it decides it is OK to. You would have to either do some surgery on the body ECU or use an external relay and rewire the fogs to it to override that behavior.

Ok, Ill leave it like this for now.
The Chinese switch was a four, with isolated illumination. Wouldn't allow the fogs to turn off!! The three wire works as expected, Ill get another 4 wire to avoid future issues.

Thanks a bunch.

[CTScott]

Originally Posted by Absolutely Red 12

Ok, Ill leave it like this for now.
The Chinese switch was a four, with isolated illumination. Wouldn't allow the fogs to turn off!! The three wire works as expected, Ill get another 4 wire to avoid future issues.

Thanks a bunch.

The one that came with the kit has some internal circuitry which ties the switching and illumination together. What you want is one where the two are truly isolated.

[Absolutely Red 12]

Originally Posted by CTScott

You should use a four, not three wire switch. The illumination should be isolated from the switching.

I just noticed that for both the DRL and non-DRL Yaris the fog relay coil is tied directly to the body ECU internally in such a way that it prevents the fogs from turning on except when it decides it is OK to. You would have to either do some surgery on the body ECU or use an external relay and rewire the fogs to it to override that behavior.

Scott,

The green wire is the trigger when the head lights lights go on, the violet loops to the other row. Looks like the Violet triggers the fog realy, and dash light.
Im having difficulty finding the wire that is live when the park/low/high get selected.

Do you have a wiring diagram for 2012??

[CTScott]

Originally Posted by Absolutely Red 12

Scott,

The green wire is the trigger when the head lights lights go on, the violet loops to the other row. Looks like the Violet triggers the fog realy, and dash light.
Im having difficulty finding the wire that is live when the park/low/high get selected.

Do you have a wiring diagram for 2012??

The green wire is "activated" by the Body ECU, when it decided that it is OK to let the user turn the fogs on. Once it is active, shorting it ground (which is what the violet wire is tied to) at that time allows power to flow through the fog relay coil.

The blue wire in pin 18 is the one that is activated when the park or headlights are on. It is 12V with them off and then switches to ground with them on.