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Juan Crespo
Juan Crespo, Tech Trainer
Category: Toyota
Satisfied Customers: 1526
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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2008 Tundra....brake lights come on when accessories or truck's

Customer Question

2008 Tundra....brake lights come on when accessories or truck's turned on, but when it's turned off they work properly.
JA: Sometimes things that you think will be really complicated end up being easy to fix with a Toyota. The Toyota Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.
Customer: Thanks Pearl
JA: Are you hoping to fix this yourself?
Customer: Yes ma'am....
JA: Great! What have you tried so far?
Customer: Checked all connections to trailer hitch and tail lights....seems to be in good shape
JA: Is there anything else the Toyota Mechanic should be aware of about your Toyota?
Customer: It has a camper shell, with led brake lights that I had just replaced....when I hooked it up this happened.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Toyota Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Toyota
Expert:  Juan Crespo replied 1 year ago.
Hi there.Are the trailer hitch and all associated wiring and connectors OEM? Do the brake lamps work as designed if you remove the trailer connection?
Customer: replied 1 year ago.
The trailer hitch is aftermarket.
Expert:  Juan Crespo replied 1 year ago.
Thank you for that information.LED lights use considerably less electrical energy than conventional incandescent bulbs and as such can affect circuit voltages, specially those connected to electronic modules as is the case with your Tundra.My advice is to remove the LEDs and re-install the original bulbs. If that restores normal brake lamps function, then make sure to get LEDs that have the same electrical power requirements as the original bulbs - places like NAPA sell LEDs that already have resistors in them that equal the resistance of conventional bulbs.Best Regards.
Customer: replied 1 year ago.
I unhooked the led lights, and it's doing the same thing now....brake lights come on when truck's started.But when it's off, the tail lights & brake lights work properly....turn on & off as they should.It's only when the truck's turned on this is happening.
Customer: replied 1 year ago.
Seems like some sort of repay to me, if it's only when turned on, but I don't know what relay it could be?
Customer: replied 1 year ago.
repay = relay
Expert:  Juan Crespo replied 1 year ago.
Please give me a few minutes to look at the diagrams. Be back in a bit...
Customer: replied 1 year ago.
Thank you sir
Expert:  Juan Crespo replied 1 year ago.
OK. With the key off, please go to the relay panel under the hood and put your fingers on both brake relays (see attached graphic). Then have a helper turn the ignition on and tell me if only one (and if so, which one) or both relays click(s)
Customer: replied 1 year ago.
Ok....I can't tell which is clicking, or if both are. I can hear it and feel it, just can't tell which one it is.Give me a minute.
Expert:  Juan Crespo replied 1 year ago.
Take your time. Unplug each one at a time if it makes it easier.
Customer: replied 1 year ago. do I unplug it?
Expert:  Juan Crespo replied 1 year ago.
They're supposed to just pull out...
Customer: replied 1 year ago.
Ok....I think they're both clicking.
Expert:  Juan Crespo replied 1 year ago.
OK. So both click as soon as the ignition is turned ON, no one pressing the brake pedal?
Customer: replied 1 year ago.
Yes....didn't touch the brake.Did find out when I start the truck, then turn the engine off and leave accessories on the lights work properly.But if I turn the accessories on from the off position the brake lights come on.Weird.
Expert:  Juan Crespo replied 1 year ago.
Well, looking at the diagram and assuming the wiring hasn't been disturbed, I would have to point to the Skid Control ECU as the possible source of the issue. To confirm, go ahead and disconnect that unit (see attached graphic). We'll know we're on the right track if the brake lamps no longer come on when the ignition is on.
Customer: replied 1 year ago.
How do I disconnect it?
Expert:  Juan Crespo replied 1 year ago.
Should be a Bosch-type weatherproof connector that locks with a metal clasp. I'm trying to find a picture for it...
Customer: replied 1 year ago.
Expert:  Juan Crespo replied 1 year ago.
Couldn't find one for your Tundra, so I've attached a similar one for a Forerunner so you can get an idea on how to unlock the plastic clasp and disconnect the connector.Now, please don't shoot the messenger, but there is a good chance the Skid control ECU is the source of the issue with the brake lamps (not uncommon on these trucks). Thing of it is Toyota recommends replacing the entire actuator assembly as the proper repair - last time I checked price on one off those a few years ago it was around $2000.Best Regards.
Expert:  Juan Crespo replied 1 year ago.
It's past my usual log-off time. I look forward to hearing from you again tomorrow after 2 PM AST.Best Regards.
Customer: replied 1 year ago.
No worries at all, I ppreciate it....ill give it a shot in the am...thanks so very much
Expert:  Juan Crespo replied 1 year ago.
Thank you and Good Night!