cruise malfunction 2001 trd v-6

I have reviewed some similar threads related to specific electrical problems, but here is mine....when my lights are on(even parking lights) the cruise control will not engage even though the green dash light is on. When the lights are off it works fine. If the cruise is engaged and I turn the lights on, it cancells the cruise. this problem has fixed itself occasionally ,but always malfunctions again. Also my abs light comes on sometimes but goes out if I turn truck off and restart.
I have read and heard from toyota that the wiring harness is most likely the culprit, but it is fairly new and was not a problem before. I think winter corrosion.......any thoughts?
Are the dash lights supposed to come on when the truck is off and you depress the brake pedal?

 

Uhhhhh ... No.

You've probably got a short circuit somewhere in the rear lamp units or the associated wiring. Current from the brake light circuit is crossing over to the taillight circuit. The dash illumination lamps are powered off the taillight circuit.

Conversely, when you turn on the lights, current is crossing over from the taillight circuit to the brake light circuit. My guess is that current on the brake light circuit is feeding back as far as the stop light switch and tricking the cruise control ECU into 'thinking' the brakes are being applied. That explains why the cruise control disengages (and can't engage).

If you've got a trailer harness installed, that would also be a likely culprit for the location of the wiring fault.

 

It was the trailer harness. after disconnecting it everything was back to normal. I found corossion on the left taillight connection. thanks for your help.

 

This was the perfect thread!

 

I love it when a diagnosis hits the mark on the first pass!

 

Hillarious! I had to assume I was the only one who has ever experienced this problem. I actually bought a 20 pack of 10amp fuses because when I would engage cruise at night with the lights on...it would blow the 10 for my tail lights. One warning ticket later and I thought I better carry some spare 10amp fuses ha! Till I read this post, I just modified my behavior. At night...I don't use cruise. In the day, I turn the lights off all the way and use cruise. Problem ?solved? ha!

Another interesting gremlin that I had for a bit was that in order to get the radio to turn on I had to very very slightly crack the driver's side rear window. Instant radio on. That went away. I also noticed at night that when the 10amp for the rear tail lights blew out that my dash was completely black until I hit the brakes. So, till I got a call from a buddy behind me one day...I just used to use my cell phone light to see my speed or tap the brakes. Yeeesh!

After reading this thread, I am certain this is due to the wiring harness that is literally hanging down behind my truck out of the tail lamp area. I've backed this thing down in the water one too many times I guess. Oh well. Anyone need to buy some surplus 10amp fuses

 

Way to hit the mark on that diagnosis. This was a perfect thread!