It all started with a P2121 Error

TacomaWorld! I need help.

Driving back from Sparks, NV and just came over Donner summit. Check engine light AND A-TRAC light both came on. Power cut to what felt like a quarter and truck wouldn't rev over 3k. Limped all the way home which was sketch.

Went to Autozone and read the error code. Came up with P2121 which is the Throttle/Pedal Sensor. I came home and researched possible issues. Thanks to Tacomaholic, the next day I disconnected the battery, cleaned the MAF, cleaned the throttle body, and reset/relearned the gas pedal. Reconnected battery and low and behold, check engine light was off and truck ran great.

The next day in the evening, my across the street neighbor came over and told me that my headlights were flashing. Sure as shit, I went outside and the headlights flickered on and off at totally random patterns. And I mean totally. I disconnected the battery and let it sit there till today.

Today I reconnected the battery and fired the truck up. Headlights were stuck on high. Highbeam indicator light was lit on the dash and I couldn't get it off. Fog lights wouldn't come on in any position except the off position and then the fogs would flicker slowly like The Haunted Mansion. Also in the off position, I could hear this weird high pitched buzzing from under the hood. Discovered that it was coming from my headlight relay. Pulled the relay and the buzzing stopped.

So I thought the relay went bad so I went and bought another one. As soon as I went to plug it in, the high pitched buzzing was there which sounds like someone is playing Operation in the fuse box. I have no clue what the hell it could be although I had recently installed my lighting controller(S-POD knockoff). I totally disconnected this controller today before trying to chase down the lights so I don't know why it would be that unless it somehow damaged something else in the truck.

I am at wit's end and unless someone here can figure it out, I see an expensive trip to the dealer in my future...please help. I have a video that I took but can't frickin figure out how to post it on this forum. I will share it with whomever asks me for it. Thanks.

 

Sounds like you may have a bad ground somewhere, I'd start by checking all the ground point's you can find. If using a voltmeter you want to be connected from battery ground to the ground point you are testing it should read no more than about 100mv, If using a test light go from battery negative to the ground you want to test the light should NOT light.

 

It's the Body ECU. That is what controls the headlights.

 

Thanks for chiming in guys. So...for the body ECU, do you suspect that it needs a reboot or that it is junk parts? Another question is what would make it go haywire? Just a coincidence with me installing the lighting controller or did I "cross the streams" somewhere?

 

Check your powers and grounds at the body ECU before you condemn it, I've seen bad power and ground feeds cause some weird things to happen.

 

https://www.tacomaworld.com/threads/brights-dont-work-flashers-do-help.678822/

The body ECU is on the back side of the in cab fuse panel to the left of the steering wheel.

 

Alrighty. I will check my grounds and power. I had to disconnect both in order to hook up my lighting controller.

 

Alright boys and girls. Yesterday, I cleaned the crap out of the ground right by the fuse box and the other ground from the wiring harness to the frame rail. Wire brushed like there's no tomorrow. Fired it up and low and behold! No issues with the lights. No check engine lights. Blows me away that it was something so simple. THanks for all the help.