Help Locating an electrical problem

Hey everyone,

I did a bunch of upgrades just before leaving on a cross-country trip. About 300 miles in, after stopping at a rest area, I was greeted with a flashing 4wd light. I wasn't too concerned and figured I'd find it when I got to my destination. Well, in addition to that, I also found that with cruise control on, if it needs to slow down more than a few MPH, it throws a malfunction in the pre-collision system. this goes away after shutting the truck down, but it happens the next time it slows down. Techstream sees the 4wd switch change states on the live data.

Truck: 2020 TRD Sport

Codes:

• P057113 - Brake circuit A open
• P279E - 4WD Range Signal Circuit Range/Performance
• C1A4B - Stop Light Relay Circuit

Upgrades performed:

• Remove factory inverter - wired in new 2k pure sine wave inverter (under passenger seat, ran 120v to tie into original wiring which also feeds 4 additional outlets in cab. all other inverter wires disconnected)
• FitcamX dash and rearview camera (taps off of safety connect module)
• Removed factory JBL system / amp and replaced with Sony 9500ES system and amps
• New LED Tail Lights
• wired offroad lights to work with Fog and high beams (Diode on hot leg of light to positive of relay coil)
• Wired offroad reverse lights to work with factory reverse lights (I think this might be where my problem is - I tapped a wire in the driver kick panel(cut solder heatshrink) in one of the connectors that goes hot when reverse is on. Its run via a diode and relay, so there shouldnt be any backfeed or high draw, but its a likely problem spot as I dont exactly know what wire im tapped into ( perhaps not the best idea)Tapped into the connector shown here, however the pinout and color coding was different, so it was a different wire. Ill grab a picture next time i stop)
• Regeared with ECGS third members (5.29) These have a heck of a whine, but thats a different topic..)
• Tuned with overland Tailored tune

 

The red wire shown is the one tapped into. This is in the drivers side kick panel.

 

Any rodent signs in the engine compartment?

 

Not that i noticed. Is there a particular spot you are thinking? I can inspect it more closely

 

"but its a likely problem spot as I dont exactly know what wire im tapped into ( perhaps not the best idea)" Check this link from Car Care Nut on YouTube, newer Tacoma, but as example: https://youtu.be/FPKN25EpN6s?si=bTLONQzADqJ5dUAK

 

Though I understand what you are referencing with ccheap components, these are not cheap systems and are not wired directly into anything. Everything is tapped, ran through a diode to prevent flyback, then run through a relay to activate the associated item. the only pieces of hardware that are directly sconnected are the dash cam, and the swapped aftermarket tail lights, which are spyder assemblies.

If you are referencing this video for the troubleshooting steps, I can troubleshoot the problem without issue once i am to my destination. I am just on the road for the next 30h or so and was hoping someone might be able to point me in the direction of oh they all ground here, you probably undid that bolt and didnt tighten it all the way or something of that nature.

 

I never said you used cheap aftermarket parts, use this video as example. You wrote that you did not know what wire you tapped into. Most likely need wiring schematic to check things out. Lucky still be able to drive for the next 30 hours, not stuck someplace.

 

Understood, I do have all of the wiring diagrams for the truck, just need to find the right one regarding that terminal block.

 

Any of the harnesses and wires in the engine compartment- I have a 2017 so there are a few less than yours but it’s one of the things you should check when troubleshooting odd electrical issues with these trucks.

 

It is from the backup lamp switch that signals the ECU. it is the wire expected. In which case, i dont think its related.

 

Remove tap to added reverse relay, run Taco. Verify if issue continues.

 

I just did this actually at my last gas stop. same issue. I found diagrams, and see that this wire goes to the anti skid computer directly, so i am hoping I didnt screw that up. Im gunna go through fuses tonight when is top and see if those are bad anywhere. Fingers crossed

 

Remove battery ground for a system "reset"...

 

I am letting it sit overnight with the battery disconnected. Before I reconnect it in the AM, Ill disconnect the dash cam and check the ground under the dash. If that isnt it, its either the JB or the skid control ECU. Neither of which i am looking forward to replacing.

 

LED tail lamps have been known to cause problems similar to this, especially causing BRAKE errors and PCS problems. If you don’t have the stock lamps with you on your trip then you probably can’t do anything to rule that out though.

 

Ive had them for a few months now without issue, and dont see any reviews saying these cause an issue like this. That being said, I can probably find some bulbs to test since these lights plug into the original connectors.

I am unfortunately pretty sold on a popped skid control ECU given its directly tied to the wire i was tapped into for reverse lights, and it is common across the systems that are throwing codes. The more i think about it, the more it makes sense as I dont think the light was on when i backed out of the parking spot, then was on when i switched to drive. Perhaps the diode i used didnt block the flyback from the relay

 

tacomas dont like electrical mods