Weird electrical problems, looking for a common point.

Hi everyone,

Been a long time since I've been on the forums, but I feel like I've exhausted every avenue. None of the links to FSMs on the other 4runner forums seem to work, and as I've left the automotive industry I no longer have access to ProDemand.

This is a 2008 4Runner V6 Urban Runner that is pretty stock. I have an OME lift and aftermarket radio I put in 5+ years ago with no issues. I put Lasfit LED lo-beams and Morimoto 2Stroke 3.0 LED fogs over a year ago.

TL;DR - My wipers and headlights will come on with the vehicle off and key in my pocket. The HVAC display screen stays on after the car is off, and sometimes the blower motor will stay on too. Is there a common point for all of these?

So here's the story. I got another 4runner, and I drive it recreationally more so than daily. It sat for a few months and I had a bad battery, no big deal. Replaced it. Left for work one day in a torrential downpour in my Honda, and at the front of my neighborhood, my crank pulley snapped, so I got it home and took the 4runner. I get an email from our building admin, stating my wipers and lights were on. Went to check it out, and sure enough, they were on. When I got in the car, the HVAC screen was showing the clock. I've visually inspected everything, checked all grounds in the engine bay, checked fuses, and isolated the ignition switch entirely. Nothing will turn the HVAC screen off. A few days ago, it miraculously just worked. No symptoms, no battery drain, nothing. Went to start putting the dash back together and I have to jump it. Then that damn HVAC display is on again.

Anything else I should check, or does someone have access to the wiring diagrams?

 

Further testing revealed that removing DOME and ECU-B fuses on main junction block, and ECU-IG and IG1 fuses on the interior (all independently) shut the screen off.

Edit: if I isolated the ignition switch fully, should any ecu/ig fuses mean anything? I understand that ECU fuses will shut the whole damn thing down, but ignition fuses are shutting things off regardless of the ignition switch being connected or not

 

Is it possible that the Body ECU got water to it and got shorted out when it was raining so hard?

This can happen when water gets into the kick panel area from either stopped up moonroof drains and or going through deep water.

I would inspect the wiring connections to the ECU for signs of wetness.

 

Just on research/tear down I did, I couldn't tell if the BCM was separate from the ECU. Is it a separate unit? Where is it located? Is there any testing procedure or am I left to guess and check?

Also, I should note - my sunroof drains were clear when I checked them.

 

Do you still have the OEM head unit? I’d swap that back in to check if the aftermarket unit is causing problems.

 

I do, but I don't have the connector lol. It had the eclipse with the tomtom unit, and I installed it years ago before they made adapters for it.

Do you really think that it would start showing issues 5 years later?

Also, I guess I could just pull it out and see if that changes anything

 

Electrical gremlins never play fair and can be a patient bunch. Given your situation, with all else equal the head unit is the only thing that you’ve changed…can’t see the Morimotos creating an issue (unless you’ve got them wired in with some wacky add-a-fuse method - I’m joking of course!)

Of course the only way to be sure whether the gremlin resides within the factory ecosystem would be to remove the aftermarket head unit, the Lasfit and Morimotos…