You were close! Just heard from shop #2 that it was the O2 sensor harness got fried by my exhaust, which was shorting out the EFI circuit. They're re-wiring the harness and then securing it away from the exhaust.

Hot dang!

This car wash have heavy side or undercarriage jets or was this just a coincidence that it went out after the wash?
I wonder if it had already suffered damage and the wash just exposed the short?
Lol I'm sure you don't care at this point, but it's good to document this type of bs for the forums sake. Glad to hear it! @waypoint Good Stuff!

The undercarriage jets are the reason I go to that wash lol

Here's my educated guess; a couple months ago, the metal heat shield that goes around the driver's side catalytic converter that's on the exhaust manifold fell off (Exhaust shield hitting my driveshaft!). I looked at it and it was shoddily cut at the top from the shop that installed my DT headers to the point where there was only one small part of metal keeping it on.

Anyway, it was rattling like heck and hitting my drive shaft, so I had to pull it since I didn't have a way of securing it back to the cat. My guess is that somewhere in that process or because of that, the heat shielding on the O2 sensor was damaged. I had just taken the truck on a 6 hour drive down to Ouray, off-roaded it for a week, and came back. It was a long and hot drive back...

I'm getting it back tomorrow so I'm going to ask which side it was, and if it was driver's side then it'll make a lot more sense.

I'm just really glad it wasn't a bad ECU since shop #1 said it could be that but they didn't have the equipment to reprogram that stuff (which is funny because it's just Techstream, and I have that on a laptop).

Wow, that could have been a DEEP rabitt hole. I missed your post about the o2 sensors and didn't remember you had the header install, I was headed the wrong way too lol. Sorry about that.
New ECU? That woulda SUCKED! Just glad your making progress!

What OS you have running the techstream? I haven't jumped into that pool yet, relying mostly on the forum and Torque Pro app for diagnosis and live data on my 4th and 5th gens. I need a new distraction with all the crap going and unemployment to boot.

No worries at all! I clearly had no idea.

I got Techstream in some bundle package with a cable on Amazon I think. I have it running on an XP VM which is pretty funny considering how old it is. It’s actually a VM running on a Bootcamp Windows 10 on a Mac laptop. So a VM on a VM.

It’s super useful though, and it saved me a boatload when I reset my Immobilizer and programmed new master keys since the car only came with a valet.

You’ll have fun with it!

Congrats! It's likely they found a blown fuse, replaced it and saw it immediately blow again, then went looking for wires touching metal. You have a good shop to work with assuming they don't rape you on the bill.

The weird thing is that I checked most of the fuses (specifically the A/F related ones) in the fuse box, but I think the EFI is one of those weird box relays and I'm not sure how to actually check those. I think if I was doing it at home and caught that, I would have replaced the relay, had it blow again, been pissed, and then been at a loss as to why because I wouldn't have known what else was on that circuit to check. However, I know I would have started next on the O2 sensor that was throwing the code and I probably would've seen that messed up wire harness, but I've never replaced a wire harness so I would've chickened out.

They are a good shop for sure (Toy Doc in Denver if anyone ever needs it), but a bit pricey on some things and they do this safety check on everything which ends up with quotes that are pretty high. It was $300 all said and done, which hey, is cheaper than a new ECU, but...dang. I think they usually run just slightly cheaper than a dealership, but not as cheap as other places. Then again, I'm a believer in you get what you pay for, and cheap shop was way off the mark on this one. hah

It's like my granddad said: "Good help isn't cheap, and cheap help isn't good."

Yep, so far it's held true for me as well. I wish it didn't, but I get reminded every time. That's why I just go OEM for the parts too.

Speaking of which, now I'm not sure if I should try to sell this brand new OEM MAF I put in there, or just sell the old one, or just keep it. I'm afraid to pull the new one out to test if the old one still works now for fear of breaking everything again haha.

^ Back up electronics are nice to have for diagnosis and just in case of emergency. You never know how long a part like that will be available sometimes.

Digging up an old thread, but I came across your thread about your MAF Sensor woes and your 4Runner being stuck in limp mode. Sounds like I have some similar issues. 2 tries to start (unless I turn key to on and sit for a minute), and it won’t go over 3k rpm. Wondering if you had any suggestions on first thing to check. Think it’s the fuses or the wiring harness? I’ve already replaced both downstream O2 sensors based on a P0430 code and replaced all the spark plugs but the issue is still there.

Trying to avoid taking it to a shop, but also in Denver so could try ToyDocs if that’s my best option.

Aw man, sucks to hear you're having this problem. So I'm not sure if I ended up posting the end result, but the downstream O2 sensor harness on the passenger side was melted from contacting the transmission. ToyDocs ended up fixing it for like $170 by wiring in a new sensor and hanging it higher with a couple zip ties. It's been a couple years but it's held!

Hope you can get yours sorted.