2wd-4wd mode change failure saga

Hey Guys,

I am the once proud owner of a 2017 Toyota Tacoma. I bought mine certified pre owned from a dealership in May of 2019.

In that time, I have done some mods to my Taco to include some of the following:

• LED headlights
• Smoked tail lights
• Raptor style grill lights
• LED lights on the interior (map lights and vanity lights)
• LED license plate light
• Aftermarket stereo (plug and play replacement
• Remote start-done at a local shop
• I also had a local shop do a lift, as well as new wheels and tires. In addition to the new tires, I put in the plug/play speedometer adjustment piece.

The last of these modifications where installed around a year or so. The truck had been functioning flawlessly since. No issues whatsoever with the 4wd. Of course I am around 2 years from the date of purchase, so I am outside of the comprehensive warranty coverage phase.

A month and a half ago, I was driving over a mountain pass in heavy rain conditions. As I was leaving the pass, I got an error message that said “2wd-4wd mode change failure”. This error message popped up without any turning of the knob, or any attempts to go into 4wd. Sure enough, the error message persisted despite several restarts and attempts at spinning the knob.

I took it to my dealership. They had it for a couple days, and they described the problem as “intermittent” and they were having trouble trying to get it to come back up reliably. They called me and said they were going to return it. They put it in the wash, and the message popped back up.

Since then, they have had it for over a month. They have tried switching out ECU and also tried tracing the wires from the ECU to the differential. They initially thought that there was a problem with a faulty wire in the ECU harness, but that apparently was not the problem.

Their new train of thought is that they believe it had something to do with the aftermarket stereo. They unhooked the stereo with no luck.

Their expert technician, or whoever they are consulting has instructed them to try to revert all of the modifications to stock. They warned me that this would be costly and likely take a lot of time.

I’m starting to get a little frustrated. I know it’s a long shot, but anyone experience or hear of anything similar?

 

I wonder if its the electronic doohickey that changes from 2wd-4wd people have had issues with water getting in it.

 

Did they inspect the actual 2wd vs 4wd shift module? Those can take on water and rust.


Also, @ShimStack and @BigWhiteTRD

 

Problem was intermittent, then it suddenly popped up when the original situation that the problem presented itself in was simulated? How ‘bout that.

Definitely sounds like a water ingress problem, not a revert all the mods and then see what happens problem. I agree with those above.

 

One of the first things I did was seal the actuator.

Toyota replaced 2 actuators on my friends 2016, sealed the 3rd and he never had a problem since.

 

Did you happen to see any corrosion in those units? About how much was the part?

 

My thoughts exactly. Although I will be the first to say that I am not terribly car savvy. I kind of assumed that would be the first place they looked/inspected...especially if they are so confused that they are talking about removing headlights to fix a 4wd problem.

I don’t wanna seem like an asshole by suggesting how they should do their job...but I guess it’s worth asking if they’ve looked into that part of it.

 

I’m not confident if they have actually looked at that unit itself. The signs do point to water related though. Especially with how it started.

 

There's a YouTube video of someone removing and sealing there's. Worth a watch

 

I just got off the phone with the dealership. Apparently that was one of their first steps, was to inspect the actuator. They claimed to have tested several different ways, and it appeared to be functioning.

 

Not on mines. I had mines done about 5k miles. My friends was done by Toyota, on Toyota. But I will say that his has seen many a salty, muddy puddles haha

 

Sorry to hear the story.

It is basically impossible to not 100% blame the dealer at this point (if they are a Toyota dealer)
Techstream will narrow this down to which actuator, and in that actuator which feedback or motor circuit is the culprit (although it wont tell if the problem is at the ECU, in the wiring, or in the actuator)

From there, you just decide how to tackle the problem (swap parts from good vehicle, disassembly and inspection, shotgun it, etc)... It is really unconscionable for them to have not fixed it by now, unless there is a significant part of the story we arent getting.

I recommend getting it away from that dealer, even if it costs you some money to fix it yourself...
Either get techstream yourself, or take it to another dealer and pay for some techstream diagnostics.
(It is also possible to do some troubleshooting with a volt meter at home, but not recommended for intermittent problems, if it really is intermittent.)

Based on antecdotal evidence, there is about a 95% chance the issue is a bad connection internal in an actuator, like 85% chance the ADD actuator of the two. 5% chance in wiring under the vehicle, and probably readily visible.... Never seen a proven bad 4wd ECU on 3rd gen, so negligible chance there.

(2 cents)

 

I wonder if your dealer is trying to weasel out of fixing it for you.

 

Any dealer that tries swapping ECU's early in the troubleshooting process is a garbage operation. Odds of that being the problem are close to zero. Follow @BigWhiteTRD 's suggestions and run fast. The troubleshooting process isn't this difficult unless you're highly incompetent.

 

Any luck OP?

 

Beat me to it.

But by all means, if that dealership thinks your led raptor grill is causing the 4x4 actuator error message....

Also check your harness connections behind the glovebox. If one of the pins/harnesses isn't fully seated, it can cause error messages.

 

Thanks for the responses. When I posted this, I had already told them to go ahead and do what they were gonna do. With how big of a production this has been, I didn’t want to give them any excuses if they decide they can’t fix the truck. I haven’t heard anything about it this week. Makes me real concerned for what the next step is if that fails.

I asked again about the 4WD actuator. They claimed that was one of their first steps, and that they had “tested it 15 different ways”.

 

About 4 weeks into this whole thing, they did mention that there was a wiring harness that appeared to have a bad wire in it. They said they would need to replace the harness/wire. They did this, but apparently that did not solve it. Makes me wonder what they actually found.

 

I just spoke with them again (they still have it). The tech removed the inline speedometer calibrator that went with the lift/tires.

They say they have not experienced issues since…

 

Those are completely unrelated.... Weird....

Unless it was throwing off whatever speed sensor the 4x4 computer uses to prevent itself from switching at too high of a detected speed.