Opinion on 2011 Prerunner ECU issue

Hi folks. Just hoping I can get an outside opinion on this before I buy the part. I'll try to keep things short but informative...

A few months ago my truck failed to start after coming out of the hardware store. Again, this is a 2011 Prerunner. I tried jumping it and everything else I could think of, but wound up getting it towed back home. Had a buddy bring his meter by (OBDII) and we found that it wouldn't connect. Connected fine to his vehicle as well as my wife's, but no dice on mine. While checking a number of other things we happened to have the battery unplugged for a while. Hooked it back up, and after a few minutes it started, then died right away, then started and ran fine after that. Once running the meter connected fine and gave no error codes. Following that incident it would has had the same issue intermittently. I've had it to two "mechanics". One wanted to replace a relay (can't remember which one), and the other wanted to replace the starter. I'm no mechanic, but I don't believe that either of these things are the issue. And I didn't want to go down a rabbit hole of replacing random things hoping to eventually fix the issue.

Anyway - as the weeks have gone on I've noticed that it has taken longer and longer to restart after unplugging the battery (each time I do this it does the same thing btw... starts, dies immediately, then starts and runs fine for anywhere from a week to a few weeks). A few days ago it actually died while I was sitting at a traffic light. A good samaritan helped me push it into an adjacent parking lot. I was there for over an hour before it would start again. So my friend and I are thinking the processor in the ECU is getting hot and won't reset until it cools down.

Since we're not 100% sure I found a place online that will send me a refurbished ECU programmed with my VIN for a good price. That way if it winds up being something else I'm not out a fortune, and if the rebuilt one fails down the road I'll have no problem dropping the money on a new one if I know that's the issue.

Anybody have an opinion on our thought process here? Again... I'm no automotive guru. My friend grew up working on cars with his Dad (we're in our mid 40's), but this is a bit deep for him. I'd appreciate an outside opinion from someone who doesn't want my money.

Thanks In advance!

 

Lot more diagnosis is needed, first of all when you say it "fails to start" do you mean you turn the key and nothing happens or that the engine cranks but does not start running?
ECMs are expensive and one of the most robust pieces of hardware on a vehicle, very rare to one fail. Not that it doesn't happen, just very rare and definitely would not be the first thing I would suspect.
Again, more diagnosis is needed but my first impression is that it kinda sounds like the signs of a failing fuel pump.

 

Thanks for chiming in! I wasn't too descriptive with the "not starting" issue. Sorry. But yes... It cranks, and does everything but turn over. I was never sure if you were supposed to be able to hear the fuel pump in the key on-engine off position if the ecu isn't online to give it the ok. Fuel pump was my first thought as well. But when the OBD meter would not connect the ECU became our prime suspect.

 

Did either of those mechanics charge any fee for diagnosis?

 

I certainly hope not.

You need a good competent mechanic to test fuel pressure and try to get it to a crank-no-start situation and check that the the injectors and plugs are firing when this occurs. I would not even mention the ECM theory to a mechanic, if that's a problem they'll find it on their own but don't put it in their head before hand.

 

The guy that suggested replacing the relay did. But that was because he came to my house. The other one only charged me for towing it to his shop.

Thinking a bit more about the fuel pump... I've had one go out on a couple of previous vehicles, and that's always become and issue of them getting hot while the engine's running. This typically has only been an issue in the morning or at least after it's been sitting a while. I haven't driven it since it died on the road the other day - but that was the first time it happened while it was running. Just a thought...

 

The lack of obd communication is telling, throwing a pcm relay at it might not be a bad idea.

Dig around and check pcm grounds/engine grounds. Is the pcm connector secure? Corrosion on pins? Any codes present when the scan tool does connect?

On some pcms you can take a little inspection plate off and smell it, see if it smells cooked. I haven't had the pcm out in any of the tacomas ive owned so i cant really picture it but sometimes you can disassemble it and pull the circuit board out. Look at the board closely and see if there's any burned spots on it

 

I've not yet inspected the part. I'm actually getting ready to do that here this afternoon if the wife will give me a few minutes I'm just snooping around to find the location. If you think throwing in a new relay would be a good idea I'll go pick one up. And no - there are no codes given once the vehicle is started. This is confirmed by my friend as well as both mechanics that have looked at it.

 

Diagnosing pcms can be hard, especially if the issue is intermittent. When the problem is happening you have to check all the power inputs and grounds for the pcm. If its powered up and grounded and still won't communicate then its likely bad. But all that pinpoint testing is only useful if the problem is happening at that time.

If you're considering trying another mechanic, call around to a few shops and tell them whats going on. Ask them if they have the confidence to diagnose a possible pcm issue. Ask them if they have the ability to program a new one when it gets installed.

Good luck

 

Been meaning to get back to this. Sorry...

I went ahead and took it in to a third mechanic. This guy was actually a retired mechanic who was working part time for a chain of local tire shops that my grandfather started in the early eighties. I know the family he sold it to when he retired, so I took a chance that they'd treat me right and not run me around with a bunch of guess-work. Trying to keep a long story short here... I gave him permission to keep the vehicle for as long as he needed to, and to drive it to work and back. He had it for two weeks, and called me several times to check in and let me know what he was up to. During that time the issue presented itself twice. He checked several points in the fuse/relay panel under the hood, as well as the fuel pump. He removed my aftermarket stereo to see if something with the installation of the head unit or power amps might be causing an issue. Checked all the ground points he could find as well. He did not mention weather or not he had checked any of the points on the main ecu, but did wind up replacing it with a refurbished unit. I've been driving it a little over a month now with no issues. The shop charged me nothing, and the guy tried billing me for $500. Knowing that ecu had to have been in the $400 neighborhood, I felt better giving him $600. I feel like I made out pretty well. We'll see if it continues to run without issue.