Bad ECM? Random issues

Hey everyone! So I am looking at buying a tundra. Its a 2007 4.7 2wd double cab with about 235,000 miles on it!

I checked the VIN and it has been serviced at Toyota its whole life up until about 220,000 miles.

Anyways the guy says it has a bad ECM. The issues are, windows won't roll down, the radio doesn't work, the AC doesn't work, and the speedometer doesn't work. It also won't hold a battery charge for more than 2 days. He said he has checked the fuses and wiring, and replaced the battery and alternator. Also Toyota service history shows they installed a new alternator about 4 years ago.

It appears to be in pretty good condition and have not a ton of miles on it. I went to school to be a technician for Toyota and took apart many Tundras. I was just wondering if anyone had any pointers or advice? It doesn't look like it was flooded or anything, and the title is clean.

Should I walk away or give it a shot and check everything out myself?

Thanks guys!

 

I sure wouldn't pay much for it! An ECM isn't exactly crazy money, what is preventing the current owner from fixing the truck?

What would be more scary is if wires are cut or modified to "repair" the problem.

Something like this would depend a whole ton of the actual person telling you this and what your gut says.

 

You start with wiring diagrams. See if the diagrams for the different problem circuits overlap at a common fuse or ground point. Pick the easiest circuit the doesnt work and figure out why it doesnt.

There is a post IIRC located in the General subforum that links to factory wiring diagrams.

 

Windows may be a TSB issue.. bad ECM i doubt it, light be a body ECU, but I doubt its that either.. most likely a rodent chewed something

 

Ecu? No. Wiring issue? Yes. Rodent damage, previous collision damage, shoddy aftermarket install (remote starts!) simply a rusty ground.. all these can cause the issues stated. A bad ecu, will not.


Now body control computer? Yes.


If the price is right, I’d jump on it, for it may be just a main fuse that’s blown. Or the gamble of a whole harness that needs to be replaced. It’s old enough that junkyard parts are out there for not too much money. So you may end up with a real winner if you get it figured out

 

Thanks for all of your replies! I have to drive it about 2 hours back to my house, is there anyway to keep a battery charged or a way to bypass the alternator for a short period of time and somehow charge the battery while I am driving? I don't really want to have to tow/trailer it home.

I thought about buying like 5 cheap Walmart batteries and swapping them in every half hour on the way home. But that's expensive.

 

I've gone through batteries as well.. it may be the alternator is overcharging the battery and has damaged some coils, or it may be the battery losing contact with the terminal, which I also get and wiggling the terminals will get good contact... You may get lucky and be able to charge it while the car is running, it may take like 30 minutes though... If you watch your idle and battery gauge check to see if you can hold the gas and brake and see if the battery gauge moves, you may be able to drive it home, but it may stall at some point in your drive, if the battery is done...

I was reading on the Celica forum about a dead alternator, they made it 30 minutes before it died, with traffic... i wouldn't recommend driving at night either, depending on where you live that may create a volatile situation...

 

I would walk away. Electrical gremlins are the worst.

 

Sounds like a fun wiring project to me! But you better have a some pretty solid wiring and electrical system knowledge, time, and tools at your disposal. If getting the truck back 2 hours is a difficult barrier to overcome, you might want to walk away. Or you're just looking for an excuse to walk away?

I couldn't find the wiring diagrams mega post, did it get taken down? Circled C infringement?

 

This very much sounds like a power issue. Most likely a bad fuse or bad ground wires.

I would start the truck with a volt meter on that battery post, if it doesn't read 14V or so its not charging. Evidence of an electrical issue.

You are not getting power to the radio, AC, cluster, almost anything in the interior. Look at every single fuse in the fuse box under the hood and the one under the dash. I use a multimeter on the continuity setting. If there is solid continuity between the leads the meter beeps if not its silent. Put a probe of the meter on each side of evey fuse. If it beeps its good, No beep is bad fuse.

This may help a little. He had to replace the main fuse but his also wouldn't run at all https://www.youtube.com/watch?v=6wpJ-b2qDSo