Battery Discharge - Need New ECM

[Obadiah]

Okay, I have 04 4Runner with ~78k miles on it. From the time I purchased this vehicle from the dealer it has had issues with the charging system. At first it was intermittent and it began as the warranty was ending.

After about 3 years I figured it was just the battery that needed replacing so I replaced the OEM Panasonic battery with an Optima battery. Shortly after I replaced the OEM battery with the Optima I noticed the vehicle was again draining the battery. I went to the dealer and they charged me $40 to recharge my new Optima battery and tell me nothing else was wrong.

Just 8 short months later the 4Runner was discharging again and the new Optima battery would be dead the next morning. I thought I had a defective Optima so I then replaced that with a Sears DieHard Platinum battery ($200).

Now the DieHard battery is starting to discharge again and I find it dead on some mornings. I went to the dealer to complain and they charged me $150 to do a thorough fuse-by-fuse type test. They determined that it was my aftermarket electric brake controller that was drawing too much power. Fine, I disconnected it and thought the problem was solved.

Now, my 4Runner is once again discharging and the battery is dying so obviously the car was again misdiagnosed so I brought it in to the dealer a 3rd time.

This time the dealer charged me $210 and told me that the Electronic Control Module (the car's main computer brain) was not properly turning off and that it had to be replaced. The cost for an ECM? $600 plus about $300 to install it. Wow!

So a total of 2 new car batteries ($350) three diagnostic service charges ($400) and now a new ECM unit installed (~$900). For a total cost of $1,650 to fix my 4Runner that had a battery charging/discharging issue since the day I bought it.

I will say that Toyota is stepping up and contributing $370 towards the cost of a new ECM, but I have all the documentation proving that this was an ongoing issue and that it is a factory defect.

I have heard of a number of other Toyota vehicle owners who have had an identical, long-term mysterious discharge issue and that is why I am documenting my experience and what appears to be a final solution - a defective electronic control module (ECM).

 

[DC runner]

Wow. Are you even sure it is the ECU doing this? Sounds like they are guessing and just moved to the next area.

If you ECU was busted and not "turning" off, then I have to assume you would be throwing codes or seeing some other erratic actions. The ECU is a chip configured computer. It isn't like a personal computer that turns on and will just sit there, idle. The ECU is designed to look at, and do very specific things.

If the ECU is pulling power to the degree it is killing your battery in a short time (overnight, few days) then that ECU would have to be in an active mode..... surely that would manifest itself in obvious ways. Codes. Wacked driving. You MPG computer being all haywire???

Are they even 100% sure this is the issue? As for battery dying.. is there anything else aftermarket on your truck? Audio? Sub.. anything that could be pulling power?

 

[chaz]

years ago i had a vec. that did pretty much the same thing, every 3 days there wasnt enough juice to start it, & never could find the source of the drain, so i purchased a deep cycle battery & battery tender , installed plug on it & just plugged the charger in every night, worked for years.

 

[Obadiah]

Wow. Are you even sure it is the ECU doing this? Sounds like they are guessing and just moved to the next area.

If you ECU was busted and not "turning" off, then I have to assume you would be throwing codes or seeing some other erratic actions. The ECU is a chip configured computer. It isn't like a personal computer that turns on and will just sit there, idle. The ECU is designed to look at, and do very specific things.

If the ECU is pulling power to the degree it is killing your battery in a short time (overnight, few days) then that ECU would have to be in an active mode..... surely that would manifest itself in obvious ways. Codes. Wacked driving. You MPG computer being all haywire???

Are they even 100% sure this is the issue? As for battery dying.. is there anything else aftermarket on your truck? Audio? Sub.. anything that could be pulling power?

Well you raise some good points. I'll certainly raise those with the dealer. But yeah, that's what the dealer told me, that the unit stays in active mode and doesn't power down. Not always, but just enough were it will lose all battery over the course of a day or a few days.

Are they guessing? Man I hope not. The Toyota district rep authorized chipping in $370 so I hope this is more than just a guess! But they certainly did guess or assume on previous occasions.

And yes, while I haven't purchased a deep cycle battery I have had the vehicle plugged into a battery tender more times than I can remember -- nearly every night in the dead of winter.

 

[BlackWorksInc]

I am curious to see how they are testing your system? An ECM sounds plausible... but it seems rather strange the progression of their diagnosis.

 

[tsonnenl]

FYI - The ECM is right behind the glove box and is fairly easy to get to. 6 or 8 screws, and you'll have it out in 15 minutes. You'll have to pay for an hour of labor or so for them to flash the new ECM to match your immobilizer, but you can save 200 bucks on the install without much hassle.

 

[zstampe]

years ago i had a vec. that did pretty much the same thing, every 3 days there wasnt enough juice to start it, & never could find the source of the drain, so i purchased a deep cycle battery & battery tender , installed plug on it & just plugged the charger in every night, worked for years.

Ha! I like your style! Sounds like something I'd do.....

 

[Obadiah]

FYI - The ECM is right behind the glove box and is fairly easy to get to. 6 or 8 screws, and you'll have it out in 15 minutes. You'll have to pay for an hour of labor or so for them to flash the new ECM to match your immobilizer, but you can save 200 bucks on the install without much hassle.

Yeah, I thought about that but from my search an ECM for my 4Runner costs about $495 not including any possible shipping charge. With Toyota kicking in some cash my final cost to the dealer - according to them - will be $540. I'll spend the extra $45 and let them do it. They also warranty the ECM and the work for 1 year.

Also, if they just guessed and I still have a discharge issue it will be fun to watch me light off some fireworks at the service desk.

 

[lexusnut]

Yeah, I thought about that but from my search an ECM for my 4Runner costs about $495 not including any possible shipping charge. With Toyota kicking in some cash my final cost to the dealer - according to them - will be $540. I'll spend the extra $45 and let them do it. They also warranty the ECM and the work for 1 year.

Also, if they just guessed and I still have a discharge issue it will be fun to watch me light off some fireworks at the service desk.

Curious, was this ever resolved? Sounds to me like some wire short or relay is engaged and keeps nonessential part active. Or ghosts... maybe try holly water ray2: