Radio Upgrade Damaged ECM [Need Advice/Info]

[fazio93 10+ year member]

I had a 2005 Toyota Corolla with a stock head unit. When removing it, I disconnected the negative battery terminal and unhooked the wiring harness/antenna. However, the next morning I noticed the car was shaking and hesitating when idling. The next day I installed the after market head unit (using the Scoshe wire harness), once again, disconnecting the negative battery terminal. The radio worked fine. The next day the car quit on me in the school parking lot. It would just start up and stall out after a couple seconds. My dad and the tow truck guy both thought the fuel pump had failed. We brought it to an auto shop. They put in a new pump and the car still didn't start. The mechanic then diagnosed it with an ECU/ECM (however you want to abbreviate it - the car's computer) as the problem.

Good thing that Toyota has the 8yr/80k warranty on the ECM. I am going to get it towed tomorrow to toyota and they will take care of it.

The Corollas (especially around 2002's) have an infamous history for ECM problems. However I'm 99% sure this was a result of my radio upgrade. I read this where it was explaining how to get a stuck disc out of the stock player but it had some interesting information:

"The other method is to disconnect the power to the head unit for a few minutes and then power it back on. It should spit the CD out. Drawbacks of thismethod are dependent on what equipment you have on the circuit at the time and how you pull the power. Disconnecting the battery is the easiest method - but you will lose time, possibly lose ECM parameters (will run a bit odd until it "relearns"), if equipped with an alarm system (headunit, kill switch, pass keys, etc. - may do all kinds of weird things). To avoid those issues - just pull the fuse leading to the radio (should be listing in the operating manual). My fuse was located by the driver's side kick panel and was marked RADIO."

Toyoland - Toyota Corolla common repairs

Were the repeated battery disconnect the cause of a faulty ECM? I still have work to do on the car and I don't want this happening again once it's fixed. Would the fuse removal solve this? I've never read anything about this in any guide/tutorial. Please Help.

Thanks,

Nick

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[Blasphemy 10+ year member]

Were the repeated battery disconnect the cause of a faulty ECM? I still have work to do on the car and I don't want this happening again once it's fixed. Would the fuse removal solve this? I've never read anything about this in any guide/tutorial. Please Help.

That was probably the reason. If Toyoland said to take the fuse out, it's probably a good idea to do it.

 

[fazio93 10+ year member]

i just found this thread about resetting the ECU. it looks like many people had the same problem as me

Resetting the ECU - Toyota Owners Club - Australia

 

[nateberrier 10+ year member]

I have no experience with toyotas but in my 08 Pontiac I know that disconnecting the batter causes the computer modules to act funny sometimes, it will set off my airbag warning, my gauges with flutter, the car will stall, etc. Most newer cars, esp GM have lan systems not unlike the one your computer is connected to. Removing the radio or using an incorrect harness can cause all sorts of problems. Do you have a link to the harness you bought? Even so I doubt that your radio install trashed your ECM.

In addition to what you said, there does seem to be a good amount of documentation on a bad set of ECMs for your year and model. If you take the car in to the dealer for replacement do be sure to put the stock radio in or they could put you at fault and void the warranty.

Edit: you guys found it.

 

[fazio93 10+ year member]

I have no experience with toyotas but in my 08 Pontiac I know that disconnecting the batter causes the computer modules to act funny sometimes, it will set off my airbag warning, my gauges with flutter, the car will stall, etc. Most newer cars, esp GM have lan systems not unlike the one your computer is connected to. Removing the radio or using an incorrect harness can cause all sorts of problems. Do you have a link to the harness you bought? Even so I doubt that your radio install trashed your ECM.
In addition to what you said, there does seem to be a good amount of documentation on a bad set of ECMs for your year and model. If you take the car in to the dealer for replacement do be sure to put the stock radio in or they could put you at fault and void the warranty.

Edit: you guys found it.

i bought this harness:

Amazon.com: SCOSCHE TA02B Wiring Harness for 1987 and up Toyota: Electronics

it fit fine and the radio worked immediately.

and yes, i planned on sliding the stock radio back in before going to toyota.

 

[fazio93 10+ year member]

ok after reading online about people with very similar problems as mine, i'm convinced that something went awry in the ECU when i disconnected the battery (which is why is started hesitating the day after), not only disconnected once, but multiple times. i think it might just need a reset by disconnecting the battery for 30 minutes and then letting it idle for a few minutes after. i'm going to try that tomorrow before it gets towed to the toyota dealer (i wish i had it with me now to try). and even if it is brought to toyota, i'm betting that the techs will do the same thing.

 

[Blasphemy 10+ year member]

You are correct that the techs at Toyota will probably do the same. The ECU just has to relearn how to run the engine properly after it has been disconnected from power for awhile. I had the same problem with my Regal, I just kept driving it and after about two days (my car is older and it has a slower computer), it drove fine after that.

 

[fazio93 10+ year member]

Well it was toed to Toyota today and sure enough, the ECU had to be reset just like I had guessed. The fuel pump was still good, the ECU just wasn't telling it to do the right thing I guess.

Anyway, I don't if it's just paranoia, but I still seem to feel a slight vibration when idling in drive. I opened the hood and the engine was shaking a lot less than it had before. I compared it to my mom's 2006 honda accord v6 and she has barely any vibration at all. i know there's a lot of factors involved like engine type and all but the guy at toyota supposedly drove it for 10 miles without a problem. do inline 4s shake more than v6s? i'll see how it goes.

 

[DammitJames 10+ year member]

pretty much it has all been said... some cars have to be learned after it looses power drive it for a few days or take it on a 20 mile or so drive in regular traffic and see how it acts mid 90s GM where bad about having to be relearned

 

[Blasphemy 10+ year member]

pretty much it has all been said... some cars have to be learned after it looses power drive it for a few days or take it on a 20 mile or so drive in regular traffic and see how it acts mid 90s GM where bad about having to be relearned

Fuck mid 90s GM, that's what I have. The relearn process on my car took like two days of stalling out at red lights, stop signs, etc. //content.invisioncic.com/y282845/emoticons/pissed.gif.9f665f96bc89e98e708dabd4580bb591.gif

 

[DammitJames 10+ year member]

Fuck mid 90s GM, that's what I have. The relearn process on my car took like two days of stalling out at red lights, stop signs, etc. //content.invisioncic.com/y282845/emoticons/pissed.gif.9f665f96bc89e98e708dabd4580bb591.gif

lol yeah i agree

 

[QuikSilverRS91 10+ year member]

Fuck mid 90s GM, that's what I have. The relearn process on my car took like two days of stalling out at red lights, stop signs, etc. //content.invisioncic.com/y282845/emoticons/pissed.gif.9f665f96bc89e98e708dabd4580bb591.gif

There was a mid-late 90s Oldsmobile that was notorious for this. You could explain it ahead of time to customers and they'd still rant and rave if it happened. It always resulted in us uninstalling the equipment. I wonder how stupid they felt when it returned to normal in a couple days like we said and they didn't have anything to show for the experience?

 

[Louisiana_CRX 5,000+ posts]

lesson learned : Don't unhook the battery when hooking up a new car stereo.....