Do I Really need a new ECU? - GreenHybrid - Hybrid Cars

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Old 03-13-2013, 09:16 AM
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Join Date: Aug 2007
Posts: 6
Default Do I Really need a new ECU?

06 civic Hybrid 133k miles. Stopped at gas station to get gas turned engine off to pump. All gassed up turn engine on and the IMA, CEL and Brake System Failure lights all come on. Couldn't take car out of park (safety mechanism i assume) and engine rumbles and stalls. Wait 20 mins, started car again - this time only CEL is on - no rumble no stall - I drive car to dealer. They pulled 4 codes all having to do PCM and IMA. They do a PCM update and call to say car is fine and ready to pick up. I come to pick up, and CEL is on again - they pull 2 new codes having to do with the "motor assist module" and the "battery? assist module". Leave the car again, now saying car needs a needs a new computer ~$900. I cant find anyone with a similar problem online. Could there be an alternative issue like loose wire or connection?

Might there have been issues I could point to while the car was still under warranty like an oddly inconsistent idle (idle would pulse between maybe 300rpm and 1000). This is also what it was doing when stalling out at the gas station.

Thanks in advance for any input.

Last edited by konrod; 03-13-2013 at 09:19 AM.
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Old 06-26-2017, 12:15 PM
Join Date: Feb 2008
Location: Switzerland - swiss alps
Posts: 7
Default Re: Do I Really need a new ECU?

I have exactly the same problem!
Did replacing the ECU solve the problem?
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Old 07-10-2017, 10:17 AM
Join Date: Jul 2017
Posts: 1
Post Re: Do I Really need a new ECU?

I suspect that a new ECU might be the answer. It is an expensive solution, so I would really appreciate some feedback on the following.

I have similar symptoms (specifically in hot weather). Dealer said IMA Batteries: I replaced them - no change. I replaced the whole IPU control pack and the IPU cooling fan (since it was "heat induced"). No change.

Specifically my full symptoms are:

1. Starts to “jump gear” momentarily as though it is being slipped into neutral and immediately back into drive. As it does this, gear selection indicator on the gear shift showing the lighted “D” will flash off and on synchronized with the “slipping”.

2. After 30 seconds or so, it goes permanently into “near neutral”, gear indicator lights stay off permanently, speedometer reads zero, average mpg reads “----“ and the brake fault light comes.

3. Another 30 seconds or so, electric steering fault light comes on. At all times brake and steering are fine.
Moving the gear shift up and down between Low and Drive has no effect, but moving into neutral changes it from “near neutral” to 100% neutral. (“Near neutral” means that it feels like neutral but will get up to 30 mph very slowly as long as the incline is less than 10%.)

4. Another 30 seconds IMA warning light comes on.

5. Eventually, engine stalls. If you put it in park at this point, it will not come out of park whatever you do.

6. Wait 5 minutes or so (in shade - until sun goes down in sun) and everything goes back to normal. Drive a mile and symptoms return, but progress more quickly this time. Wait 10 minutes and it will probably take 2 miles to goes haywire again. Wait until the car has fully cooled down and it quite likely will not happen again until you get back into slow moving traffic under a hot sun.

The "gradual systems close down" symptoms (especially if heat induced) would definitely indicate failure of the main electronic control unit, but dealer took me down the wrong path by saying that the diagnostics indicated that this was caused by the IPU system forcing such a low voltage (8V they said) on the 12V system, that it was bringing thge voltage down too low for the ECU to function properly.

I am now (after wasting a lot of money, but learning a lot about hybrids) forced to conclude that it is failure of the ECU that is bringing down the whole system.

ANyone have experience to support this?
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Old 07-10-2017, 02:13 PM
Join Date: Feb 2008
Location: Switzerland - swiss alps
Posts: 7
Default Re: Do I Really need a new ECU?

Quick update on my problem:
I replaced the ECU with one from a crashed car last week. Until now, the car is running perfectly.

I had similar problems:
- When the engine was cold, I NEVER had a problem.
- I NEVER had a problem as long as the engine was running, and I didn't turn off the car (auto stop was working fine).
- When the engine (and the weather) was hot, I had often a problem turning on the engine after it was running. A lot of errorcodes where showing up (on my scangauge). One of them was "low voltage...?!", another one was "communication error on the CAN bus"...?!. Sometimes even the IMA light came on.
I was still able to turn on the engine (sounded a bit strange sometimes), but I was always unable to move the gearshifter.
- Sometimes, disconnecting the 12v batter helpt. Sometimes I had to wait for hours to let the car cool down.

After replacing the ECU with a used one, the software needs to be updated and it needs to be ajusted, so it works with the existing keys (according to my Honda dealer, the Honda diagnostic device needs to be online to do this, my dealer was struggling with that.....)

If someone is intrested, I think I have pictures of the errorcodes...

Last edited by Lori; 07-10-2017 at 02:17 PM.
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