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DISCUSSION => Electrical => Topic started by: SpecFC on December 08, 2011, 08:54:43 PM

Title: HELP! ECM getting hot to the touch!
Post by: SpecFC on December 08, 2011, 08:54:43 PM

Hopefully someone can offer some insight here, I've been searching for two days now trying to find a clue as to what's going on here...

The car is a 1991 318is, was in poor, but running condition. parked it, installed mark d chip. Try to start, nothing. Go to replace possibly fried ECM with known good, and stock chipped ECM and discover the ECM is HOT to the touch, even with the key off and out. Baffled, install the stock and known operating ECM in, and it starts getting hot. WTF is going on?

Title: HELP! ECM getting hot to the touch!
Post by: Geoff on December 09, 2011, 05:57:24 AM

that is a weird one.  did you disconnect the battery when R&R  ing these ECU units?   I've been told they can fry if you dont.
                                                                   Geoff

Title: HELP! ECM getting hot to the touch!
Post by: DesktopDave on December 09, 2011, 06:58:57 AM

That is a weird one.  I'd be testing the power harness to see if anything is shorted out.  IIRC there's only one wire that should be hot all the time.  If it's hot all the time I'd suspect a short in the supply harness first.

Have a copy of the electrical troubleshooting manual?  
http://wedophones.com/BMWManualsLead.htm
I usually use the 1991 325i as the 318 is missing a few pages.

Title: HELP! ECM getting hot to the touch!
Post by: SpecFC on December 12, 2011, 07:52:55 PM

Pulled the ECM off and checked all the pins on the wiring harness side. Results as follows:

Pins 1, 3, 26, 27, 29, 32, 36, 37, and 54 had anywhere from .11V to .26V

The remaining pins all had 0V

Lack of constant power and the small voltage is leading me to think the constant 12V is shorting to ground somewhere...