I do not know much about the inside of an ECU but here is the situation:

Just tried to start the car and the ECU started smoking. Popped the ECU cover and the transistor labeled Q31 is fried.

Before starting the car I had just wired in a 4 wire O2 sensor. I searched the archives on how to do this correctly and double checked everything. Motor is a b16A2 in a 92 CX (OBD1). I never had this problem until today - the car had been started previously. I had an extra ECU laying around so I unplugged the O2 sensor, and the same thing happened again.

Any help would be appreciated.
Thanks




Modified by theneil at 7:29 PM 3/5/2006

 

bump

 

you have the purge control solinoid and IAT plugs switched.
it causes Q31 to pop in a few seconds.
Replace Q31 and switch the plugs and you should be fine.

 

Thanks for the info

Could someone please open their ECU and read the small id number on the black rectangular transistor labeled Q31 (it is close to the plugs on the harness) I would like to order some but I can't see what the numbers are because they are fried.

Thanks again for the help


Modified by theneil at 7:00 AM 3/7/2006

 

bump

 

bump, need the number on the transistor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by theneil &raquo;</TD></TR><TR><TD CLASS="quote">bump, need the number on the transistor</TD></TR></TABLE>

D1780, and they have been obsolete for years.

 

according to a post on PGMFI.org

go to digikey.com
search for 2SD21780RACT-ND
$0.83 each. + $5 S&H grumble....

I use ones out of ECUs I have parted out so I'm not 100% sure if that's the right part.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Relic1 &raquo;</TD></TR><TR><TD CLASS="quote">according to a post on PGMFI.org

go to digikey.com
search for 2SD21780RACT-ND
$0.83 each. + $5 S&H grumble....

I use ones out of ECUs I have parted out so I'm not 100% sure if that's the right part.</TD></TR></TABLE>

I don't agree with that as a replacement. The D1780 is specifically designed to be directly driven by the IC without a intermediate driver transistor. I would be concerned about the load the 2SD21780 would place on the IC and potentially overload it's output. The two parts are electrically different as well.

.pdf for the 2SD21780: http://www.semicon.panasonic.c...D.pdf

.pdf for the D1780: http://www.pgmfi.org/twiki/pub...0.pdf

theneil,

What is the full part# of your ECU? Depending on the board # you might be able to pull one from another location, and swap in a common replacement part.

 

Thanks for all the help