[V8] ECU grounding, etc. (abridged)

Coleman, David David.Coleman at blackrock.com
Tue Oct 11 15:29:06 EDT 2005

So THOSE are the Kostal Connectors... I see, said the blind carpenter,
as he picked up his hammer and saw.

The Kostal that the ECU's #54 brown wire leads to is #11 ("Motronic to
Automatic Transmission").  So I can see why I would have a dead end
there (though I gotta wonder why it's not a similar situation w/ #s 12
and 14 (Instrument panel to auto trans, engine compartment to auto

Crap.  Or good.  Either way, the lack of ground at the ecu harness #54
is expainable.

I guess it's on to figuring out why the MAF test requirement for 19-37
continuity ain't there, and from there to the TPS, and then to the
crusher.  Just kidding -- I won't check the TPS.


> So ECU terminal 54 still has no good ground as stipulated in 
> the manual, and jumping it to ground makes no difference in 
> the running condition.  As Jeremy pointed out, the wiring 
> diagram does indeed indicate that 54 seems to jumper off 19:
> http://www.sjmautotechnik.com/trouble_shooting/v8_pinout.html 
> And no, I don't have continuity between the two at the 
> connector (good ground at 19).  The thing is, when I trace 
> the brown #54 wire from the ecu harness connector, it runs up 
> the loom and splits off among a small cluster of other wires 
> and leads to the first of five black plastic harness 
> connector boxes mounted to the firewall behind the ECU mounting area.
> And the thing after that is, whatever these black boxes are 
> (each about the size of a thumb, mounted parallel to one 
> another), all but the one that the #54 brown wire cluster 
> goes to have two halves, sandwiching an in-cluster and 
> out-cluster.  The first one has no other half, i.e. it's a 
> dead end.  WTF?
> Could this connector box be for automatic transmission 
> controls?  If so that might render terminal 54 as not 
> requiring a ground if the car's a manual trans...(?)
> Thanks for any thoughts!
> DaveC.
> > + Car starts only after a few 1-second cranking sessions.  
> Won't start
> > w/ extended cranking.
> > + Once warm, idle begins to fluctuate wildly (0-1500 rpm) 
> until engine
> > dies
> > + Engine will immediately bog down trying to kill the motor if
> > anything close to WOT, either revving or driving.
> > + Car runs WAY too rich, in all running/driving circumstances
> > I've replaced the FPR and spark plugs.  From there:
> > + Code consistently shows 2324 (bad ECU ground, MAF wiring)
> > + Running diagostic output tests indicate all injectors click, ISV
> > actuates, but carbon canister solenoid no good
> > + Replaced canister solenoid and associated vac hose clamps,
> > now clicks away during output tests.
> > Checked ECU:  
> > + ECU voltage supply check asks to confirm ground at 
> terminals 10, 14,
> > 19, 24, and 54 of the harness connector ---  All were good 
> except at 
> > 54.
> > + I also picked back up on the MAF sensor check procedure, which was
> > asking to verify continuity between ECU harness connector pins 19 & 
> > 37.
> > No good.  Blames an apparent short between ecu pin 37 and 
> terminal #5 
> > of the MAF sensor connector.  So far no luck finding a short...
> > So the upshot is: how does terminal #54 of the ecu harness 
> connector 
> > get its ground?  Any other thoughts?
> > 
> > Delirious in Delaware,
> > 
> > DaveC.
> > '91 V8 5-speed

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