[s-cars] Bad ground connection

[racingiron at comcast.net]

Wayne Dohnal wrote: 
> I'm chasing an engine problem and it looks like one of my ground 
> lines isn't grounded. It's ground #201 and goes to the ECM, ECT 
> sensor, TPS, atmospheric pressure sensor, and knock sensors. 
> The ground lines at the sensors are connected to each other, but 
> not to ground. All I can find in the Bentley is that it's ground 
> connection 5 in the engine wiring harness. I've found 6 ground 
> wires bolted to the intake manifold and they're all ok. Does 
> anybody know where the ground connection 201 is actually 
> connected to ground? 

I followed that wild goose chase a while back when searching for an engine cutout problem. Bentley is misleading here. It appears that it's saying there is a ground point (#201 or connection 5) where all that stuff is connected. I discovered (on my '92 at least) that must simply be a point in the harness where all those wires come together. The wire from pin #30 on the ECU doesn't go out to a ground point, it PROVIDES the ground for all those other wires back through the ECU. With my ECU plugged into the harness, I had continuity to ground at all those sensors--unplug the ECU and that connection went away. If you're not getting a connection to ground with the ECU plugged in, then check the wire at pin #24 that goes to the manifold. I'm not positive, but that's probably where the ECU feeds pin 30 back to ground. If that wire is OK then maybe you've got a bad connection inside the ECU? 

HTH, 
Eric R. 
'86 urq 
'92 urS 
'93 urS