[Diy_efi] Grounding issues with Honda ECU

[Peter Vieth]

         Hey everyone, I've posted here before about o2 sensors troubles, 
but since then I've worked out some mechanical issues that were getting in 
the way.  I've got a '86 Acura Legend that has been having intermittent 
problems with the ECU setting o2 sensor codes for two years.  The o2 
sensors are good (replaced em twice, they are the 1 wire kind btw); when I 
got the car however the wire to one sensor was bad. I finally got around to 
a permanent fix for this, checked that the o2 sensor behavior was good, but 
the ECU still set codes for the o2 sensors.  While going through the 
troubleshooting flowchart in the manual, I noticed that the gnd wire going 
into the ECU is at approximately -.20v to the ECU body and body of the car 
at idle.  This seems to vary somewhat, as each time I hooked up my DMM it 
was slightly different.  With the DMM hooked up to an o2 sensor and the gnd 
wire, the o2 sensor voltage varies from -.50v to +.60v, and it is 
'backwards' in that it idles at anywhere from +.30v to +.70v and at 4000rpm 
is at -.50v.  With the DMM grounded with the car chassis the o2 sensor 
behaves normally, +.80v at 4000rpm and average of +.55v at idle.
         The question is what to do about this.  I could wire the GND wire 
to the car body under the ECU, but I wonder if there could be some reason 
not to do this.  The EFI schematic shows two ground points, but does not 
say where they are located physically on the car.  Has anyone out there 
maybe got some advice?



Peter Vieth <fitek at ix.netcom.com>
http://www.keast.com/slugman


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi