SIR secondary ground

[CamP]

Does anyone know where the secondary ground for the SIR is located on the 1990?

TIA

[tomtom72]

I think you're having the "INFLREST" and "SEATBELT" trouble lights on your DIC?

If so, the issue is at the two impact sensors located on the frame rails, left & right front. The right sensor is near the washer bottle, if you take off the rear most inner wheel house panel you can just see it. The left sensor is located just ahead of the front inner corner of the battery, and you could just take out the battery or perhaps remove that side rear inner wheel house panel. I took the battery out.

The problem is that the sensors are grounded via their mounting tabs to the frame. The frame is painted, and they get a fair amount of moisture on the mounting ears to cause some minor corrosion to degrade the ground connection. Just remove the sensors and clean everything up and remount after using some dielectric grease. Then you have to clear the SIR codes.

:cheers:
Tom

[CamP]

Thanks Tom, I'm aware of the grounding issues with the sensors, but I seem to recall Gordon Killebrew mentioning a secondary ground that was only used in 1990 being a source of code 16 faults.

[scottfab]

Thanks Tom, I'm aware of the grounding issues with the sensors, but I seem to recall Gordon Killebrew mentioning a secondary ground that was only used in 1990 being a source of code 16 faults.

I am not aware of any SIR problems brought on by a secondary ground.
All I've seen on my 90 have been the related to the threading on the ground bolts to the frame on the two sensors. They rust.
Grinding the paint away makes for a better ground and seems to have solved my SIR problem for over 10yrs now.
There is also an issue with the gold connectors on the yellow colored wires that come from the sensors on the inside of the firewall. You might want to unplug theses, clean and apply dielectric grease also.

[tomtom72]

Thanks Tom, I'm aware of the grounding issues with the sensors, but I seem to recall Gordon Killebrew mentioning a secondary ground that was only used in 1990 being a source of code 16 faults.

You're welcome! The service bulletin 90-401-9 which applies to all C4's besides ZR-1's. was issued in 1991. The only thing I remember was to do a Scott Fabre suggests and use a star washer to get a better ground from the mounting tab. There are no other grounds save the mounting tabs and the grounds that exist in the actual SIR system wiring harness.

If you are having the code 16, you need to repair the bad contact at the sensor ( both L & R ) mounting tab. That's all there is to it besides clearing the codes which will take some patience.

:cheers:
Tom

[Hoekie]

I actually did this job last weekend, ie to remove both sensors and clean the frame and sensor tabs.
What I did find is on th battery side there were 2 additional earth wires, one comes directly from the bat negative terminal and the other Im not quite sure but it is one of those thin braded cables. Both these are also fixed to the rail at the sensor.
Unfortunately I cant say if my problems are solved because Im waiting for my speaker amps, so the seats are out and part of the dash is still stripped.
Maybe this is the additional earth you are trying to find?
I have a 1990 so should be the same :cry:

[scottfab]

I did this repair a decade or so ago. Here is a pic of the one near the battery. Note the battery/frame ground is separate.
If this ground goes south starting would be difficult.


http://www.zr1netregistry.com/Old_Proj/MVC-043F.JPG

The whole series of "How to" do this fix is at:
http://www.zr1netregistry.com/Old_Proj/old_proj7.htm

[CamP]

I did the old sensor ground routine and the code cleared. Surprisingly, all the grounds looked fine and there was no corrosion to speak of, but pulling everything apart and cleaning the surfaces up a bit seems to have done the trick.

[scottfab]

I did the old sensor ground routine and the code cleared. Surprisingly, all the grounds looked fine and there was no corrosion to speak of, but pulling everything apart and cleaning the surfaces up a bit seems to have done the trick.

Good to hear. Should it come back later I suppose you'll do the full
routine.

[CamP]

Good to hear. Should it come back later I suppose you'll do the full
routine.

I went through it once about 15 years ago. Hopefully it won't come back for another 15. ;)