NA6 SRS system code 4

[sharkythesharkdogg]

1991 BRG with a code four, or S-Sensor code. So far the wiring harness testing all checks out, and it's pointing me towards the actual sensor. Unfortunately this is the sensor located over the air handler box under the dash. So before I start pulling apart this almost immaculate 23k BRG I decided to go ahead and check the main board in the ABS computer.

The main board looks good around the capacitors to me. I checked it under a black light because I've heard you can occasionally find signs of leaking that way, but the board still looked good.

Anyone with more circuit board experience notice anything out of the ordinary on this one?

One last chance before I go trying to carefully remove 25 year old plastic bits.

[miatastuff]

Can you test the resistance values for the sensor at the airbag controller? Or swap in a known good controller to test!

[sharkythesharkdogg]

I suppose that means the board looks good visually to you too?

I'm not sure what that resistance value should be, do you know? The manual says to simply check for continuity between terminals B and E of the sensor itself. Continuity means the sensor is good, and no continuity means replace the sensor.

Even getting access to the plug sucks though. I can barely get my hand on it, but I haven't been able to get the plug to release. Undoing that safety style SRS plug when it's stuffed up under the dash behind an air duct has proven very hard. I didn't want to test the terminals through the other side of the harness because it doesn't eliminate a possible bad harness from the testing.

I'm digging around for another good air bag computer, so I'll try that first.

[sharkythesharkdogg]

I found a good computer in my pile of bad ones. I have one more good one left. Any one know of any good guides on repairing these things based on their related codes? Good ones are only going to get harder to come by.

I'm going to test it a little more, but so far it looks like the AB computer. It's almost always the computer it seems. I think I've replaced a sensor twice out of all the times I've run the diagnostic process on these situations.

[iscariot]

C7 looks like it's slightly bulging. But that said, I'd replace all the caps because they're cheap and 20 years old and electrolytic caps are more or less a wear item.

https://forum.miata.net/vb/showthread.php?t=137880 appears to agree.

[sharkythesharkdogg]

It might be, but I think it's more the picture. If this other computer keeps working then I'll probably replace all the caps in this one anyway. I'm just curious if there's a guide out there where someone smarter than me has taken the time to figure out these old Ford modules. Specifically, "this code means check these specific components."

I might just replace the caps on all these old boards and see what I get. I also just might start telling people to run Grant wheels and be done with it. :dunno:

[tbone heller]

Mine used to give all kinds of codes until I had the windshield resealed.