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-   -   SRS Light on: how would you diagnose (2nd of 2 lights on my son's D2) (https://landroverforums.com/forum/discovery-ii-18/srs-light-how-would-you-diagnose-2nd-2-lights-my-sons-d2-92586/)

mln01 12-18-2018 06:34 PM

Yes, that's correct. I am very sorry I left out the part. I tested continuity in each wire of the circuit separately with the airbag removed and out of the car.

You should always disconnect the battery and let the car sit for at least 10 minutes before touching the SRS circuitry.

And to answer the OP's question, the SRS system circuits all go to a special "computer" module located underneath the rear of the console called the DCU (Diagnostic and Control Unit). It is a standalone system with no interfaces to the ECU, BCU, SLABS or any other computer systems. I'm not in a place to confirm the facts right now, but I recall it has a decelerometer built into it, so that when it detects very rapid deceleration it deploys the airbags and pretensioners. It was the connector to the DCU that had a short in it on my truck.

Again, the Restraint Systems section of the RAVE is your friend! You could've found all this information there.

austinlandroverbill 12-28-2018 09:49 AM

D2's been sitting, so walked away from this for a while.

Put OBDII reader on again and message was:

"open circuit fault driver airbag circuit"

so it is definitely the driver airbag, which I am guessing means either:

1) the airbag itself
2) the rotary collar
3) the wiring from the collar to the DCU "special controller" at the back of the console
4) the "special controller" itself

I am assuming that I would've gotten a different message if it was the airbag or the DCU SRS controller, so for now I'm going with 2 or 3, the rotary collar or the wiring from the collar to the DCU buried in the console.

Will finally look at the restraint system section of the RAV, but in the meantime can mln01 or anyone else give me some idea of how hard (scale of 1-5) it is to access that DCU and the corresponding plug from the rotary collar buried in the back of the console as I have never had the console off before?

I am worried I am starting to lose my discipline and am just going and buy a rotary collar off of eBay for $40 as it seems a lot easier to replace that and see if that fixes it before diving into the console, which seems a lot more involved an effort. My only trepidation about doing this would be that I would be assuming that only the airbag circuit thru the rotary collar has failed as all the other circuits thru the rotary collar -- horn, volume, cruise -- seem to be OK.

Am I lazy or what . . .

mln01 12-28-2018 02:18 PM

Bill,

Well, it's not looking like "or what." ;)

Let me add a 5) to your list; the DCU connector itself. Again, in the case of my truck it was a short in the connector that triggered the SRS light.

Like anything, removing the console can be intimidating the first time you do it, and I admit I used to look at it as a big PIA, but just get on with it. The console itself is no big deal but disconnecting the seat switches can be a pain. Look for YouTube vids for help.

There is only one connector for the DCU, which has all the wires from all the SRS components (two airbags (two wires each), two pre-tensioners (two wires each), diagnostic feed, instrument pack light, ignition switch supply and earth). In addition to the RAVE DII Workshop Manual you should have the DII Electrical Library and the DII Electrical Circuits PDFs. The DCU connector is C0256.

austinlandroverbill 12-29-2018 11:33 PM

wow, tough love.

didn't even think about the seat switches. Ugh.

I have a RAV and the engine rebuild guide, but not the DII Electrical Library and the DII Electrical Circuits PDFs. Where can I download those?

mln01 12-30-2018 09:01 AM

Try a Google search or two.


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