SRS Control Unit fault, 2000 VNL770

My new-to-me 2000 VNL770 came with an SRS (air bag) fault showing on the graphic display. The fault code is MID 232 SID 254 FMI 12, which translates to a fault in the Control Unit. The fault was Active.
I found a "used" control unit, #3172088, on Ebay for $75 and gave it a shot. The local dealer wanted over $2000 for a new Volvo part.
After installing the Ebay used Control Unit, the diagnostic output shows the fault as Inactive. However, after inputting the password (1234) and doing "Reset All", the fault continues to show up as Inactive, rather than simply going away.
When viewing the fault, I can press "down" and it shows "Reset All" as if that were an earlier fault in the list of recent faults. This behavior is NOT described in the service manual, which I have a copy of. According to the manual, the fault should go away when the Control Unit is replaced.
So on the one hand I'm tempted to return the Ebay module as DOA, and get my $75 back, but I'm also suspicious that there may be something else wrong.
Can anyone help me understand what might be going on here?
If the Ebay part is indeed DOA, are there any other sources for a new part that would be much less expensive than my dealer's price for the Volvo part? Am I wasting time if I look for a used one out of a wrecked truck?
Finally, would it be sensible to just ignore the error and hope the air bag would work anyway in a crash, or to just drive without an active SRS?

For reference, the truck has about 900K miles, was originally part of a fleet (US Express, I think?), there have been two owners before me, after the fleet sold it, the engine is Detroit S60 12.7L, tranny is 10-sp autoshift. There are no other faults; all other subsystems show "No faults".

Pete

 

Hi bonous,

I ended up returning the Ebay controller as it definitely appeared not to work.
To this date I have still not fixed the bad SRS controller. Every time I start the truck the airbag error appears, but I just dismiss it using "Escape". I've looked for a good used controller on and off, with no luck yet. The new part from Volvo costs about $2300 and there are 5 showing in the US. I keep hoping I can find a used one from a totaled truck for under $200!

Your error is different however, since your SRS controller is reporting an active ignition loop fault. That involves the resistance of the ignitor being correct. I suspect you have a corroded or open connection somewhere near the airbag in the center of the steering wheel. The Volvo service manual has a procedure for checking the airbag ignitor circuit. You must be very careful to do this right, to avoid accidently igniting the explosive charge!!!

Good luck solving your electrical issue.
Pete