SRS problem, RF tensioner signal too low?
 

I've been working on my friend's 2004 XC90 that displays Supplemental Restraint System Service Urgent message on instrument cluster and red air bag light on. I pulled codes from the SRS computer and they were: "SRS-0069: Front Right Seat Belt Tensioner Signal Too Low", and "SRS-010C: Front Right Seat Belt Tensioner Circuit Fault." The original scan tool I used was a Launch (not VIDA) and the description it gave for the SRS-010C code was "Control Module. Internal Fault."

My friend described how the light came on. While driving, with her brother in the passenger seat, he repeatedly pulled on and locked the seat belt to try and turn around to play with someone in the back, and the light came on.

Having quite a bit of automotive and electrical experience, I presumed that the cause of the problem was in the seat belt tensioner, which is located in the B-Pillar and part of the the seat belt retractor. After replacing the tensioner, the same codes codes were present and would not clear. Also, the old tensioner was tested using a long skewer and was determined not have deployed, and there was 0-0.9 ohms resistance across the contacts, indicating good conductivity.

Flustered, I recommended that she take the car into a Volvo dealer. After two weeks of fault tracing the RF tensioner circuit, the dealer concluded the problem was in the wiring connector at the tensioner. Apparently, there is some built in capacitance/resistance to this connector. The dealer wanted $4,000 to replace the entire SRS harness, saying that a new connector was not an option. I ordered a connector pigtail from the junkyard, installed by cutting and splicing the wire using solder, and scanned the computer again. This time, the codes were the same two as before, plus two new codes:
SRS-0069
SRS-010C
SRS-006C "Front Right Seat-Belt Tensioner: Resistance too high."
SRS-0044 "Right Front side impact protection (SIPS) bag, Resistance too high."

The next thing I am going to try is shortening the wires and/or using a butt connector instead of solder to splice the wires, to try to reduce resistance. Does anyone have any familiarity with this problem? I find it hard to believe that the original two codes would still exist if the connector was really the problem, although it is possible. The dealer refused to perform the SRS module software update per my request, saying that it was not necessary. I now wonder if a static charge from the kid pulling the seat belt repeatedly may have fried the module, or the module may have a counter which trips the light after a certain number of faults. I'll keep posting the updates, thanks in advance, Joe.

2004 XC90 2.5

Ok so I removed the solder joints on the new connector and replaced with butt connectors and slightly shortened the wires. In the next couple days I'll figure out if there's still codes in the computer for excessive resistance.

I took the old connector apart and found what appear to be two capacitors inside it. The larger capacitor, which is placed in series in the green/orange circuit, measured out at .456 microfarads, and shows resistance increasing to infinity when tested with an ohmmeter. The smaller capacitor is .01 microfarads and is in parallel with the green/orange and orange wires. It shows infinite resistance until tested at 2000 mega ohm setting where it briefly flashes about 850 megohms of resistance then goes to infinity as well.

Does anybody know what these values are supposed to be or how they are supposed to behave?

I hate to say it, but I don't think you will find much info on this, considering Volvo does no have any published specs for things like this. They don't sell the connectors or have any repair procedures for SRS wiring- there is too much liability there.

Is it safe to drive a car with the SRS warning light on?

SRS warning
 

I would like to know as well...but I suspect that the SRS system may be inoperative when the SRS message is present. It seems that nobody knows the answer to that question.

When the light is on, the system may not work if needed.