electrical issue - dash lights etc failed after long trip

[dwd]

Just back from a 12 or so hour drive from NYC back home to North Carolina, first long trip in a recently-acquired 2004 XC70. Car drove great the entire time, and it got what I consider to be good gas mileage for this car. No problems - until just now in our driveway back home.

The last leg of the trip was about 4 hours of driving straight through. When we got back home and were unloading I noticed the hatch light didn't come on when opening the hatchback. Tried locking and unlocking the car from the key-fob and oddly that didn't work - pressing the key unlock button turned on the front interior lights, pressing the lock button turned them off, but the buttons didn't actually lock or unlock the car. The interior front floor lights were on throughout this, though. So, we tried starting the car, and with the car started, none of the dash lights came on. The headlights came on but I couldn't turn them off / switch to parking lights, and I couldn't turn on the bright lights / high-beams or the fog lights. And there was an error message saying "SRS Airbag Service Urgent".

Turned the car off and checked the fuses and everything seemed fine there. With the car off, those floor lights were staying on, so I decided to deal with this tomorrow, and to keep the battery from draining I thought I would disconnect it. I went into the cargo area and disconnected the negative terminal of the battery, then just on a whim, re-connected the terminal to try things out one more time. And now everything is working. All interior lights work as expected, key fob locks/unlocks the doors, etc. Only remaining issue is the "SRS Airbag Service Urgent" message still displaying.

Any idea what might be going on, or anything I could/should check into to try to find out what happened? We've had this car about six months now and not had any electrical issues at all, and had no problems on this extended trip.

I've read through some of the posts about electrical gremlins on this site, but haven't come across a situation quite like this one, but let me know if I missed a relevant thread...

Thank you...

[jimmy57]

You were seeing symptoms of the low speed electrical network being offline. The battery disconnect reset the control units but the airbag/belt system does not clear its codes automatically on Volvos. Once an SRS trouble code is registered it has to be read and cleared with diagnostic equipment with those capabilities. The codes in other systems on the low speed network could still be in those systems and some of the codes could be very specific as to the cause.
Volvo dealer visit should answer a lot of questions.

[Hans]

Wife just home with all DWD's symptoms. Found both battery terminals with very heavy buildup of "white" powder. Same cleaned and after alarm reset all working well. Also had Engine light (yellow) illuminated. Now need to get SRS light cleared.
Thanks jimmy57 for info.

Regards
Hans Johannesburg area

2001 V70 XC
2004 XC70
2004 S60R