2004 V-70 AWD has an unintended downshift at highway speed. Occurs mostly in wet weather after sustained (3 hours) of driving. Occurance is a loud drivetrain BANG, momentary deceleration, and RPM needle jumps about 500/1000 RPM. Duration of event is less than 1 second and transmission reverts to 5th gear. Information display says LEFT REAR PASSENGER DOOR OPEN, followed by SRS AIRBAG NEEDS SERVICE, followed by ABS BRAKE FAILURE STOP SAFELY. Event will re-occur within 3 to 5 miles. Stopping and shutting off engine resets whatever the cause was and leaves the SRS AIRBAG NEEDS SERVICE on the info display. Message cannot be cleared. Diagnostics (3 times) show nothing.
First event at 88,300. Has occured 3 more times after that about every 3000 miles under the same conditions. V70 has been same dealer serviced since new. Nothing has been neglected that needed repair or replacement including a $1,200 instrument cluster replacement at 94K. The 3rd event was able to get the car diagnosed before the engine was turned off. It was referred to by the Volvo dealer as and active event. DCM also failed at that time. They just shrug their shoulders when they haven't found the cause.
Dave R

 

You could have had the DIM repaired by Xemodex for about $150. For the trans maybe a flush or replace the B4 servo cover?

 

Given the wide range of systems that are affected, I'd guess that you're looking at an electrical or computer fault... maybe a bad ground? I'd suggest looking over a wiring diagram for your car to see what's common to the transmission, brake and air bag controllers. I can sympathize with the dealership though - there's nothing harder to fix than a problem that won't show up.

 

happyguy,

Thank you for the response to the post. Turns out it is not a transmission downshift. It is a momentary engine shutoff and restart.....probably about 10 milliseconds.
It has occurred 7 times since 2010 (88K miles). The results are multiple sequential failures throughout the electronics system. The local Volvo dealer has seen it before and has named it "nubbling", a series of system failures after the initial fault. They have been unable to diagnose the problem. They claim it has to be active in order to get better readings. Shutting off the ignition resets everything except the third fault condition...SRS Air Bag Needs Service Urgent. The systems that sequentially fail are as follows: Event occurs at any speed. Highway speeds result in a drive-train jolt that feels like a downshift from 5th to 2nd. Below 30 its just a little jerk to the momentum.

The first error message is: Left Rear Passenger Door Open (its not). The Second event (about 2 minutes later) message is: ABS Brake Failure, Stop Safely. The third event message in another 2 minutes is: SRS Airbag Failure Urgent Service.

Then the following happens if the car has not been stopped and shut off. DIM (instrument cluster) goes off with no lit or functional dials. AC stops working, Fan remains on but is not re-settable. Window regulators stop functioning, Emergency flashers will not work, windshield wipers (if on) will not change speed, low speed power steering boost will not function, turn signals will not work. Transmission defaults to 5th gear (winter mode?).

I have not checked some of the other functions like the power seats or sunroof but have stopped the car to see if the headlights and running lights are functioning. They have on the only event occasion I had the opportunity to check before shutting the engine off.

Damage and repair history:

60K miles water was spilled on the console (winter) and froze the electric actuation for the shifter. Disassembled and dried out by the dealer.
75K miles required a new (coded key) ignition system as the original fell apart.
85K miles ran over a truck tire carcass at 65 mph in torrential rain. First event followed within 200 miles. It was not diagnosable and code was reset.
88 K miles event occurred when caught in an interstate traffic accident slowdown. DIM failed. ABS failure message.
88.4 K miles event occurred again.. Same messages...Same result.
92 K miles event occurred after driving in rain for 1-1/2 hours. Arrived at Volvo dealer with active event and they said the computer was having a seizure and would not read out. Reset the info display after shutting down the engine.
95 K miles event occurred after engine had been idling in hot weather in a parking lot for 10 minutes.
106 K miles. After 1 hour highway speeds in a thick misty rain.
100 K miles 3 hours highway driving in heavy rain and after it had stopped raining.
110 K miles 30 minutes in local traffic, dry cool weather, accelerating from a traffic light.
went to Volvo dealer and had it diagnosed. Have a long involved printout and not solution.

Have some theories but they involve guessing what to attack first.

Dave.......Love the car....frustrated with the manufacturer and the dealer.

 

The (almost) common thread through this drama seems to be moisture. I'm guessing that you're dealing with a moisture-contaminated connection somewhere, and that it's creating a low-resistance short between two (or more) connections somewhere in the electrical system in your car. If it was just a corroded or loose connection, I'd guess that it would be a LOT easier to find, and that it wouldn't create such total havoc through all those disparate systems.

The two places I'd be most suspicious of would be the area where you spilled water on the console (the reason I really hate dash-mounted cup holders - I had a HUGE amount of work on a Jetta wagon I re-hab'd because the previous owner had apparently put a few gallons of Coke into the shifter and console over the years), and the ignition system that the dealer repaired.

The difficulty in all this would be getting TO the problem areas, of course... the "fix" would be to remove the plugs, spray them with electronics cleaner, and scrubbing them to remove any "growth" between the contacts / wires. Of course, by the time you get to the connectors, you'll have the car torn down pretty far.

There's also a possibility that you're dealing with the effects of a stray drop or two of water that got into one of the (many) computer modules. When that happens, a "dendritic growth" can happen between two or more of the tiny little connections on the printed circuit board (most often around the microprocessors, since the connections are smaller and closer together, and the effects of a low-impedance short there is the most dramatic). I'm not really sure which one would have gotten wet with your beverages mishap, but that's where I'd start.

I can sympathize with the dealer though - finding a problem like this is very close to impossible if it's not failing when they have it (and in a case like this, maybe even then). And of course, even if you were to take apart the console and dash and clean up every connector, and maybe even replace any potentially bad module you won't know if you've done any good until it fails again (and then you'll know you DIDN'T fix anything).

Good luck with this one - an intermittent problem that goes months between occurrences can be one of the most frustrating things you'll ever deal with (particularly if you're paying dealership labor prices for any repair attempts).

 

DING DING DING!!!

Running over the tire carcass may have caused all this grief. It's possible some wiring has been damaged .Also, A connector or 2 may have been loosened or damaged.

Has the car been put on the hoist and checked for this? If not you may consider having the underside inspected.

Good Luck