P2 2001 V70 T5 Sudden Massive Electrical Failure

[Brickbat]

OK, well I'm not going to be the noob that pops in with a problem, and never closes out the thread.

But, I really don't have a resolution yet.

Here's the entire mini-series:

Summary:
The car has had three occurrences of sudden electrical failure over the last month. These three instances were similar, but each a little different.

History:
I’ve had the car for about 5 years, drive it almost daily and prior to this have had no issues like this. The last item to be repaired that might be related was the alternator. Oddly, after I replaced the T belt, tensioners, and camshaft seals last winter, the alternator was dead. I put in a new (but crazy cheap) eBay alternator. That was almost a year ago. It’s been throwing occasional Cat converter or O2 sensor codes for as long as I’ve had it, and recently threw a low coolant temp code.

1st Failure
The first electrical failure happened about 30 days ago. As I exited the highway, I noticed the instrument cluster gauges went to zero. I don’t recall any idiot lights, but I’m not sure about that. The engine wasn’t running. I coasted to a stop, and found that all electrical accessories were dead. Power windows, sunroof, radio, heater, all lights, turn signals, even the emergency flashers were dead. Oddly, the engine would crank normally, but would not start. I had to have the car towed home.
I found the Volvo wiring diagrams and went through the engine bay fusebox, the driver’s side fuse box and the fusebox in the cargo area looking for any hint of trouble. I disconnected the battery ground, so that I could access the ‘lower level’ of the engine fusebox. All fuses looked good. I reconnected the battery, and noticed the interior lights came on – they were dead earlier. The car started, and ran fine. Everything worked again. The airbag light was on, I guess because I forgot to put the ignition key switch in position 2 before reconnecting the battery.

2nd Failure
I drove the car, but after about 1 mile, I noticed some idiot lights come on and a BRAKE FAILURE message. The gauges went dead again. After a minute, the engine stalled while idling after I stopped the car, and would not restart. I disconnected and reconnected the battery, and was able to start and drive the car. Again it seemed OK, and I drove it home. Again, I went through the fuseboxes, this time carefully removing all the large terminals, cleaning and retorquing their screws and nuts. I pulled every fuse (including the 4 or 5 big 50A fuses back by the battery) and relay I could find and re-seated them back in their original places. I was able to drive the car afterwards, and it seemed fine for about 5 trips totaling 100 miles.

3rd Failure
The third failure incident happened on 11/29/17. About 3 miles into a drive, the speedometer went to zero, the ‘BRAKE FAILURE’ message came up, and the ABS and traction control lights came on. The engine was running fine, and all other electrical accessories seemed fine. I was able to drive back home.
After I got home, I restarted the car. The instrument cluster still showed the same issues, but the engine was missing, or at least running very poorly.

Current status:
Yesterday, the car restarted, and seemed to run fine. i.e. it didn't seem to be in 'limp-home' mode now. These sorts of issues seem to come up a lot when I googled "BRAKE FAILURE' on the P2 chassis, and the only resolutions I saw were related to CEM replacement. XeMODeX offers 'rebuilding' and cloning, so I thought I'd pop the CEM out and inspect it. (I design electronics for a living and have access to a pretty decent SMT rework area and top-notch techs.) I was hoping there'd be some hints of bad solder connections or thermal stress. There wasn't. The CEM 'looked' great. Unfortunately, the entire PCB is conformal-coated, making my idea of re-flowing any suspect solder joints likely to do more harm than good. At this point, I have some hope the issue was a flaky relay on the CEM. I pulled all 12 of them and, being identical, purposely re-installed them in different sockets.

So, I'll continue to drive it on non-critical trips, and hope for some further clues.

What a pain - and I thought the P1 Lawnmower Syndrome was bad...

[June]

...It ended up being a corroded main power cable where it meets a connector in the left lower corner near the REM...

Right - I was hoping to see some evidence of something like that in the REM or engine bay fuse panel. But, I've gone through both and despite being 16 years old, everything looks great. What happened to yours? Spend some time under water? Battery outgassing?

I had the sudden loss of power problem and the lower portion of the under hood fuse panel plus cable had to be replaced. I never have had the problem again. June

[oldandbroke]

Hey any chance you've had any breakthroughs in the past few days? I have some very similar symptoms this morning.

Right now my priority is just to get the car home, but then I think I will use your thread as a guide.

Thanks!

[precopster]

The reason for the corroded connector was that the car sat without a rear tail light in a panel shop and we all know that they often leave cars in the rain without adequate cover while waiting for parts.

[Brickbat]

Hey any chance you've had any breakthroughs in the past few days? I have some very similar symptoms this morning.

Right now my priority is just to get the car home, but then I think I will use your thread as a guide.

Thanks!

Your symptoms sound different. My issue always manifests as all the brake warning/ABS lights coming on, 'BRAKE FAILURE' showing in the message center, and speedo/tach going to zero.

As I mentioned in my summary above, I pulled and moved all the relays on the CEM around, thinking that IF it was a bad relay, I'd like to have it in a different location to see if I get different symptoms. After the CEM relay-swap, the car was fine for several trips, but then the same issue popped up again.

All I've done since is do the same relay-swap, but this time on the REM. I've not had a chance to drive it much since, so don't know if that did anything or not. If the problem persists, I'm contemplating buying a junkyard CEM, and having it 'cloned' from the original. Looks like that'll run around $250 altogether, so it'll be an expensive experiment...

[abscate]

Did you replace or at least disassemble and inspect the ignition switch? You are way past the MTBF on this.

[precopster]

Did you replace or at least disassemble and inspect the ignition switch? You are way past the MTBF on this.

Not on P2s. The ignition switch was redesigned about mid 2000 for the P80s and was not particularly problematic on P2s though it wouldn't hurt to check it out and perhaps swap in a good used one. While you're there a good used alternator may help out. I'm not sold on cheap alternators.

[abscate]

You are right as always, Mike.

I think the change was even a bit earlier, late 99? I have a 10/98 build with the P80 switch while my parts strip 99 had the later switch.

[Brickbat]

So, here's the update.

The issue has popped up 4 times. Each time, removing the battery cable basically 'reset' things back to normal. The issue hasn't occurred in the last 2 weeks over 400 miles of driving. The last thing I did was mentioned above - I removed and swapped the location of all the relays in the REM. There was also a king-sized relay that was a one-of-a-kind, precluding the switcharoo, so I popped its plastic housing off, and cleaned the contacts (though they looked pristine).

Is it really fixed? Hard to say, other than so far, so good...

[oragex]

This doesn't look like a CEM to me, at least not a typical one. Usually it won't affect the radio.

Undoing a battery post looks like it's resetting everything so a module may act up, such as an immobilizer and one potential cause would be power delivery to this module. Even just a bit of corrosion on a cracked cable at the alternator can trigger this. Plus, a new cheap alternator is not the best idea. It may be fine but the regulator may act up. I'd try swapping the regulator with a used (and correct one for the vehicle).