Help with Vida Diag codes - Brake Failure Warning - Comm issues

[mikeamondo]

Car - 2004 XC70
Diagnostic Equipment - Vida / Dice although I'm very inexperienced with it.

I've been trying to track down an intermittent communication / module failure issue for a month or so now. I can go 200+ miles between issues. Here is a link to the thread I was working thru ... viewtopic.php?t=81959 if you'd like the full, in depth history.

Right now, I've done the following:
Pulled the ECM and TCM and cleaned the pins with contact cleaner & toothbrush, replaced with a nice coating of dielectric grease.
Pulled the CEM, removed the connector and did the same cleaning / greasing on the pins, and reinstalled.
Took out the air cleaner box, and removed a few of the connectors located on that plastic riser - I could only get 3 of them to come apart.... gave up on the rest. Those I got apart, I cleaned as above and added grease.

RESULTS - so far, I can say it feels BETTER.... but I still had the issue last evening. No consistent timing / conditions on it occurring. I think it's better because the issue seems more infrequent and having fewer faults than when I started.

The Event - Driving home, 12 miles into the drive, ac goes warm, tach, speedo and temp guage die, Brake Failure Warning - stop safely' warning on dash, ABS & brake light on. No actual braking issues, of course, and no transmission warnings or limp mode. Continued home, and the fault remained as described, car running great. Turned engine off and restarted and the problem was gone. Historically, I can say I may drive another 200 miles or more before it happens again.

Pulled the codes with Vida.... after that single restart.... Here's what I got from around the time of the event:
BCM E000 Control Module Comm - Faulty Communication. 1 cycle ago
372 CEM E000 Control Module Comm - Faulty Communication 2 cycles ago
372 CEM 1A5F - Communication with BCM 2 cycles ago
CEM 1A61 - Comm with TCM Missing 2 cycles ago
CEM 1A62 - Comm with ECM Missing 2 cycles ago
284 ECM 9400 - Brake pedal Sensor Signal Missing -- 1 cycle ago

I'm starting to think CEM or one of the relays on it.... What do you guys think? I really want to avoid blindly spending hundreds of dollars taking a stab in the dark here.....
Thanks!

[Fataqui]

Hi

After reading everything you posted I would definitely be looking at getting the CEM repaired or replaced. Up where I live you can get a good used one from a junk yard for $50 or $60. I would personally do that and then send your unit and the good used unit up to xemodex and have them transfer your units info to the good used unit. That would run around $300 to $350 depending on how much the junk yard would charge you for their unit, or you could just get a complete replacement unit from xemodex which will have all the upgraded relays in it, and those cheap relays Delphi used are mostly the main reason Volvo CEM(s) fail. Now, for me doing one or the other would entirely depend on how long I would be keeping the car that has the problem. As a side note... I have seen many customers of mine do both those things with great success so either way will work, but for longevity sake the complete replacement is what I would do if it was my baby, LOL! And yeah, I am laughing, but when a car has taken you around the world many times over, 700,000+ miles and / or holds many irreplaceable memories you take care of it, no questions asked!

[precopster]

As a born pessimist I understand where you're coming from so let me share what may work.

These 2004 CEMs are not Delphi units like the later ones and therefore swapping relays won't work. Your symptoms seem pretty consistent with CEM failure.


If you get hold of a used unit contact Yagger or Doublebug. They will send you some photos of which pins to short. on the main IC (pins 8 & 9 from memory) so they can extract the programming and rewrite the new (used) CEM over the internet. You'll need a pair of tin snips to tear each corner of the aluminium heatsink cover over the main IC. Henry (doublebug) and I have successfully rewritten about 6 CEMs on various cars. Total cost is one hour of their time which is a lot less than XeModex' fee when you aren't 100% certain of the diagnosis.

[mikeamondo]

Thanks for the input... @Fataqui --- Is there any way to be sure you're getting a good used CEM? I mean, if you started my car, even drove it for a couple days, you'd say the CEM must be just fine. Heck you could drive it for a week. And ... how much is that spiffy all new upgraded one from those guys?

@precopster --- lots of stuff in there that was gibberish to me, but I think I got the basic idea. So, would you be shorting pins and tearing heatsink covers on the used one I picked up from a junkyard... I assume? So the same basic idea, just those guys can program it remotely? May be a bit beyond my technical ability.

Does CEM failure often present symptoms this intermittently?

[SwedeSammy]

I have a 2007 V70 and I wanted to share my experience and what ended up fixing the problem.

My car was parked for 5 months while I was away on a business trip.

When I came back, the battery was obviously weak. I jumped it to start the car, drove it home, took out the battery and charged it at home.

The battery appeared to charge fine and when reinstalled in the car, cranked the starter motor and started the car fine. Sometimes the crank took a second longer, but the car always started.

One weekend, I drove the car to buy groceries. when I started the car up to drive back home, after a few seconds of low speed driving, I heard a sound that appeared to come from the back brakes and I noticed that the transmission was in limp mode and the ABS warning light flashing. Another time after starting the car, the check engine light was also flashing and the transmission went into limp mode again. The issues happened not every time but maybe every other time that I started the car.

The car had the following codes stored,
CEM-1A5E
CEM-1A5F
CEM-1A61
CEM-1A62
CEM-3F83
SAS-0016
SAS-0018

I searched forums for possible causes and one person said that when he installed spark plugs and these issue presented themselves. I had recently changed my spark plugs to NGK, so I changed them back to the old Volvo brand spark plugs that I had recentlytaken out (they were still in decent shape). Changing the spark plugs back didn't solve the issue for me.

I also found people that started water intrusion under the hood at the CEM caused this issue as well. I didn't get a chance to look at the connectors yet. This might still be an issue for some people.

Online, other people said these cars don't like weak batteries, but I thought my battery was still fine since it cranks and starts the car fine. However, keeping it parked for 5 months couldn't have been good for the car, so the battery was always a possibility in the back of my mind.

I even bought an electronic battery tester and it said that my 3 year old 70AH 600A EN Volvo battery had 97% State of Health and that the cranking amps were very close to the reading on the battery 600A EN rating.

I took a chance and bought a new 95AH 800A EN Bosch battery and installed it in the car. I've been driving the car for a few weeks and the communications, transmission limp mode, ABS brake light, and other communications issues haven't returned yet.

I believe that the battery voltage during cranking was dropping too low and taking out the CAN Bus between the different modules.The CAN bus is like 5 volts, so I don't know how the starter can crank and start the car at 12 Volt rating and the 5 volt CAN Bus can drop out.

The lesson learned is that if your battery cranks and starts your car, the battery might still not be good enough for the electronics. If you have communications issues with your car, try replacing the battery and that might solve your problem.

I felt that I had to share my experience because other threads with these issues that I experienced didn't appear to have posted the solution of changing out the battery. Also the cause of my problem might have been different than similar threads.

[motormikeyman]

Same year, same problems. However, my CEM looked like it had already been upgraded with the heat sink and showed no water or had any heat related issues. Cleaning the main CEM connector helped but the problem would reappear at random, then go away if I cleaned the connector again or sometimes just wiggled it. There was no way I was changing all of those pins so I took a chance on a contact enhancer that some of the guys at a crane repair shop recommended. Been 3 months and no issues since applying this to the pins and sockets on the main CEM connector.

https://www.partsdrop.com/index.php/007 ... gK6dPD_BwE