CEM problem, help needed

[R-P]

I have done some hands-on research in the matter since I had similar issues. The heatsink and even a 24/7 running fan only helped if outside temps were below 30ºC.

In my case, I have yet to manually overheat the CEM to see if my issue is really gone, but so far it has not failed me even though we have seen temperatures where it would normally fail. BTW, I measured the temperature of the processor and the programmable memory next to it, and the heat they produce was negligible. While I was not driving around, so the CEM might have been idling, I could simply not measure any increase in temperature, so the whole heatsink solution is imho only a band-aid.

The only thing I did was locate bad solder joints (only found one) and fix them (it).

Watch the last 10 seconds, the rest is just plain boring Do listen with the sound ON to hear the CEM loose its marbles when applying heat to a specific pin on the memory-chip.

I cannot speak for other CEM's but my diagnosis for my specific one is that lead-free soldering has caused yet another machine to fail.
(Even though I think carmanufacturers are exempt from some of the lead-free restrictions, this is quite typical for lead-free soldering, which has caused imho a giant spike in defective equipment.)

[R-P]

Just to update: it did fail again and I brought the CEM to a repairspecialist. He replaces the entire eeprom memory chip. Finally some answers as to what they actually do... had I known this, I would gladly have paid the 200quid (225€) years ago. Even if I had found an electronics specialist* who could copy the eeprom for me, my solderingskills are good but not good enough for such an operation.
It even came with a new lid for the CEM with a build-in 30mm fan (again, fan doesn't really 'cool' but preventing stagnant air rising too much in temp is never a bad thing).

I think the operation was succesful but haven't had prolonged >30ºC temps to be absolutely sure.

* I also discussed this problem on an electronics forum and had found someone with the necessary equipment and general knwoledge who was willing to fiddle around with the CEM and attempt to copy it to an entirely different CEM, but he lacked the time and I wasn't sure if it was wise to mess around with the CEM in that way.

[Green440wedge]

I had some of those issues last year and fixed it by changing the ignition barrel switch.....

[flowstyle]

Originally Posted by R-P

Just to update: it did fail again and I brought the CEM to a repairspecialist. He replaces the entire eeprom memory chip. Finally some answers as to what they actually do... had I known this, I would gladly have paid the 200quid (225€) years ago. Even if I had found an electronics specialist* who could copy the eeprom for me, my solderingskills are good but not good enough for such an operation.
It even came with a new lid for the CEM with a build-in 30mm fan (again, fan doesn't really 'cool' but preventing stagnant air rising too much in temp is never a bad thing).

I think the operation was succesful but haven't had prolonged >30ºC temps to be absolutely sure.

* I also discussed this problem on an electronics forum and had found someone with the necessary equipment and general knwoledge who was willing to fiddle around with the CEM and attempt to copy it to an entirely different CEM, but he lacked the time and I wasn't sure if it was wise to mess around with the CEM in that way.

That fix looks really neat! Do you mind to share the details of your repair specialist? I'm experiencing the exact same overheating problem.

[Xc70 xo]

Hi, sorry to hear about your problems. My vehicle had the exact same problems as yours
I have an xc 70 on an 03 plate ,had intermittent problems with things stopping working and various warning messages,I would stop the car and restart ,most of the problems would go away!
On one trip it got really bad and took hours to get home,
Always happend on a hot day when the car was hot as well,so after reading up as muchas I could on the problems.,I rang Volvo diagnostic ,they were 99% sure it was the CEM ,so I sent it of ,had it repaired,then refitted it , NO More Problems,just lovely trouble free motoring!!!!!
Good luck!!

[Parknest]

I think I'm having the same problem with my XC90.

After driving for a certain length of time (more than 2 hours, I think). I would hear a thump from the transmission, what sounds like some relays clicking, a loss of power to the radio/CD, indicators, wipers and the instrument panel. The climate control would still be working, the headlights would still be working and it would drive fine. Before losing the instrument panel, I would get "Brake failure Stop safely" and SRS messages on the display. This has been going on sporadically during the time I've had my XC90. It happened today after a run out to Burnley and Oldham. I was able to get home and I scanned it with my scantool and these are the fault codes that came up.

Diesel Engine
ECM-A03B Communications, Central Electronic Module. Faulty Signal
ECM-A500 Control Area Network (CAN) Fault. Faulty Signal
ECM-9210 Cruise Control. Faulty Signal

SRS
SRS-00D5 SRS Indicator Lamp. Signal Missing

REM
REM-9F21 Cargo Compartment Lighting. Faulty Signal.

CCM
CCM-0021 AirQuality Sensor. Internal Fault.

ABS
ABS-0094 Communication Between Control modules. Communication Problems With Active On Demand Coupling.

CEM
CEM-1A64 Communication With AOC Control Module Signal Missing.
CEM-1D07 Control Module Internal Fault.

CCM-0021, ABS-0094 & CEM-1A64 were already there and the last 2 relate to a faulty DEM so they can be eliminated for now.

2 of those fault codes ECM-A03B & CEM-1D07 seem to point to a faulty CEM.

Can anyone shed any light on this?

[MWMan]

This looks very much like the CEM overheating problem discussed in this thread. The same issue occured with my wife driving the car (early morning in winter using just about every electrical device on the car and the heating turned up). She had to be brought back by the AA.
I scanned the car with VIDA and came up with similar fault codes to yourself.
I honed in on the CEM being the culprit after finding a few threads on the internet about the same thing. All of them were the XC90's !!!