V70 gremlins

[Theshagginwagon]

SOLVED!!!!
after taking the cem out and cleaning all the connections I placed a 25mm heat sink on the cpu and removed that metal plate covering the cpu. Once this was done the ecu connections were double checked and everything put back together. The car now starts every time regardless of how hot it is outside. I drove from amarillo to Galveston while towing a trailer without a problem. Thank you everybody for all your help

[abscate]

The only time I saw anti-skid warnings on my 2004 v70, it preceded a wide range of faults and warning lights, and was solved by removing the metal RFI shield from the CEM circuit board, and (perhaps overkill) adding heat sinks to both of the chips that are said to overheat in the CEM. As the heat sinks are cheap, I also did the same with the REM, despite having no faults associated with it.

This process not without risk for the inexperienced - one wants to photograph the locations of the CEM relays and mark each relay, paying careful attention to the proper plug-in location for each. Getting the CEM in and out of its clips is also a puzzle for many, but it will make more sense if you look at the mounting bracket once the CEM has been removed.

As this is a "zero parts cost" fix, and is easily reversible without any damage, it may be worth trying if you have a spare half hour.

Absolutely smoking diagnosis.

[jonesg]

SOLVED!!!!
after taking the cem out and cleaning all the connections I placed a 25mm heat sink on the cpu and removed that metal plate covering the cpu. Once this was done the ecu connections were double checked and everything put back together. The car now starts every time regardless of how hot it is outside. I drove from amarillo to Galveston while towing a trailer without a problem. Thank you everybody for all your help

Some people installed computer cooling fans on the cem, apparently it resides in a dead air pocket under the dash with little air flow.

[Theshagginwagon]

On a side note, after all of this was done the car works flawlessly....mostly, the issue I am having now is now the shifter light on the console will not light up, I cannot go into manual mode and I have a warning saying gear selector reduced function. I believe it is the ribbon connection that is shot but upon further inspection could not find a smoking gun. Could the recent work on the cem be related and if so what is most likely the problem

[mrbrian200]

Once it's begun to act up the CPUs (internal) transistor gates have physically degraded. This doesn't necessarily render the CPU inoperable, but it pulls more current and generates more heat to do what it does.

If the additional heat isn't dissipated through extraordinary measures the CPU will begin to overheat and shut down to prevent thermal-current runaway where it would self destruct in a ball of smoke (literally). Each overheat-shutdown event potentially degrades the CPU further where it pulls even more and more current.

As excessive heat is the main culprit for this physical degradation, adding a fan to push air through the dead air space behind the dash is a preventative measure for CEMs that have not yet exhibited signs of overheating, and thus have CPUs that have not substantially degraded in this fashion.c

If symptoms have occurred, to prevent further damage, a heat sink will be necessary.

For those who have experienced CPU overheat symptoms: we cannot access these chips' internal temperature sensor data to determine if our cooling solution is keeping temps low enough to prevent further degradation (probably 50C or lower). In this case I say the bigger the heat sink the better and a probably a fan too.

Edit: a fan to push air into the dead space not only keeps the CEM cooler and happier: DIMs also are noted for failures, as well as AUM/Radio failures. With the fan, CDs don't come out of the radio broiling hot anymore. Both of these other known failures are likely heat affected in many cases.