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Q: Engine & all electronic power died on highway on 2004 Volvo XC70

This has happened 3 times. Volvo and independent garage cant find anything wrong with car.

I was driving on highway at 100km. Car suddenly 'bucked', a 'thunk'sound came from it, then all power, electronics and engline died. Car was dead. I rolled into hard shoulder. No electrical power in car at all. After a few seconds i tried to start car, No power. Left car 5 mins, then car started, we went back on road, drove 300yards, card id the same thing, big thunk, all electro died and I pulled over.

The Air bag code came on. and Orange Engine light came on.
Volvo cleared all the codes, said car ran fine. They suggested I have the remote starter removed as they said it could be grounding or causing car to stop the engine. I had the remote removed but am scared to drive car as I fear thecar will stall/die again, and i will be hit by someone.

I did some research on web, and wonderer if its a defective alternator, or
the immobilizor, or engine switch perhaps?

Volvo told me I may have to replace the CEM. (central Electronic module) if the engline dies again, but that is very expensive. Any thoughts on what the problem is??
as I am scared to drive the car.
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This vehicle is a complex network of computers all working together, and adding any electrical device is asking for trouble, so removing the remote starter is a good decision. It's unlikely the alternator or immobilizer are the problem, and possibly the ignition switch, but I doubt it.
What I would do(if it's not too late) is pull the diagnostic codes from every module on this car and see if there is some data there that will help point you in a direction. The CEM (Central Electrical Module) is the main computer that all information goes through, and a problem with the CEM could do this, but I would need much more info to make that decision.
Did a Volvo Dealer tell you the CEM was needed? Can you provide any info about why they recommended this? Do you have the codes that were stored?
You are going to have to pay good money, to get the best qualified technician to address this, otherwise in an effort to save money, your in for wasted time and money and possibly adding new problems. Take this to a very good Independent or Dealer.
This has happened to my Volvo XC70 3 times now, last time just 3 days ago. I have taken it to the dealer twice and to an independent mechanic. Same answer, diagnostic shows nothing wrong with car. ONce they unhook it from diagnostic, it runs fine as if nothing ever happened. Dealership mechancic says replace CEM but no guarantee that will fix it, admits that is what he thinks might fix it. Another friend, who has a friend, (HA HA) who used to work at Volvo mentioned a problem with the battery but have not had that checked yet.
When I asked the dealer what the codes were all he said kicked out was miscommunication no numbers. He also said that no mechanic can give you a guarantee, that it is volvo's policy to start with CEM module and if that doesn't fix problem then they will look for other problems but not until you replace CEM first.
I have a 2005 S60R which has exhibited very similar characteristics. This car has been in CA for a long time on VERY rough roads. So rough that they broke the front stabilizer. Yes, they are that rough. The only thing I could find which solved the problem was to have the local repair shop seat and unseat all the connectors. Clear code, and no problems for LONG time afterwards. The only thing I figure is that there are intermediate comms between the CPUs and the whole system goes wiggy. I actually had the 4C try to "correct" for me while driving at 70 MPH, nearly made me crash because what it thought the car was doing and what was happening in real life was NOT the same. CPUs in cars are not always good. I'm still POd that Volvo takes ZERO responsibility for what is foreseeable -- cars get rough service, and wires do not always connect. This is a commonly known problem. Volvo corporate didn't care at all and wanted to charge me $3K to change out the various computer modules. I told them how high to jump, and in what direction. As an Engineer, these kinds of problems really tick me off!
very very helpful I to was apalled at lack of responsibility volvo wants to take I was told they would replace most expensive module and if that wasnt it they would try a different one and so on and that no mechanic can guarantee repairs
That is why I stick with cars other then Saabs or volvo's....saturns..... jags...they all are horrendous when they act up!!!
good luck could be any of the above parts and you cant test them cause when the car is good the parts test good!!!
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