2005 XC70 D5 AWD – CAN communication loss ECM ↔ CEM – no start after module replacement

[Hancu]

Hi everyone,

I’m writing this post because I’m honestly running out of ideas and hoping maybe someone here has seen something similar before.

The car is a 2005 Volvo XC70 D5 AWD (P2).
This is actually my first car ever, and I’ve really fallen in love with it, which is why I’m still trying to save it instead of sending it to the scrapyard.

At this point the car has spent more time in workshops than with me on the road and I’m trying to decide if there is still hope.

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Full story / symptoms

A few months ago, the car stalled while driving for the first time.
After some time, it restarted and continued driving normally.

Around the same period, the heater core also failed and was later replaced.

Some time after the heater core replacement, the car stalled again while driving.
This time it did NOT restart anymore and had to be towed.

Since then, the car has not started at all and has only been transported by tow truck between workshops.

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Current diagnosis

The latest workshop diagnosed:

CAN bus communication loss between ECM and CEM

According to them:

* the main wiring harness was checked,
* no obvious wiring fault was found.

They suspected a faulty module and replaced/cloned the suspected unit (copied the data/configuration from the original module to the replacement).
Unfortunately after replacement and cloning/programming, the problem is STILL exactly the same.

The car still does not start.

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Additional info

* Car has spent almost 4 months in workshops total.
* First workshop was in Kirkjubæjarklaustur, Iceland.
* Then the car spent about 2 months in another workshop in Vík, Iceland.
* Multiple mechanics have looked at it.
* The current workshop basically gave up and suggested finding a Volvo electrical specialist.

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My questions

At this point:

* what would YOU check next?
* Has anyone seen a similar ECM ↔ CEM communication issue on a P2?
* Could this realistically still be:
* CEM?
* power/ground issue?
* CAN short from another module?
* immobilizer related?
* ignition relay?
* water damage somewhere?

I’m especially interested in:

* common hidden failure points,
* splice points,
* known P2 weak spots,
* things that can kill CAN communication even after module replacement.

The car is honestly too good to throw away:

* D5 AWD,
* comfortable,
* quiet,
* perfect Iceland road trip car,
* and I’d really hate to part it out if there’s still a realistic chance to save it.

Any advice would be hugely appreciated.

[ignatz]

Issues with my 06 S60 T5 started with an intermittent "no start". Only one time during this 3-4 week period of intermittent starting, I saw an Immobilizer warning message. I took it to my local Volvo independent shop and they replaced the antennae ring. Now the car will not start at all.
They had my ECM cloned over to another used ECM and still no start. My newer ECM and CEM went to Xemodex and they said everything looked good.
Now I had my non-running S60 towed to the Volvo dealer who accepted the challenge, but still couldn't get it to start.
The dealer called Volvo headquarters for help and the big Volvo computer in the sky said my key wasn't communicating with the ECM and CEM.
Volvo, re-keyed my car, re-flashed my ECM and its been running ever since. With the CEM being original in age and removed many times, the brake lights stayed on after the car was turned off. A broken connection or two also added a new CEM to my bill.
This whole ordeal took about 4 months. All this for an intermittent "no start".

[vtl]

You need to read the codes with Volvo's special software called VIDA. It requires special adapter called DiCE. VIDA also accepts other J2534-compatible adapters, just make sure it has dual CAN-bus support.

2005 is not known for frequent CEM or ECM failures. CEM's seal may leak and let water in, which can destroy it. But you said they cloned it.

As ignatz mentioned, an ID48 chip in key can die. Rarely, but it happens. It would not stall the already running engine, though.

[Hancu]

Thank you guys. I will talk with my mechanic and one more workshop. I hope it will work