2004 V70 Electrical hell; CEM, iImmobilizer? ( bad replacement CEM, Xemodex excellent) Topic is solved

[RocketUSA]

Hello all. Sorry about the long post, but let me introduce myself. I fancy myself a decent "car guy" and along with a buddy we work on and maintain our families cars. We've tackled lots of complicated issues over the years, and we help each other out all the time. Currently we're wrestling with a problem I'm hoping to find a solution to. I helped him find and buy a 2004 V70 last fall, and it was a great car until the heat of summer hit. All sorts of problems started cropping up regarding what we "think" are CEM related issues. In short, limp mode, SRS errors, DIM non-responsive. Pretty much the common stuff people get. Resetting the fuse (34?) would bring the car back to normal until the next "limp mode" episode.

After tons of reading and research, I determined that a call to Xemodex was in order. They suggested we heat the CEM with a hair dryer to see if we could replicate the symptoms. Sure enough, after about five minutes the car started freaking out again. Problem identified, or so we thought. Pulled the CEM, sent it off to Xemodex, which they promptly identified as having a fault. They did a program transfer and sent back a new one. We installed it back in the car, and viola, everything worked great (we still had the SRS error, but knew that was another fish to fry).

We run the car for 10 minutes or so, feeling pretty proud of ourselves over the accomplishment, as we put tools and work lights away. Then it came time to shut the car off and lock it up for the night. This is where things get interesting.

Once the car was off, we locked it with the FOB. The locks all engage, but then we notice the dashboard LED is fast blinking. Hmmm, why is it doing that? Did it always do that? No, that's definitely weird. I ask him to unlock the car. FOB doesn't work now. We manually unlock the door and there are no interior lights. Uh oh. We try to start the car. Starts, but dies in about five seconds with nothing displaying on the DIM. Climate controls all work, though. Try to restart. Cranks but doesn't start. Try again. Starts for a few seconds and dies. We try pulling the fuse as we have in the past to recover. Now the alarm goes off when we put the fuse back in.

To recap, we mailed off a faulty CEM that was causing intermittent trouble, and replaced it with a new and upgraded CEM. Now the car is completely dead in the water. Called Xemodex and they suggested disconnecting the positive and negative leads from the battery and shorting them out on each other for 30 minutes. Tried that, didn't work. They are also at a loss as to why this fix has completely regressed the car, although state that they've seen all sorts of freaky electrical things over the years, so this goes down as "one of those." They're looking into sending a new unit, but with all the quality control checks they doubt it's a faulty unit. Now we can't even connect the battery without the alarm going off.

Here are my best guesses why this is happening:

• 1. Although the CEM was faulty, it was caused by another source. Not sure I really believe this because it was very typical CEM failure as mentioned by lots of people.

• 2. Maybe the FOB needed to be reprogrammed, and now the FOB and the car don't "know" each other anymore and need to be reset.

• 3. Maybe the immobilizer is trashed

• 4. Maybe the CEM from Xemodex was faulty out the door.

I'm at a loss right now.

[oragex]

Pulled the CEM, sent it off to Xemodex, which they promptly identified as having a fault. They did a program transfer and sent back a new one.

Not usual to have them send a new reprogrammed unit. Usually they reflow the original unit and send it back. Do they still have the original unit? Maybe their program that was loaded in the new one that was sent, didn't account for information such as the car security system, and now the computer is cutting the ignition to prevent starting the car.

As for the original issue, besides the CEM the 2004 models also have some issues with the ECM electrical contact https://www.matthewsvolvosite.com/forums ... 57#p368657

[RocketUSA]

Thanks for the feedback oragex. We talked to Xemodex and they said that was the only option for the 2004 V70, no repair and return. To their credit, the techs have been very responsive in working the issue over the phone. At this point they want to see the CEM back and run some tests on it.

I'll take a look at that link. I'm hoping it's something simple at this point.

[doublebug]

I would blame new CEM (or it's socket) because the car has the issue with both networks Hi and Lo speed.
and CEM is the only module that is connected to both of them.
While car is without CEM you can check CAN bus resistance between green and white wires in the twisted pair. Check both networks. Resistance should be about 60 om.

[RocketUSA]

I apologize for the late reply on this, as I thought I had already done so. Turns out the first CEM from Xemodex was faulty. I don't know what the reason was, but upon receiving the (2nd) replacement the car has been running like a champ ever since. To their credit, Xemodex was awesome through the entire process and I would highly recommend them.

[oragex]

Useful update

[abscate]

Green checked and subject remarked with solution

Thanks for follow up , that's huge for the Forum collective!