It started with a rough sounding engine. Then a CHECK ENGINE light, ENGINE NEEDS SERVICING, TRANSMISSION NOT COMMUNICATING messages and codes P0600 and P0700. Since the car has 273,000+ miles on it I decided I'd change the O2 sensors, clean the MAF sensor, clean both the ECM and TCM and flush the tranny fluid. Ran great for a few weeks then more craziness: BRAKE FAILURE message and ABS light while intermittently the tach, speedo and temp gauges all stop working. And finally the cherry on top: IMMOBILIZER SEE MANUAL. I used the ol' turn the key to the accessory position five times and crank it and it worked. Now all of the above warnings and lights come on with a loud thumping under the dash. Once I do the key trick and the car starts all the lights and warnings disappear and the car runs like a champ. When I do a scan I get no codes. Anybody experience similar issues?

 

Are you scanning the car - all the control units? Or just an OBD scanner?

You may have a CEM problem, but a complete scan needs to happen first (unless you find obvious water damage to the CEM)

Common failures courtesy of xemodex

 

I did indeed send the CEM to Xemodex who found it in good condition. Xemodex then suggested I send them the DEM. In all the forums and message boards I scoured looking for answers to the myriad codes, messages and wacky symptoms the car was exhibiting no one had mentioned the Haldex DEM. So I was reluctant to go that route but since I had few options other than sending the car to the wrecking yard, I sent in the DEM. Sure enough, it had water damage. Xemodex wanted $900 to fix it. The car has 273K miles on it and probably not worth $900. I had them send it back to me. In the meantime my Volvo guy said he had a couple of parts cars and he would see if he could swap out the damaged DEM for one that works. And, dang, if he didn't get it fixed. So that was the ghost in the machine. The Haldex DEM was bad. Hope this helps someone else.