Car runs fine, however, intermittently the electrical system/battery will do a complete “disconnect” after turning the car off. If you disconnect the ground terminal for the battery (the alarm will chirp when you do this) and then re-connect it – it will all then work normally and run fine. However, there are several warning messages – to check/re-set the air bag sensors. The Volvo dealer cannot find a problem or re-create the same issue. Otherwise car works/runs great… until the next “disconnect” which could be weeks/months apart. There seems to be no rhyme or reason to it. However, again – if you “re-boot” the system by disconnecting the battery and then reconnecting it, it will work fine…???
Any suggestions?
Thanks!

 

Check for loose connection as master power connection.

 

Thank you - where is the "master power connection" ?

Thamks again

 

My son's S80 does something similar. About once a month, his car will, for no reason .......die. This happens while he's out & about. Run some errands, come out and it's like car battery has drained, whilst running fine 5 minutes prior. Jump pack starts car in a few seconds. Voltage @ batt term in engine compartment read 14.1V. Checked continuity of power cable from trunk to engine. 0.03 ohms, same as leads of meter touching each other. Weird huh?

 

My 04 S80 has the exact same problem. It usually happens after driving at high speeds. I am wondering if it has anything to do with the aftermarket keys I have.

 

I hace exactly the same problem...see my post S80 Electrical problem - intermitant.
Surely someone has the answer. I'm replacing the alternator because it's a little low on output but more I think about it, the more I think ECM or Body Control Module
Help!!!
regards
Rod

 

Do the head lamps still work after this happens or is it a complete failure? If the lights will still operate it could be something as simple (or complex) as a dry joint in the fuse box pcb or be like the Range Rover, and have a dry joint in the immobilizer.

 

I am having the same problem as well with my 99 S80. I drive it around for about 20 minutes and after I park it, shut off, I try to start it and it starts and then just dies. I try it again, it starts then dies like it is getting no gas. Then I go in the house and 10 minutes later the car is completely dead. I wait the next day, unhook the battery cable and boom, car alarm goes off and I can unlock my doors. I then go and start the car and it starts fine. This just started to happen. Did anyone solve this issue yet?

Update...I took it in to a Mechanic and they pulled the DTC Codes
ECM-720A
ECM-E003

I was referred to the dealer.....any help before I go there would be great.

 

All these issues are referring to the CAN bus faults.
CEM & ECM cannot communicate to each other so car starts than dies.
That looks like CEM issue. Because when you later turn the key and starter does not crank it means CEM does not allow it. After you disconnect the battery CEM and all electronic modules are restarted. But also the cause can be wire harness issue of the CAN bus wires (twisted pair of green & white wires). When CEM detects a lot noise (sending/receiving errors) in the CAN bus it completely disconnects form it (that is when car completely dies). Communication is restored only with cold restart (disconnecting the battery). So the issue can be any module on the high speed CAN bus (ECM, TCM, ETM, ABS and CEM). Usually most faulty modules are ABS, CEM, ETM. Most hard issue to resolve is in the harness under the hood because it is possible to find it only when the issue is reproduced constantly for some time.

 

Thanks for the reply, I am hoping the dealer can pull more codes and zero in on the module that is failing. Pain in the ****......