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Several months ago I picked up an S60R for use as a winter vehicle. It’s been a great daily driver since, but when I was on the highway today I experienced an immediate and complete loss of all electrical systems, including engine, turn signals, and brake lights. The gauges on the dash are frozen at 60mph and 1800rpm. The battery is still connected, there was no drama before or during the shut down, and the car is completely stock minus a lift kit and rally wheels.

I work on cars a fair bit, but this seemed a bit odd. I have my suspicions, but wanted to see what the community has to say.
 

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I would start by checking the battery, then alternator and then voltage regulator. Are you getting any function of anything like the radio or lights when the key is in ACC or I position?

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I have zero function of any electrical systems, and everything cut out instantly while the vehicle was running. There was no low battery warning light or check engine light on the dash prior to cutout. I plan to check battery voltage later today.
 

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You don't mention being struck by lightning, so a massive over voltage leading to fried electronics can't be the cause of your electrical system failure. My guess is that the Central Electronics Module, or CEM, is inoperative, due to loss of power. If it was working, you would be seeing digital trouble codes on your dashboard display. Also, if it was working, the speedometer would not be frozen at "60 mph." You might have a bad connection in the (+) positive side of the power supply, or a bad ground connection somewhere. Also, you should check the serpentine belt and make sure it is in good condition. However, a failure of this belt should not cause instant failure of the CEM to function, so I doubt that you will find a damaged serpentine belt.
 

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While there is no reason to think you have a blown fuse, it is also true that fuse connections slowly oxidize over time, and eventually, the thickness of the metal oxide will become an effective electrical insulator, and result in an open circuit. For this reason, it is a good idea to replace the fuses every 10 or 20 years, even if they look like they are in good condition.
 

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While there is no reason to think you have a blown fuse, it is also true that fuse connections slowly oxidize over time, and eventually, the thickness of the metal oxide will become an effective electrical insulator, and result in an open circuit. For this reason, it is a good idea to replace the fuses every 10 or 20 years, even if they look like they are in good condition.
This is good to know and good advice, thank you!

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Battery is fine, I’m going to pull the CEM tomorrow to check for corrosion. Currently in contact with xemodex to see if they can provide a more precise description of CEM failure symptoms, they seem to be experts regarding Volvo module repair.
 

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I have had that happen with a vehicle only once and it was a loose connection on the battery itself.


2002 V70XC, 2003 V40, 2004 S60, 2010 V70
 

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May check the CEM from above, it's a little bit faster than pulling it
But as others mentioned, I would rather think of a connector problem somewhere, because usually a faulty CEM does not shut off all power like yours (but who knows..). Many places to look at, power cable behind engine bay fuse panel, ground behind the top engine near coolant tank, small corroded wire at the top of rad cooling fan connector, small starter connector, corrosion inside black panel behind the battery. Ask Xemodex about DEM fault while there
 

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Thanks for the info. I opened the CEM up and it appeared to be in perfect condition, no corrosion or burnt solder joints.

I did notice I only have 3 volts across the large 40amp fuse on the REM, and 0 volts across the two CEM power wires.

Does anyone know if 3v across that big 40amp fuse is correct?
 

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So, I was sliding the battery out (maybe 3”) while still connected to take voltages off the distribution block behind it....when suddenly car came back to life. I’m assuming the pressure of the battery pushing against the terminal block shorted something out or disconnected one of the cem power wires....although all connections appeared normal upon inspection. I’ll also note the battery terminals were tight, so shifting it around didn’t reconnect a loose battery connection.


It’s one of those situations where everything now works, but I have no idea what was wrong, or why it’s now working.

Definitely an uneasy feeling.
 

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Intermittent open circuit is hard to locate and repair. If the circuit fails, and stays failed, you can methodically check things until you find the problem. If this was a short circuit, there would be heat, smoke, discoloration on the wiring, maybe charred insulation. This is very likely an open circuit. Since you have not found the problem, it can happen again, meaning the car is not reliable at this time. You made some progress, and now you know the bad connection is at the battery, or near the battery. Also, you managed not to spend money having the CEM analyzed, which is good. I doubt that you have a broken wire. More likely is a build of of oxidation where a connection is made. Metal oxides do not conduct electricity.
 

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With regard to the 40 amp fuse, if you measure a 3 volt drop across the fuse, it means that the fuse connections are oxidized and creating resistance to the flow of electricity. The voltage drop should be more like 0.1 volt across this fuse. Can you post a photo of the fuse?
 

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I am not a tech, just a jack of all trades and a master of none. With this said, suggest checking the engine bay wires for signs of rodents chewing on the wires. As crazy as this sounds, has happened before. Good luck.
 

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So, I was sliding the battery out (maybe 3”) while still connected to take voltages off the distribution block behind it....when suddenly car came back to life. I’m assuming the pressure of the battery pushing against the terminal block shorted something out or disconnected one of the cem power wires....although all connections appeared normal upon inspection. I’ll also note the battery terminals were tight, so shifting it around didn’t reconnect a loose battery connection.

I remember an owner had power cut and he opened the small black box by the battery, where cables go in. It was all corroded inside. Possibly water is leaking from a small rubber cap above, where the wire harness from the trunk lid is entering the trunk of the car
 
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