Hi- my first query here. I am in the correct forum- I USED to drive a 94 850. Now a 2004 V70 SW with 125K miles.
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...also the AC is blowing warm air- this is what I noticed first. Then the gauges and the warning. After stopping and looking at the likely fuses,
it started up fine with only a warning about a low beam being out- which had been out for a couple of days.

After doing some searching: ABS module? But what about the fact that it started right up with no warnings except the light bulb?

At no time did the car's performance seem to suffer.

I'd be grateful for any ideas or reassurance that the car is OK to drive.

Thanks, Clay

 

if it happens when a weather is war or hot, the ECU might be overheating. Check the fan in a ECU box. Also try AC with most vents into the interior closed - it helped my case...

 

could be a connector into the CEM. I believe on your model its under the dash on the passenger side (on other models its on the drivers). You can probably find a Youtube vid on CEM (central electronic module) issues/ replacing but it sounds like a loose connector.