Pure and simple ineptitude! Before I go any farther, the Check Engine light and Service light are 2 separate things, the first indicates trouble and the second is just a friendly reminder to bring the car in for an oil change. So I am assuming your meant to write CEL, not service light.

Blowing and ECU and not destroying the TCU is hard to do. Usually, sending too much electricity to the ECU will fry the TCU also.

It does take a while to burn 8 quarts of tranny fluid and the fluid would be almost black. Pull the tranny dipstick yourself and wipe it witth a fresh paper towel. The dipstick is behind the driver's headlight, under the air intake, about 6 inches behind the radiator. It has a yellow handle.

It is possible that the tranny had problems, but that is too much of a coincedence. If you can afford it, leave the car at the dealer - do not drive it off the lot! And call for a Volvo regional rep to look at the mess. Ask to be there when the rep arrives and get EVERYTHING in writing. The spoken work will not work at all.

"I" think that they broke it. I also think they charged you for an O2 sensor when you really didn't need one. The vacuum lines tend to crack and cause the same symptom.

Hopefully there are some reputable Volvo indys around your area, or another dealer. Once your car is "fixed", never go back!
Klaus

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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)