I purchased a 1998 S70 at an auction over a year ago. Every time I get a check engine light, I attempt to pull the codes with an OBDII scanner and it shows no codes. I've used both my dad's scanner and advance auto parts. Neither could pull anything.

After getting the carfax on the car, I found that it had been wrecked. I believe the computer was replaced. I believe the scanner connects to the car because the lights fade off and back on when the scanner is synced. Any suggestions on how to get these codes?

I'm in the middle of an awful stalling / rough idle problem and don't know where to start.

 

Make sure a S70 ECU was put back in there.

 

Tech - I haven't cracked the hood to take a look yet. Will there be any documentation on the ECU stating what model it came out of?

 

Look for the bosch part number.
You can use the link below to make sure it is an S70 ECU.
http://www.ipdusa.com/Volvo-S70V70-1...-128-372-2185/
When you find the Bosch part number you will use the last 3 to match on the chart.