We recently purchased a 2004 XC90 170,000 miles and are having strange things happen with it. Started it up at the guys house and it drove fine. Purchased it and drove it about 15 min down the road for dinner and it wouldn’t start initially. Realized the key had to be in the plastic case (it’s broken and the blade had fell out) and it started finally. Took 90 min to get it started and it that time we unplugged the battery and did lots of finagling. Initially when it started it ran very rough, surging at idle, sputtering and would barely move. Shut it off and restarted it and it ran perfectly the 90 min home.

Next day it started very rough again with the sputtering and surging. Checked the ignition coils and found one to be bad. Replaced it and it ran perfectly again! Eureka. Shut it off and basked it my figuring it out. Well 20 min later I started it again and back to square 1. This time it had zero power. Couldn’t get it above 20 mph. So I replaced all the coils and all the spark plugs and didn’t help. This morning I took it (limped it) to the local mechanic and here are the codes.

91b7 Electrical control unit

3000 Engine speed sensor

1300 Boost pressure sensor

Coil 3

Coil 4

Coil 5

Coil 6

130a boost pressure sensor

3340 Control module internal malfunction

No idea why it says coil 6 if there’s only 5 bug that’s what it says. Any help would be greatly appreciated. Cheers!