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What year and model is this for? Thanks!
I'm showing no cross reference to a P045 code for any engine configuration for an S80. The chart goes straight from 040 to 050. Are you sure that it's a P045 code?
AH! The light goes on. That's a service message not a fault. For the life of us here in the shop, we've never been able to find the literature telling us what the heck the messages mean when resetting. VIDA has no information about them. We were told years ago that it had to do with the selections for service interval reminders set in the driver information module, but there are no instructions to that effect. Another typical one on the older S80's was "65". Nothing else, just the number "65". Even if you reset the transmission oil counter with the VIDA cart, it won't go off. The only thing I can suggest is that next time you have it at the dealer, tell them to reset the counters for fluid intervals.
Wish there was a master list that I could point you towards.
Is your "time for regular service" message staying on? The procedure for resetting is to put the key in position "I", hold the trip reset button and turn the key to position "II". Hold it until the warning light flashes. It should reset your service reminder, but after you reset it you may see that "045" afterwards. The service message shouldn't come on after that again except at startup.
If the message won't go away, you're going to have to take it to a dealer and have them perform a DIM (driver information module) upgrade. That will make the functions do what they are supposed to. You may have a software glitch with your reset function currently. Performing the software upgrade fixes it.