So ran the DTC mode and came up with numerous DTC codes. Haven't used an OBD reader, just the onboard diagnostic. Thought it was fuel cap so replaced with new OEM unit. Went off for a bit but now back on with those codes.

Oddly had the car at Trani shop 2 weeks ago bc Urgent trans light was on. Had It rebuilt in summer so figured it failed again. Transmission shop found no trans issues but reported many codes (ECM, wrong software, etc) So many that they figured there was a gremlin since it runs fine then and does now. Talking with some of their techs they proposed a charging issue may trigger multiple error codes. Never heard of this before? Battery is 10mos old and was 80% charged when I checked it today and plugged the charger in. It's about -3 today so not arctic cold.

Any thoughts before I start pulling things one by one?

Thanks and Happy New Year
Mike

I would stop by a parts store and check the alternator and battery. Yes, a low battery charge can cause numerous errors to show up. This is the XC90, correct?

Check the wires at the alternator and make sure the cables are tight at the battery. You have a severe problem if the battery is only at 80%.

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My name is Klaus and I am a V♂lv♂holic

Thanks I'll stop by a store that can test batt and alternator and have a look at cables. The 80% was a guesstimate based on charge indicator appearing on batt charger, which is probably not very accurate.