In the US, most autoparts stores will either loan you a reader you can use in the parking lot or read the code for you, free.

Most OBD scanners will work, but caution, there are some really cheap ones that only say pass/fail which doesn't do you any good.

Washing the engine can allow water to get into the spark plug holes and cause a 'misfire'. If this is the case, do not remove the plug, just get a rag and stuff it into the hole to get most of the water out.

Most electrical connectors will dry out in a day or two, but getting the code read and trying to delete it will give you piece of mind.
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My back feels better when I sit in a Volvo seat