EcoFix OBD2 Reader
Tells you what the warning light actually means.
$49.97
Free shipping, and 30 days to send it back for a full refund if it isn't right.
What it's good for
Reads the code
Pulls the stored fault code and tells you what it refers to, instead of a warning symbol and a guess.
Plugs straight in
Into the OBD2 port under the dash. No tools and nothing to disconnect.
Worth one garage visit
It pays for itself the first time it turns out to be something you can sort yourself.