P 0420 Cadillac Sts. To eliminate things one by one, we replaced all spark plugs with new. Check the "Possible Causes" listed above.
FS/FT: Cadillac Seville STS on 20s. fully loaded. Mid. Tennessee - Honda-Tech - Honda Forum ... (Jeffery Reyes) I need to complete more drive or ignition cycles. It should be fine to drive. Short Term Fuel Trim on both banks is close to normal (maybe a little rich).
It happens at stop lights and while waiting in drive thru lines, dealer says it is normal with the high performance sts-v engine that I have. I need to complete more drive or ignition cycles. Visually inspect the related wiring harness and connectors.