P0030 Diagnostic Issue on 2006 Toyota Highlander with 3.5L Engine

Model: 2006 Uplander Fault Code: P0030 Posted: 2011-05-19 15:48

I own a 2006 Toyota Highlander equipped with a 3.5L engine. I recently replaced the spark plugs and temporarily disconnected the upstream oxygen sensor to test performance. After reassembling the system, the vehicle is now displaying a P0030 diagnostic code. I cleared the code using an OBD2 scanner, but it returns consistently—either when the engine is running or idle. This fault has not appeared before, and I'm seeking advice on possible causes and solutions. Thank you, Bill.