I was getting the P0410 (Signal Implausible Cylinders 1 - 3) and P1411 (Signal Implausible Cylinders 4 - 6) codes indicating a problem with the secondary air injection system.
Looked into the possible sources and it looked like this was going to be hard to diagnose down to one component and the likely components all looked hard to reach so I took it into my local indy. He found a leaking vacuum hose and cracked vacuum reservoir. CEL gone.
