2006 Toyota Sienna Codes PO 351-356
My 2006 Toyota Sienna has codes PO 351-356 with the check engine light one
and failed emission test. Despite this, this vehicle drives like new. What could
be the actual problem before I start spend for repairs.
Since this is happening on all 6 ignition coils, I suspect you've got an intermittent wire harness issue on the power side of the circuit. Check for battery voltage on the red wire at each coil connector with the key in the RUN position. Wiggle the harness to see if it changes. If it does, look for an intermittent open condition.