P0402 & P0420 got two new codes this morning.

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Oct 2, 2009
Mission Hills, Kansas
Got two new CEL codes this morning. P0402: EGR Flow excessive detected: Trouble Areas: EGR valve stuck open; EGR VSV open malfunction; open in VSV circuit for EGR; short in EGR gas temp. sensor circuit; ECM. P0420: Catalyst system efficiency below threshold: Trouble Areas: Three-way catalytic convertor; open or short in heated O2 sensor circuit; heated O2 sensor

Spent about three years living with CEL light and a short in the upstream O2 sensor wiring. Fixed that about a month ago and have improved performance, mileage, and consistently running closed loop.

Any ideas about the cause. Thinking may simply have worn out Cats.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

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