That 402 Excessive EGR Flow error

Hello,

I got the dreaded 402 excessive EGR flow error and can't track it down.

I've replaced the EGR valve, the temperature sensor and the vacuum modulator. I've checked all the vacuum lines.

This is the 2.4L engine with no mods, bone stock, with new plugs and filters.

The CEL comes on right away (after 6 or 7 engine warm/cold cycles) and gives me two of the 402 errors.

Back in the winter, when it wasn't warmer than 20° (this is Montana), the CEL would stay off for a couple weeks at a time. But now, since it's in the 60s, the CEL comes on right away.

My gas mileage is right around 20, and that's with 240K on the engine. The engine is smooth at cold start up, at idle, and at highway speed.

This is also a California truck, so it's got some extra emissions controls on it, or least that's what people tell me are installed on California trucks.

I don't see any exhaust manifold leaks, regarding what other people posted about.

Any ideas?

Thanks.