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Join Date: Feb 2011
Location: Conway, Arkansas
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By and large the P0402 code can be a number of things related to the emissions system (and a few things completely unrelated). I'd first check all your vacuum lines and make sure you have no cracks or rotted connections. Make sure the seal around your gas cap is in good shape (though it often throws a P0400 I think, or P0402, I can't recall). Being that it's bank 1, that means the issue is in front of your catalytic converter (the O2 sensor in bank 1 is giving an unexpected reading).
Beyond those things, a faulty or clogged EGR valve (or purge sensor/solenoid) is most likely the cause. You can often take the EGR Valve off and give it a thorough cleaning (with chlorinated carb/brake cleaner and a wire brush), add a new gasket and you should be set. If the issue is the purge solenoid, I don't know of any way to remedy it, beyond replacing it.
Just as an aside, on some domestic vehicles (GM products in particular), I've seen the coolant temp sensor (SU108, most commonly) be the cause of a number of emission DTCs. I can't explain why, but they happen. On Toyota, though, I'm not entirely sure. Verify that your temperature gauge is reading accurately and radiator fans are kicking on to rule it out, though.
This isn't specific to your particular vehicle (though, being an 02 makes it even more likely), but in my experience that's often been the cause across the board of different makes and models.
Last edited by NegativeTen; 02-15-2011 at 12:55 PM.