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98 toyota camry emissions night mare

have a 98 toyota camry with the 4cyl automatic and im haveing a helluva time with emissioms have replaced all emissions components mechanical and electric from charcoal canister to egr valve and all switches and switching valves in between and i am still getting codes P0401 and P0402 …Help!!!

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Did you clean out or replace the EGR plumbing and ports?

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I think in our state you can get a waiver after spending so many dollars.

Have you tested/replaced the EGR vacuum modulator?

This is what controls the operation of the EGR valve.

Tester

P0402 usually involves the O2 sensors or the catalytic converter. What has been done with them?

https://parts.olathetoyota.com/p0402-code-toyota

Tester

Sorry to hear that you or someone else “shotgunned” this repair

I dont see it listed so i shall ask… did you replace the VSV ? Variable switching valve… it is well known to cause 401/2 codes and is often overlooked or mistakenly replaced with inferior aftermarket vsv units… it needs to be an OEM Toyota part. I believe it supplies varying levels of vacuum to the egr system or the egr itself… i forget. Cheap copies arent able to vary with the accuracy of the oem units…and wind up supplying too much or too little… when “just right” was needed. Many times they will cause the engine to stall bec they peg the egr open when its only sup to he partially open. Anywho…

I just had a rash of 97-99 4cyl Camry’s all with 40x codes… and on all of them the solution was a new Toyota oem VSV… This was the solution 3 out of 3 times…after of course verifying all other components that were in play like the EGR and vac hoses etc.

This valve is very often overlooked and to be honest i was well UNaware of its existence until a bunch of 4 cyl Camry’s decided to come to me all with 40x codes… The valve is a proper PIA to get to and when replacing it check all the rubber vac lines or simply replace all the lines to be sure they good…oem quality vac lines will last like no other as there is a vast difference in rubber quality in hoses… cheap hoses use cheap materials… just fyi

But that is what i have found solved the issue.

Unfortunately after “shotgunning” anything… you honestly dont know “where you are at” with the repair… but if u did NOT replace the vsv… i strongly suggest you look into it.

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420 is the code that brings the cat and o2’s into play… not 401/2 i think you got the digits switched up from memory. Lol. Happens to me all the time

???

Read my response?

Tester

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LOL… NO … what i just did was read what you quoted as if you responded. Omg im losing it…or my vision or both.

Disregard Mr @Tester… I’m just flaking out

It did seem odd that you would suggest what i thought u suggested… i did think that… but those werent your words at all

Ok im goin to bed

p0402 is excessive air flow

my year doesnt have a DPFE

no p0401 and p0402

yes has been replaced

Ok… i just hope you replaced it with a Toyota part. The VSV is one of those items that u need to use the oem part… at least this is what i was strongly advised… the aftermarket units seem to cause those 401/2’s to return

So just a thought. Your issue isnt usually too difficult to solve as long as you go thru troubleshooting and verifying carefully… no skipped steps or assumptions… and im told… no aftermarket vsv in particular

Apologies. Never was good with math and the days are long.

Show me where I typed that your vehicle had a Delta Pressure Feedback EGR system?

https://www.toyotanation.com/threads/how-toyota-egr-vacuum-modulator-works-everything-you-need-to-know.1623818/

Tester