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Check Engine light

I have 1996 Toyota Camry 4 cylinder engine with check engine light on since 2007. I took it to O’Reilly auto parts and they checked it and the trouble codes are P0441 and P0401. The report indicates about 50 possible fixes. Can some one narrow down please. The car runs fine except every year I have to go through hard time for emission inspection. By the way, I have replace the egr valve.

What do you do to make it pass inspection?

EGR low flow…You probably need to clean out the passages that feed the valve…This can be difficult. Are you simply re-setting the light just before your emissions test? If that works, then just keep doing it…EGR problems, as you have discovered, are not a critical issue…

Usually resetting the light will not get you through inspection because the system may detect a ‘not ready’ state as you haven’t been driving it enough. It only works if the condition is intermittent and you can get it to show ‘ready’ at time of inspection.

P0441 is an indication that you might be overfilling your gas tank. If you don’t already, you should stop filling when the handle clicks off the first time, do not “top off”. Gas comes out of the ground at around 60°F and in the summer, it starts to heat and expand. If you overfill, raw gas can be forced into your canister and purge valve.

As for P0401, Caddyman is right. It can be the valve itself or one of the ports feeding it. Spray carburetor cleaner usually can clean them out enough to keep the light off for awhile.

I can post using Safari now, yeah!

Many conditions that set the check-engine light also reduce your gas mileage. If the EGR-related code is one of them, I’d hate to think how much money was spent unnecessarily on gas over the past five years.

EGR valves reduce an engines efficiency by lowering combustion temperature…If fuel mileage is affected at all, it will be improved…Engines tuned for maximum power and efficiency have no EGR valves…

I can’t agree with that. What EGR systems do is prevent engine damage by preventing cylinder temps from spiking when the engine is under load. The don’t reduce efficiency, rather they allow the engine to operate at its most efficient the bulk of the time by preventing damage at those times when the optimum conditions might cause unintended consequences.

Everything has tradeoffs. Getting the most complete combustion, the lowest emissions levels, requires that an engine operate at full temperature. The problem is, that temperature can spike if you then floor the gas pedal. To prevent that from causing preignition, something needed to be installed to counter that tendency. The EGR system does that by replacing a bit of the oxygen in the intake air with inert exhaust gasses, lowering the spike.

When you floor the gas pedal, the EGR valve is closed to provide maximum power. EGR systems have nothing to do with preventing engine damage. Their purpose is to limit NOx emissions by lowering combustion temperatures. They only function at mid-range throttle positions. They are closed (turned off) at idle and full throttle…

You are correct in that it shuts down under WOT, but in addition to reducing NOx gereration it also protects the engine from pinging and preignition. It accomplishes both by keeping cylinder temps from spiking above 2500F.

But, I cannot agree that it reduces the efficiency of an engine. By preventing an engine’s cylinders from getting too hot, it allows the engine to operate at the higher temperatures that promote complete combusion. IMHO it allows the engine to operate more efficiently. Between the thermostat and the EGR system, an engine is allowed to operate in its optimal temperature range without damage and without excess NOx generation.

Since you’ve replaced the EGR valve and the light hasn’t gone out – assumng CEL was properly reset – it must be something which congtrols the EGR valve that remains faulty. The EGR is regulated by vacuum and probably the ECU controls a vacuum switching valve too. You might still have a vacuum leak, or the ECU or the vacuum switching valve has failed.

Unless you want to find the Toyota Service Manual for your car and start studying, I’d recommend finding someone experienced in Toyota emissions systems to help you out. You need some car- specific expertise on this one I think.

Also Google your make/model and the trouble codes, sometimes that will lead you to somebody else you has already solved your car’s problem.