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Code P401 on '98 Camry

The "check engine" light on my '98 Camry 4 cylinder is lit.

The OBD show a code P401, indicating insufficient EGR flow. I've pulled and check the EGR valve and it seems to work fine (no sticking or clogging), I've cleaned the EGR tube from the manifold to the valve (by running a wire down it).

I tested the MAP sensor according to the Haynes manual. The voltage differed from what they indicated, so I changed it at a cost of over $300. The voltages are exactly the same and the MIL still lights, even after clearing the code.

I've by-passed the VSV by connect the vacuum hoses directly.

I THINK I by-passed the vacuum modulator (I connected the vacuum hoses directly from the manifold to the EGR valve).

I've tried everything I could think of, short of just changing part by part hoping to hit upon the right one. I don't know what, if any, sensor actually measures the EGR flow and if it could be bad and giving a false problem reading.

Nothing I've done gets the light to go out. I don't notice any decrease in engine performance of gas mileage. In New Jersey, where I live, a car won't pass inspection with the MIL lit or any OBD codes active.

Any suggestions would be greatly appreciated. Thanks.

Reply to
Tom C
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I disconnected battery eventually to get mine to go out. I have saved some instructions that gives you a procedure to get the light out as well that had been posted here some time ago Will repost to group as an update

The Artful Codger

Reply to
Artfulcodger

the EGR Modulator valve is bad, the modulator is located next to the EGR Valve, after changing this you need to reset the computer by pulling the EFI fuse to reset the computer ( you can also unplug the battery but by unpluging the battery will reset everything including your clock, stereo, etz) Good Luck

Reply to
skosasih

EGR modulator valve is bad, the modulator is located next to the EGR valve, replace it and clear the code by pulling the EFI fuse for 30 seconds. You will pass the smog. Good Luck

Reply to
skosasih

If you are willing to invest about $300 for a scan tool then consider AutoXray 4000 which is OBD II and works for your car.

I had P0401 on my car and it was the EGR valve, MIL was coming on only when I add Injection cleaning to the fuel. No air should flow when valve is closed, possibly the EGR valve is damaged so it does not fully open or there is a leakage in a rubber pipe at throttle or EGR that drops vacuumed pressure on the EGR valve so it does not fully open.

Read about it at

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Reply to
IceMan

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