前几天我在这里发帖求助，关于 2000年 Toyota Camry engine check light亮了，查了Code是 P0401，在这里得到热心网友的好多建议帮助，结果还没等我采取措施发现那个灯自动灭了，很开心，不过好景不长，一两天后又亮了，我观察了一下，加满油后开150迈左右（大概不到半缸油）灯自动熄灭，再开到 200 迈左右 灯又亮了，我很好奇又试了一次，加满油再开，同样的情况又发生了，就是亮着的engine check light 每次在加满油后 开到 150迈左右熄灭， 至 200 左右迈重新亮
请问群里有朋友遇到过类似的情况吗？这对诊断engine check light的问题有帮助吗？
"So, my P0401 error code seems to be the gas cap. I replaced it this morning. Drove about 50 miles in two drive cycles. Got back in the car a 3rd time and the check engine light did not come back on. I have driven it twice now with no check engine light. It was a $22 gas cap from the Toyota dealer. I don't know if that is your problem or not. The dealer service department person told me bluntly that this was not my problem and I was wasting my money buying this part. If the gas cap was the problem it would produce another a different error code. But, for my case, that doesn't appear true. I will keep driving it and we'll see."
换后，断开电瓶，踩刹车，按无电喇叭消码；再连上，开60 miles 以上（一个circle），如果换了灯还亮，第二步，去 dealer 买一个正宗 EGR valve，然后找一家车铺换，dealer 人工一般翻倍。
go to Amazon to but a car monitor tool to reset the code.
油箱里的真空度到了一定的时候fuel tank cap没能让外面的空气进去，平衡气压。
The code P0401 is listed among other possible codes. The repair again involves cleaning the EGR ports. Toyota Camry/Corolla: In Toyota Camry with the 2.2L engine, the code P0401 was often caused by a bad VSV (Vacuum Switching Valve) for the EGR, located under the intake at the back of the engine.