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My car has been throwing cide 0171 intermittently for about 6 months. The CEL would go on for a few days then shut off and so I didnt look into it any further. My camshaft sensor went out about 2 weeks ago and it had since been replaced. The check engime light went out again after the replacement sensor was installed. Approximately 3 days after replacing it my CEL came on again, this time reading 0420 in addition to 0171. It has stayed on ever since. I was told to replace the downstream o2 sensor, I want to make sure that is most likely the issue and also it would help if I knew what those codes meant- especially in combination with each other. Secondly I would really like to see a readable diagram under the hood and the undercarriage. Nothing worse than going in blind to try and fix something!

Any info I can get is much appreciated! Thanks guys!

Vehicle: 2005 Nissan Altima 2.5

1 Answer

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The most common cause of the problem is the Mass Air Flow (MAF) sensor. You could try clearing the MAF and changing the air filter first. If the problem persist, the next step is to replace the Oxygen Sensor.

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