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Jay, Nissan Technician
Category: Nissan
Satisfied Customers: 20250
Experience:  20+yrs experience with Nissan & Infiniti Trained & Certified.Currently still working for Dealer
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2003 Altima: Crankshaft Position check engine light

Resolved Question:

I have just received a PO335 code (Crankshaft Position Sensor A Circuit Malfuction) on my 2003 Altima 2.5. Is the prob the sensor or the circuit that was reprogrammed. I have just started having a problem in the last week with it skipping while driving and my check engine light is now on. Exactly one year I took it in for a recall on the crankshaft circuit after that was fixed it started the skipping and the light came on with the code for the camshaft sensor which I replaced. Nissan said they didn't have anything to do with each other. I'm also seeing a code for PO420 Catalyst Eff Below Threshold Bank 1. I'm not sure where to start on this one. After researching on the internet it looks like this is common on this car and most have said that the dealer is telling them that the whole engine needs to be replaced. I don't understand why the whole engine would need to be replaced. Is the problem just the cat converter? It looks like both codes are very common on my car!
Submitted: 8 years ago.
Category: Nissan
Expert:  Jay replied 8 years ago.
Hello and thank you for using

You say you had the engine sensor recall performed a year ago? If you can give me your vin I may be able to assist you and answer your questions you have.

Let me know. Thanks Jay!
Customer: replied 8 years ago.
Expert:  Jay replied 8 years ago.
I see you have a Security Plus Gold on your car that expired this year 10-27-08. I also see you used your maintenance plan and maintained your car. I am guessing you have around 120 to 130k miles on your car now.

The recall you had the reprogram performed on 11-7-07. Unfortunately I do not think this recall that was performed is your problem. What most likely is going on is the crank sensor is failing. I have seen where oil actually seeps through and drowns the electrical connection. In any case, I would have this sensor checked. This sensor is not in the easiest location to check. If you want directions I can assist you.

Now for the P0420 code. I will explain this whole theory about this code. But I need to know if you are sitting down and are willing to hear what I am going to tell you.

Let me know. Thanks Jay!
Customer: replied 8 years ago.
You are right on on the mileage (125K). I've got the book repair manual which shows an ok picture of the crank sensor. Being a mom of to boys and Xmas around the corner the P0420 concerns me I sure don't want to have to replace my motor.
Expert:  Jay replied 8 years ago.
The 2.5's have known to have allot of issues. Mainly caused by the Catt converter. What happens is when the catt converter breaks up, debree of the catt get sucked into the engine and mixes with the oil and be comes like a lapping compound. Lapping compound is a like a paste that they use to seat valve by grinding them into the head using this compound. When the motor gets contaminated with catt debree it would slowly deteriorate the engine. First signs are normally burning oil. But remember, this all due to just the Catt converter. The engine it's self has not had any real problems besides that. If you have a Catt Code, I would have it taken care of ASAP. If your car is already starting to burn oil, then I am sorry to say you may need to replace the engine, but I would have it checked to confirm.

I actually have a very good friend of mine with a 02 altima. He now has 167k on his car. When he had 80k miles he asked me if there was anything he needed to due, cause he wanted to get another 100k on the car. I told him change the catt converter. So if you change the catt converter as a maintenance item at around 80k, I would say you should be ok. I hate to say it, but thats what will keep the car running with no problems. ( I know it doesn't have a timing belt, but I would treat the catt as a timing belt and change it ever 70 to 80k miles. )

Those are my thoughts. I hope the information I gave you helps. If you have any more questions, please feel free to ask. Thanks Jay!
Jay and 6 other Nissan Specialists are ready to help you
Customer: replied 8 years ago.
My car hasn't been burning any oil and the oil looks clean do you think that if I get the Catt Converter changed fast that I'll be okay or has the damage already started?
Expert:  Jay replied 8 years ago.
If your not burning oil, I would guess your ok. I would change that Catt ASAP, before it could cause damage. Also have oil changed when replacing it, just in case.

If you have any more questions, please feel free to ask. Thanks Jay!
Customer: replied 8 years ago.
Thanks for all of your help!
Expert:  Jay replied 8 years ago.
Your welcome and Thank you for using

Thanks Jay!