# check engine light - code P0450



## sticksout (Oct 24, 2006)

*Here is the story:*

I've got a 99 Maxima GLE with 103K miles. About three weeks ago my check engine light came out. Took the car to Advanced Auto to get the code read and it turns out it was the Knock Sensor and the EVM Sensor. Took the car to the shop and they replaced the Knock Sensor, but the light still wouldn't go off and now it is throwing the Evaporative Emission Control System Pressure Sensor Malfunction (P0450). So I left the shop with the EVAP Pressure Code not being replaced as the guy said that it won't hurt the car to drive it w/the sensor blown but that I won't pass VA emissions.

*Questions:*
Is this a common problem?

How much am I looking into for repairs/part cost?

With the P0450 code blown, would it affect or result in the fact that when I get gas, the pump keeps kicking on me so I'm constantly fighting with it to find the sweet spot (this started happening about the same time the check engine light came on initailly, but I attributed it to the specific pump)?

Can anyone offer advice on why the gas pumps would keep kicking eventhough the tank is nowhere near full?

Thanks in advice.


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## MaxFreak87 (Jul 20, 2006)

I have a simple question how much did they charge you to change the KS?


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## sticksout (Oct 24, 2006)

total came to $573.16

breakdown: $196.77 knock sensor (Advanced Auto was selling it for $188)
20.00 coolant (2 bottles)
28.74 intake manifold gasket
2.00 clamps (2)
5.50 cleaner
300.00 labor ($75/hr)


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## mech361 (Jul 31, 2006)

The knock sensor on this car will set a code, but won't turn the check engine light on. Sounds like some kind of blockage in the evap system, not allowing the tank to vent during refueling. You might want to check the water separator at the rear of the charcoal cannister.


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## fgoodyear (Mar 18, 2005)

I was told by my Nissan dealer that the knock sensor code is a junk code and they very rarely change a KS because they never go out. Whatever the other code is, is what the problem is. The dealer said to ignore the KS code because it willl not kick on it's own. I have a problem that the downstream O2 sensor intermittently kicks a code and it ALWAYS kicks the KS code also.


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## Jeff (Oct 17, 2002)

I know of at least 5 ppl within our Nissan car club that have changed out their Maxima's knock sensor due to poor mileage...including my own. This is out of about 20 ttl Maximas.

If that is rare then I'd hate to see what a lot is.


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## GKronfle (Jun 22, 2009)

Did you figure out what the problem was? I'm having the same issue! Code P0450 and the gas pump kicks back when refueling... Can you help out?


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