Can't pass safety inspection - P0447

DapprDistrctZ

Hello,

I recently got the service engine soon light. Of course the month my safety inspection expires is when it pops up. I went to a local Auto Zone and he pulled code P0447, we cleared it but several miles later it popped back up.

His suggestion was you may just need to replace the gas cap, I find that hard to believe. Has anybody encountered this and resolved this code?

You guys have never let me down insofar as the help on this forum so hoping i can get some suggestions. Thanks!

Felix 808

Code comes up as part of Evap system. If the gas cap is not sealing properly it will cause this code. Try to re-seat gas cap, buy a new one. Cracked vacuum lines will cause it as well as a few other things.

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DapprDistrctZ

Did reseat the gas cap, no dice. I'll try a new one and see if that fixes it. Really praying it's not a cracked vacuum line as I'm guessing that could be pricey to replace. Could it also have to do with the evap sensor?

SouthArk370Z

It could be several things.
Leaky gas cap is one; make sure the threads on the cap and filler neck are clean and the o-ring is in good shape. A very little bit of grease on threads and o-ring may fix it long enough to get your inspection. Check all hoses and fittings for cracks, breaks, disconnection, etc.

Using any of the major search engines, use "P0447" as your search string. Many of the hits will have troubleshooting info.
Or download the FSM (link in sig) and it will have troubleshooting procedures.

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MZ DAIZY

My experience with bad gas caps and trouble codes usually take a couple of cycles before they clear. But that was with different brand cars. Not sure how Nissans work with trouble codes.

I left the filler door open and the gas cap off a Lexus years ago. Took about 2 weeks for the CEL to go away.

Ghostvette

This is supposition of course. You didn't post mileage on the vehicle, so we are 'presuming' based on a Google search of the code. Personally, I'd replace the cap, clean the filler neck threads, apply a tiny amount of Vaseline to the new cap o-ring and call it good.

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JARblue

It would likely be a rubber evap line that cracked or came loose. Cheap and easy repair typically. I replaced a bunch of them on my 2004 Lexus recently. I just bought the proper size and material tubing and then cut them to fit.

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DapprDistrctZ

Quick question, what is the "cap o-ring" so that I can apply vaseline to it, also where is the evap line location? Thanks!

JARblue

There is an o-ring around the gas cap. This is what they are referring to.

There are a variety of evap lines. Check the FSM. See the link in SouthArk's signature.

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SonicVQ

This is a good example of why it's import find Nissan's definition of the code:
P0447 - An improper voltage signal is sent to ECM through EVAP canister vent control valve.

It is not your gas cap.

It looks to be the canister vent control valve or wiring.
This is located in the charcoal canister at the back of the vehicle.

Find and use the FSM to troubleshoot. Most parts are easy to access.
Good luck!

Ghostvette

That is correct, however, the vent control valve 'circuit' includes the gas cap. IIRC, the first step in the FSM for that code is to check the gas cap. Part of the problem is that the OP didn't give us the mileage on the car, plus Nissan sent out recall letters about that canister and that it could be damaged due to over-filling of the gas tank. The more you know.....

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SonicVQ

With all due respect:
The fault is an electrical issue (An improper VOLTAGE signal is sent to ECM through EVAP canister vent control valve.), so the gas cap has nothing to do with this fault.

The ECU monitors the voltage and current of its inputs and outputs to verify they are functioning properly.

On the 350z/370z (and G35/37) the vent value is a common failure. This is due to the valve being open all the time, except when the OBD evaporations monitor runs.

This allows dirt and water to find its way in and prevent the solenoid valve from make a 100% seal.

Ghostvette

The important part is that OP needs the FSM and needs to follow the troubleshooting steps outlined there. What he may find is multiple problems, a gas tank that has been over-filled, damaging the valve, causing erroneous voltage to be sent to the ECU. He could also find a damaged gas cap. Hell, he might even find a mouse or squirrel has chewed through a wire...

Access to a CONSULT system or a very good scanner would help diagnose the problem. EVAP system faults are generally a pain in the backside to troubleshoot and resolve. Between vacuum lines, sensors, valves and wires, it's not an easy fix.

I suggested gas cap because of the large number of failures I'd see on non-Nissan cars; as repairs go, it's relatively inexpensive. OP didn't give us year and mileage, so some presumptions have to made. If he bought an 09 or 10, it's entirely possible the cap has been damaged at some point, which will cause some odd fault codes, including P0447. Just an observation from many years of working on cars and watching the complexity evolve... You almost need 10k in electronic test equipment to troubleshoot cars any more.

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SonicVQ

Agreed, if the OP wants to fix it, the easist way is to follow the steps in the FSM.

As for the gas cap or broken line, that would cause a different code. A P0442 EVAP small leak detected.

EVAP codes are not difficult to troubleshoot. In this example, I would use a 12 volt battery and connect it to the vent valve solenoid and see if it clicks.

If it does, I would then blow in one port, energize the solenoid via battery and see if the port closes.

I have successfully used the above many times to resolve EVAP issues without special tools or a smoke machine.

Cars are easier than ever to repair, you just need to understand the OBD system. For example if you have a P0442 code, you can use the mode $06 of any good $15 OBD app (like OBD Fusion) to find out how large the hole is by looking at the test results.

This is my favourite Youtube site that explains OBD functions mostly on a VQ37VHR:
https://www.youtube.com/obd4everyone