# 97 Pathfinder P0440 and P0446 codes



## Hal2 (Oct 14, 2015)

Hi, I have what seems to be a common problem, but the usual solutions are failing me. I have a 97 Pathfinder that is throwing two CEL codes, P0440 and P0446. Initially, I was just getting the P0446 code. Turned out that the evap vent control valve was corroded and stuck. I have now replaced the old charcoal canister (which was leaking), blown out the hoses, replaced the evap control vent valve and replaced the gas cap. However, I'm now getting both codes after a couple of days of driving. The brand new evap control valve seems to be working properly (tested with 12v - opens and closes), and there is voltage at the plug when the ignition switch is turned on, so wires are intact. The gas cap seems to be working, as there is a pressure release when opened. I have also checked for leaks in the hoses, which seem intact, but I have not done a smoke test to check for leaks. Also the P0440 code comes up first, followed by the p0446 code a few minutes later. I would think that the the vent control valve must be working in order to run the pressure test for it to fail. 

The cause of this really has me stumped. Any suggestions appreciated.

Thanks,
Hal


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## smj999smj (Jan 1, 2006)

Well, the test fails when the ECM attempts to test the system and does not see any change in the reading it gets from the evap system pressure sensor, so, that it goes ahead and tests the system and fails has no bearing on whether the vent control valve is working or not. Moving on....when the canister lining fails and dumps charcoal into the evap system, it can be a real job cleaning it out and just one, tiny bit of charcoal left in the system can create problems. You may or may not be aware that there is a Nissan TSB that instructs how to properly clear out the system if this failure occurs. You may have to perform this procedure several times in order to get every last bit of charcoal out of the system. Smoke machines are great when working with evaporative emissions systems, but, unfortunately, they are expensive. Cheapest one I've see was around $800.


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## Hal2 (Oct 14, 2015)

The purge control valve had a couple of charcoal particles in it when I first checked and cleaned it a few weeks ago. When I blew out the line, a few more came out, but have not seen any more since and I've checked several times to be sure. Could a bad pressure sensor be the problem? 

Thanks,
Hal


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## smj999smj (Jan 1, 2006)

It's possible.


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## Hal2 (Oct 14, 2015)

Found the issue. It was a crack in the plastic "y-connector" on the hoses connecting to the canister. Replaced it and all is working correctly, with no new codes. I originally assumed the P0446 code meant something was wrong with the vent control valve. Turns out just a small leak can be the only problem.

Hal


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