I am calling out to my bretheren out there. I am getting involved a lot more than I thought I would be on this Pathfinder.
P0450 FTP Pressure problem & P0446 Vent problems fixed, now P01447 returns intermittent.
Parts Replaced:
According to Tech, FTP sensor (known as Boost Sensor) near tank was stuck at 5 volts. Voltage did change with new sensor 3.3 volts static. Found charcoal in purge system.
My questions? Why does this code P1447 keep returning? Also, what scanner has bi-directional control for the Vent solenoid and bypass valves? My Snap-on and Autel scanners do not have any bi-directional for any solenoids in the rear (vent & bypass). The Snap-on scanners do have 3 bi-directional (functional) tests for the Evap system, two of which seem to be the same test for the purge Volume control which seem to work and one test for the Purge, which doesn't seem to actuate anything in my testing, cannot hear any solenoids click in front or rear.
Diagnostic Steps Performed:
What I found was this: Charcoal in the purge system, canister has lost it's abilty to keep charcoal in it. Blew out vacuum hoses from front to rear. Took canister off vehicle and dumped as much charcoal out as possible and put back on vehicle. For now, added clear fuel filters between canister and purge hose system. No charcoal has shown in these filters yet. I will not change the canister till I know the whole story asthis is the kind of job that gets expensive, you know the kind of job that customer leaves at your shop after they realize they shouldn't have authorized the work...
Testing under hood:
Purge volume control solenoid is bleeding vacuum at 0% command, possibly charcoal stuck in valve. Purge volume control valve seems to respond to bi-directional control from Solus Ultra and Verus.
Purge cutoff solenoid functions when grounded, passes vacuum to purge cutoff vacuum valve, and allows purge vacuum to flow when solenoid is grounded. This valve seals front of system under hood so no purge leaks to tank, confirmed no vacuum increase in tank with Vent solenoid hose pinched off when valve does not receive vacuum from solenoid. No Bi-direction control to the Purge cutoff solenoid. Have not confirmed if PCM is capable of actuating this solenoid yet.
Testing in rear:
Vent solenoid has power and closes when grounded, and seals, confirmed by blowing into vent, when closes will not pass air. No bi-directional control for Vent solenoid. Bypass valve, has power and will allow flow when grounded. cannot confirm if white plastic "cut valve" works or not. I need a test procedure for that piece. I remember back when I did a lot more Nissan Evap, there was procedure for testing that valve, don't recall how to do it now.
33003001.BMP
Fuel tank pressure remains at 3.38 volts and voltage will rise to near 5 volts when vent solenoid is pinched off due to pressure build up in tank and will drop to 0 volts when purge is allowed to flow. Also when high vacuum is pulled into tank, pinching off purge hose in front keeps vacuum in the tank indefinitly, so at least that part of tank is tight. When driving, I don't think I see much change from 3.38 volts
Not sure what to do next except attach scope leads to all control lines on all solenoids. and monitor fuel temp and fuel tank pressure.
Also, I did not energize the bypass solenoid while there was vacuum held in tank, to see if fuel tank pressure changes. Will do that tomorrow.
So, who is a Nissan Evap Guru out there? Are you familiar with all these solenoids and vacuum valves?
Thanks in advance, Bob
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