I'm chasing ocassional P0440 OBD code. Did some research and understand what can cause it. What I don't understand is this, Once EVAP system is under pressure which component will actually detect the leak? I don't think it is the purge valve...It obviously has to be some electronic sensor. Is there one in or near the gas tank?
This is why I don't think it is the purge valve...Let's say there is a major break in one of the vacuum lines that's not allowing pressure to build. How is that different from time when purge valve opens, or is stuck open? Result is the same, lack of pressure...
Or let's say purge valve is stuck closed, and we have a constant pressure. Why would CEL get set??? Does this mean CEL is only set if the purge valve is stuck open, or if ther's leak in the lines? Aspirin anyone???

Moe, there is a leak in the line. Somewhere. Wether it is a cracked plastic elbow or a stuck valve or a bad relay, the solenoid cannot close properly which triggers the P0440.

This is the bane of errror codes. Multiple reasons can cause the same error, just like vacuum leaks will mask an O2 sensor problem or be the cause of it. The only way a car company could be more specific is to have sensors everywhere and then they would need to install sensors for sensor failures. Kinda like NASA.

You need to pull off the right rear wheel and check the cannister line elbow. If it looks to be good, then check the cannister connections in the left front of the car, then check the check valve, then...

Klaus
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Proud owner of a 220S. If I had more room, I would have more Volvos.

I don’t see the reason for installing ‘sensors’ that generate erroneous
or misleading information. P0440 can be triggered by a host of
different things. This code is very generic and does not effect the way
engine runs. Some folks have gone
to their dealers numerous times and still have this code.
The only real CEL of value is the one pointing to MAP of MAF sensor,
as these can dramatically affect engine performance. Heck, engine won’t
even run…But, all the other codes are crap generated only to make
profit for mechanics…and parts sellers…

Relax Moe, the environmentalists are the ones that created P044x codes, not the car makers. The same people that created the PCV way back when all sorts of pollutants were created by the IC engine. The gasoline evap system is the reason you should never smell gasoline in your closed garage.

I realize there could be two warning lights, or even a bunch, to distinguish between a real engine problem and other problems not engine performance related. But, then no one would get their 'other' light turned off because it does not affect drivability; similar to the service light. I had a 1992 Mazda MPV that turned on the CEL at 80,000 miles... to get me to a dealer so the emission controls could be inspected and charge me $250 to turn the light off for another 80K miles. Needless to say, the mechanical tripper on the odometer was removed by me.

Use some TB cleaner and try cleaning out the SAS valve and see if that makes a difference.

Klaus

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Proud owner of a 220S. If I had more room, I would have more Volvos.