98 V70 LPT Real Odd-Ball P0455

Post by **rmmagow** » 02 May 2014, 08:15

Yes, I know what it means. For months and months. all winter in fact, My car ran with no codes and all systems in READY state. Last week I ran the fuel level down somewhat below 6, was driving it a bit hard and the CEL went on when I came to a stop and let it idle for a few before shutting down.
Long story short, if I never let the fuel level drop below 6, no CEL, below 6, stopped and idling, CEL and always the P0455.
I plan to go through and replace any hoses and maybe the round valve at the radiator housing, the gas cap is maybe 1.5 years old and Volvo and looks good.
I don't understand the odd behavior, any ideas?

TrstnBrtt · Post by **TrstnBrtt** » 02 May 2014, 10:10

I've noticed my S70 does it when fuel is getting low too... I just reset the code

Post by **rmmagow** » 02 May 2014, 11:49

Yeah, me too and it's not a problem until inspection time. My car takes months and 2000+ miles to reset to ready. But, yeah, it certainly isn't a serious problem.

Post by **deepsouth** » 02 May 2014, 12:10

Here’s my understanding of the EVAP system (someone please correct me if I’m wrong).

There are two solenoids in the system. One controls the fuel vapors (purge valve) and the other is used for venting the canister (shut-off valve). There is also a fuel pressure sensor (I took a photo of this in my write-up) at the fuel tank.

The purge solenoid has two lines (and an electrical connector) attached: one to intake manifold and the second to EVAP canister. The electrical connections go to ignition switch and the other is grounded through the ECU. When the ECU grounds, it opens the valve allowing vacuum draw from EVAP system.

The second solenoid (the shut-off) is usually open. The ECU tests for leaks by closing off this “shut-off” valve (which seals the system) and can then test for leaks via the purge solenoid and the fuel pressure sensor.

Once the shut off solenoid is closed, the purge valve opens and allows the vacuum to draw air from evap. The ECU then receives info from the fuel pressure sensor and compares it to spec values to determine if there’s a difference (aka “a leak”).

There are many circumstances and hoses that can throw the various codes (P0455, P0442, P0440, etc). Some of those I documented in my write-up, the other involve the sensors and solenoids not doing their respective jobs. As for why it only happens on your vehicle on less than half a tank, I’m uncertain but it could be related to when the ECU runs the tests and how much vapor is built up.

Post by **rmmagow** » 02 May 2014, 12:30

Deepsouth, I'm going to use your writeup this weekend to have a good look around. This past winter I bought a sort of remote viewing camera thing from HF and this is a good thing to help peek at the top of the canister. Actually, the pictures you show make me think pulling the canister out for a good check will be fine. I know the largest of the three hoses on top was broken and I did a little blind magic to put a tube in place and duct tape it back together. You write up will help me figure that out and replace the line. The line that leads to the fuel tank, would blowing on that be a decent test to see if it leaks at the tank? I'm figuring blowing on it should get to a point where I can hold the pressure and it shouldn't bleed off. A little cigar smoke can go a long way to chasing this down too and damn, I need a good cigar and a beer!