2006 XC70 CEL question on reset

[scot850]

The CEL comes on from time to time randomly with the code for minor emission leak. I usually reset it and it stays of sometimes for several months. I've replaced the fuel cap and cleaned the cap and pipe threads for the fuel pipe and cap.

Simple question, does the CEL reset on this car if the problem does not persist? Started/stopped the car half a dozen times running errands yesterday but it is still on.

On of the experienced mechanics I know at the dealer said if the CEL comes on with under a half tank left, then it may be the emissions check valve failing as it can't hold the pressure (I think that was what he said). Problem is since being told that, the problem can happen from 2/3rds of a tank or most times not at all. Could be temperature related as we have huge temperature swings this time of the year (-44C 2 weeks ago, +15C today).

For now I will leave the light on as the car is due a service shortly and I'll get the dealer to check it again as they had no luck the last time (I'd switched the CEL off a week before).

Thanks,

Neil.

[jimmy57]

The self reset of codes happens by seeing no problem for a few test cycles and then the light goes out. The code is still there for 40 or 80 warm up cycles after light goes out. The 40 or 80 count is set by EPA regulations and I can't cite which are 40 and which are 80. Test cycle varies but for fuel tank leakage it is several longer drives with a several hour key off period between. Also fuel level for any qualifying drive cycle must be between 15% and 85%. I would think the J hose on canister is not due to be cracked on an 06 cold weather climate car but it should be checked. Smoke testing is THE best way to find small leaks the system has flagged.

[JRL]

J hose on an 06?
You need to get the code read.
A good guess would be your leak detection pump is failing (common on later P2s)

[scot850]

Thanks guys. Most of my driving is city, but Calgary is almost 25 miles across. Having said that, my trips on that day, were mostly 5-10km at longest. It sounds like it is unlikely I will have the light turn off by itself. I'll have the dealer do the smoke test to be sure all is good on the leak side of things.

JRL, many thanks. What you mentioned is what the mechanic I spoke to said. He also said it is common on the P2 models.

Looks like that will be on the next part order.

Thanks again,

Neil.

[jimmy57]

06 doesn't have a J hose but it has an elbow and some connector hoses.
I have had many LDP issues but I haven't run across one myself that gives small leak code. The canister close valve is part of the LDP and that could leak and give small leak code. Most LDP failures occur during the calibration part of the test and give another failure code other than small leak. That is the reason Volvo has had software upgrades to address the problem. Their bulletin on the problem specifies to upgrade software before LDP change when the code is for the failure in calibration part of the tank leak testing. Cold weather you get your way may give different failures.

[scot850]

Many thanks jimmy57. Having thought of what I said on my last post on this subject, I believe I remembered wrongly what the mechanic said to me. It is not the pump but the valve that fails not allowing the pump to draw down quickly enough during the test cycle. He said it was a $40 item, whereas the pump is >$130.

Appreciate the other info on the software upgrade.

Not sure the weather is the issue, but we also got the yellow warning triangle coming on saying fuel cap is loose (?). Mind you, can't recall seeing that since I replaced the fuel cap. Having said that, my wife is the one who drives the car most. She is pretty good at reporting stuff that is not normal on the car (took years to train, but she knows I get grumpier if I don't get told).

Thanks again,

Neil.