Check Engine Light Mystery

[jaylow]

I have a 2004 XC70 that is showing a check engine light. The code is P0497, which is well documented on this site and others. However, I've had it at a VERY well-reputed indy repair shop here in Maryland and they can't seem to find anything that will fix the CEL. They've smoked the system and found no leaks. They've replaced the leak detection pump to no avail. After having the car for a full week, they're quite frustrated (but are charging me nothing for all of their efforts, which is amazing).

Unfortunately, I'm battling the clock as the car is due for an emissions inspection no later than Jan 8 or my registration will be suspended. I mentioned the TSB that is referred to on Swedespeed but they said that it's not applicable to my car. Not sure why. I'm not a huge fan of dealership service departments, so I'm putting this out there as a last ditch effort before I succumb to a dealer visit.

Does anyone have any suggestions for anything else to try? Thanks in advance...

Jason

[Antherzoll]

P0497 -- ECM-420D --EVAP-system -- Signal too high

System isn't being vented. I'd check the purge valve and the EVAP vacuum circuit in the engine bay. Might be a faulty solenoid or a failed check valve. Don't get stuck with the Volvo EVAP pipe, you can purchase the EVAP valve separately.

Check Valve:
http://www.eeuroparts.com/Parts/5722...Valve-1275226/

Purge Valve/Solenoid (double check):
https://www.fcpeuro.com/products/vol...-volvo-8653908

More information:
http://www.volvoxc.com/forums/showth...69-purge-valve

[jaylow]

P0497 -- ECM-420D --EVAP-system -- Signal too high

System isn't being vented. I'd check the purge valve and the EVAP vacuum circuit in the engine bay. Might be a faulty solenoid or a failed check valve. Don't get stuck with the Volvo EVAP pipe, you can purchase the EVAP valve separately.

I appreciate the response. I just picked the car up. I pulled the 0497 code, but they're also showing a 4007 (which must be an ECM code, as it's not on the standard list of diagnostic codes) on the repair order.

The purge valve has been replaced (twice, just to completely rule it out), but I don't know about the EVAP check valve. Seems cheap enough...though it's listed as a V40 part. Is that the correct one?

[JRL]

How fast does the light come back after it's cleared?

[jaylow]

Typically within 15-20 minutes. The last time it was at the shop, they cleared it and it was back on before I arrived home (~15 mi). I went straight from the repair shop back to work today, also about 15 min, but it hasn't come back on yet. Since the shop notes say "Light still on, customer to take vehicle", I'm assuming that it will likely come back on before I get back home.

[Antherzoll]

The proper part listed by Volvo is the whole hose assembly from Valve-Manifold-Intake pipe with the check valves installed for ~$80. The check valves I listed are the same check valves in that hose assembly and I've had no issues with them, but the old hoses may be brittle and break.

I'd check if they are working before replacing them. Blow some air through the hoses and see if the check valve is working. Flow from the intake manifold is checked, flow from the intake pipe is checked, remove the hose from the purge valve and apply vacuum, the circuit should somewhat maintain vacuum. Blow air through the same end and air should flow out from both the intake manifold and fresh air pipe end.

[jaylow]

Update on this: the check valve suggested above was replaced and the CEL was reset. It lasted two trips (approximately 30-45 minutes of drive time) before tripping the CEL again. I got an extension through Feb 3 for my emission test, but I really need to get this fixed. After speaking to the local Volvo dealer, they just want to throw parts at it, they don't seem interested in doing any diagnostic work, and I'm frankly not sure I can afford that.

[Antherzoll]

The purge valve I previously linked is the one installed on my vehicle and FCP lists it as the same valve for the 04 XC70, V40 isn't listed, but I'm unsure how this will exactly affect the systems operation because as long as the solenoid is connected to the vacuum circuit properly and is receiving a proper electrical signal then the valve should open. Maybe confirm if the valve is operating as it should and test for voltage at the socket when the ECU is supplying it (Unsure when it's open but it can be activated in VIDA).

You can also try bypassing the valve completely. Unsure how this will affect the system and it may throw codes for a large leak but if the high signal goes away and doesn't trip then this maybe your issue.

Sorry, don't have much else to go on from behind the computer.

EDIT:
I remember datalogging the purge valve signal when I was trying to diagnose fuel ratio swings and it's a variable signal (PWM). It will gradually open from 0-100% duty cycle then gradually close like every 10mins or so (not exactly sure how long.)