VNT & TCV test in VIDA - ECM 6805 (again!)
 

Hi again guys!

You've maybe seen my recent post resulting in a successful replacement of my servo unit following fault code ECM 6805. All was well for a few days but driving along with the window open a couple of days ago I heard what sounded like a hose or connection blowing off and the "engine service required"/ ECM 6805 re-appeared driving to the shops.

https://www.volvoforums.org.uk/showthread.php?t=132443

I've been working my way through this thread above which is really useful though sadly the pics are no longer available. Is it possible to get them again? Just for info, the output from the vac pump is good, as are the hoses between vac pump, turbo control valve and the engine pads. I bought a new TCV recently as the response from the TCV output was sluggish on the vacuum tester gauge and I suspected this was faulty. The new one is behaving just the same though. I'd like to test the VNT governor using VIDA but cant find where the test process is. Can anyone help please? I have a 2003 XC90 D5 by the way. Also I've had a really good look but I cannot see the vacuum actuator on the turbo, so any help with location would be much appreciated!
Cheers Tony

Hi guys just thought I'd post an update. I've started fault tracing again and have bypassed the control valve and engine pads taking the output from the vacuum pump directly to the vnt governor. All is well. I'm puzzled because the hoses and pads are all holding pressure. I'm thinkin. I'm thinking there maybe a fault with the electrical signal to the control valve or bad connections. I can't think what else it could be??

So...... for the first time since bypassing the control valve and engine pads, the "engine service required" message popped up. I pulled over, switched off and restarted and everything was fine again. I obviously have something else on the edge of breaking down. More investigation necessary! :-)

Check any rubber hoses on the induction side of things especially turbo related, they will need a rub of a finger to detect splits but the giveaway will be oil residue where there should be none.

Thanks SnineT. Both hoses from the intercooler feel quite soft but not apparently leaking. Some months ago when I started having the ECM 6805 code I found the rubber elbow into the VNT governor was perished. I did a repair with some fuel hose and when I inspected that again yesterday the hose came away in my hand. I temporarily used a smaller diameter hose and the car went well. I've just bought the proper elbow from Volvo so am hoping they will solve my issue. I'll keep you posted. I might replace those intercooler hoses anyway......but one thing at a time for the sake of diagnosis!

Morning all! So yesterday I fitted a new elbow on the input to the VNT governor and I also fitted a new one on the output nipple of the vacuum pump as they're the same. Performance of the car was strong on a test drive after so hopefully that's it sorted. It's maybe worth noting all the bits I've replaced which have thrown up the ECM 6805 code:
1. Unblocked the VNT governor
2. Replaced the two rubber elbows
3. Replaced the front engine pad
4. Replaced the brake servo unit
5. Replaced the rubber connector on the input of the TCV valve

I think it will be worth replacing all the hoses and connections in the vacuum circuit soon anyway.

Hi guys. The car has been performing ok since fitting the new elbows but I thought I'd post this video of a vacuum gauge on the output of my turbo control valve and compare it to SiRobb's video of the same thing.

https://youtu.be/qvpjhN-2DdI

https://youtu.be/2yeT9Qo_KRM

The conclusion I came to was I had a faulty solenoid valve but after trying a new one, that behaved identically. Any ideas why mine is more sluggish to respond?

On SiRobb's video the relevant part starts just after 6 minutes in.

So guys over the last three days I've had a recurrence of the "engine service required" but in specific circumstances. I've been driving it to work with no issues. It sits all day in the car park. Pulling out of work to drive home the error message pops up. I pull over, switch off and restart immediately then the car performs perfectly normally with strong performance. I think that's an electrical issue rather than a vacuum issue and I'm suspicious of my slow responding TCV. My mate has an oscilloscope...... I'll get the signal to the TCV tested next week.

So..... I couldn't access my mate's oscilloscope as it's wired into an installation and I couldn't get the car close enough! So we used a quality multi-meter and got results which were different to what VIDA says.
1. At ignition on the engine pad valve gets 12V
2. With the engine idling it gets 14V with the alternator charging
3. Above 1100rpm approx the voltage drops to 10V.

We hooked the pad valve up to 12V and it clicks as it should.

Our conclusion without a good reference point was that the PWM signal is probably working.
On one occasion during the test when turning the ignition on, we got zero volts at the plug but switching off and on again we got 12V. Maybe I've got a dodgy wire somewhere?
Yesterday leaving work again, pulling away the fault returned. I pulled over, restarted and everything was fine. Today before leaving work I turned the ignition on then off again then started the car. No fault and the car pulled well. I'm going to investigate the wiring next.

I thought I'd post an update to my still unresolved problem. I've measured the voltage at the VNT governor plug and it's consistently 8.4V. Vida says the voltage should be between 0V and battery voltage..... which 8.4V is! I've decided to replace the VNT governor with a new Pierburg unit £60 online as opposed to £195 for the Volvo part. However..... I still have the same symptoms. Does anyone have a reference voltage for the VNT governor supply? Is 8.4V normal? I've also suspected a faulty relay but looking through the manuals and VIDA I can't find a reference to a relay for the turbo governor. Any ideas??