2.4i Camshaft reset solenoid valve.

[pinballdave]

I have a C70 2.4i (B5244S4) that's got the MIL lit due to an ECM-640F "Camshaft position, inlet - Signal too High" fault code. The VIDA description states that this fault code is set if the camshaft adaptation value is higher than it should be (27CA +/-8)

Viewing the camshaft adaptation value on VIDA shows it stuck at 40.00CA, and the live readings 'ECM-Camshaft shifting angle, inlet' and 'ECM-Camshaft advance angle, inlet nominal' are both stuck at 0 CA. So it appears that I'm getting no camshaft adjustment at all.

I've done an oil and filter change, checked the timing marks on the cam belt pulleys, and pulled and cleaned out the reset solenoid, but the fault remains.

I've checked the drive voltage to the solenoid on a scope, and it's a good square-wave signal that varies it's mark/space ratio as you rev the engine.

When tested on the bench, the solenoid also 'clicks' when you apply 12v to the connector, but I'm unsure if the valve part is working correctly.

Could the solenoid still be faulty, and are there any more tests I can perform to try to diagnose it? Or is it worth just swapping it out as a final check before spending the big bucks on a replacement VVT pulley, and the cam locking tools needed to change it out?

[cheshired5]

It would appear to be leaning towards a faulty reset valve.

Have you checked the resistance on the unplugged valve between the two pins?
It should be 3-5ohms

[pinballdave]

Originally Posted by cheshired5

Have you checked the resistance on the unplugged valve between the two pins?

I haven't, but it operated on the bench PSU without tripping the over-current (2A), so I'm fairly confident the solenoid coil is not open-circuit or short-circuit. You could feel the movement of the solenoid operating from the bench PSU when it was held, but whether the valve part is working or not is unknown.

[cheshired5]

It's a very specific resistance range so it not being short or open doesn't really confirm anything.

Best to test it and my guess is that it will be out of range.

[pinballdave]

Coil resistance is 4 ohms exactly, so I don't think the solenoid part of the camshaft reset valve is the problem.

I'm more interested in knowing if there are any tests to check the hydraulic valve part, which way oil should flow through the valve, whether flow should be cut off when energised or not etc.

[cheshired5]

I don't know off hand but I do know that in Vida there are a finite number of reasons for the "signal too high" code so of all of the reasons available, which one(s) are definitely eliminated and which are now left?

I'm also assuming you've reset the ECM adaptions as per Vida procedure.

You may also get further component information in the technical sections of Information in Vida.

[pinballdave]

I have done the reset ECM adaptations procedure, and then gone for a long drive to allow it to relearn, but it hasn't helped and the same fault code returns.

From VIDA the possible sources of the 'Signal too high' error are listed as...

Poor quality engine oil.
The timing gear belt has jumped off the cogs.
Incorrectly adjusted camshafts.
Damaged reset valve.
Mechanical fault in the variable valve timing (VVT) unit.

So I've done the oil change, I've checked the cam timing marks, now I'm onto the reset valve.

After that it's checking that the cam pulleys are 'correctly adjusted'. I can't rule this out, as I bought the car with the fault present, so it's possible that someone has played around with cam timing in the past. But this needs the camshaft locking tools, which I don't yet have (despite running 5 cylinder Volvos for almost 20 years!).

If that doesn't do it, then all that's left is the VVT pulley.

[cheshired5]

Originally Posted by pinballdave

I bought the car with the fault present, so it's possible that someone has played around with cam timing in the past.

It would have been helpful to know this ^^^^^ right from the beginning.

The chances of a car being sold with a known fault that's any easy fix with a code reset are slim to none.
I'd be buying some tools and reading up on the cam locking procedure.

[pinballdave]

Originally Posted by cheshired5

It would have been helpful to know this ^^^^^ right from the beginning.

Yeah, I probably should have mentioned it in the first post, but at that stage I was just working through the problem logically and wanting to know if anyone knew of any tests that could rule out the solenoid valve.

You are of course correct in your assumptions, and I thank you for sharing your wisdom. I've just changed the valve and the fault remains, so it will be on to buying the tools and checking the pulleys and cam timing...

I was hoping that it would be a simple fault the previous owner or their garage had failed to diagnose correctly. The car came with a huge shopping list of faults (that allowed me to buy the car for about half the normal price), and so far it's cost me less than £50 and a long weekend with the spanners out, to cross off everything from the list apart from this VVT problem.

[cheshired5]

At least it was cheap and you'll hopefully still have a well running bargain albeit for a a little more cost and hassle.

Good luck with the outcome.