2002 Volvo S40, 4-cyl. Non-Turbo, approx. 68K miles. Auto trans.

Problem: Check Engine light comes on. I read the OBDII generic code with an Actron Scanner and it shows a P0015 code. The scanner indicates a camshaft timing issue. It doesn’t make any sense to me , as the apparent trigger for this fault is the defroster! If I turn the defroster on or off when the car is being driven, there is no indication of anything wrong. The defroster seems to work OK and there’s no change (that I can determine) in drivability. However, at the next restart of the engine, the Check Engine light comes on. I've noticed also that this seems to happen when the defroster is used in conjunction with the heater. During the summer months, I've used the defroster with the A/C and have had no issues. As the weather has become cooler, the first time I've used the defroster with heat, the CEL comes on! I’ve reset the light a few times but the CEL comes on virtually every time after the defroster is used, and the same code appears. If I don’t use the defroster, the CEL remains off until the next time I use it. I was able to obtain an explanation of sorts for the P0015 code, although this too didn’t seem to correlate with the defroster use. Here’s what I received:

P0015 is indeed an SAE defined OBD II diagnostic trouble code. In fact, P0015 cross references to the Volvo proprietary code ECM-61. Below is information pertaining to this DTC, specifically for your vehicle?
P0015/ECM-61: VARIABLE VALVE TIMING CONTROL VALVE

Fault Conditions

Each time that the engine is switched off, the camshaft pulley sets itself in the locked position. The ECM checks that the camshaft pulley leaves the locked position when the engine is started again. DTC ECM-61 is stored if the ECM detects that the camshaft pulley is in the locked position.

Possible Causes:

Low oil pressure in the engine
Blocked oil ducts for the VVT control valve
Defective VVT control valve

I've had the car to the local Volvo dealer for this problem and they didn't have a clue as to what the problem was. They "read" an OBDII/Volvo code that indicated a bad thermostat (which did not show up on my reader) and replaced it. The also said they checked the oil pressure and it was OK. My explanation for the defroster CEL issue was "A lot of Volvos have this problem and it's no concern". Now I don't buy that and they certainly won't get any more of my business unless absolutely necessary. I'm kind of stuck here because the next closest Volvo dealer is 75 miles away if I wanted another opinion. I'm a pretty fair backyard mechanic so I do most routine (and not-so-routine) work myself. I've changed out the CVVT solenoid valve to no avail. Could there be sludge or something like that built up in the VVT control valve on the CAMs? It's been recommended to add a quart of ATF to the oil, run the car at idle for about 15 min. and drain and refill the oil with new. ATF is supposed (I'm told) to be very good at cleaning out sludge and deposits. Any experience with that?

If the problem really is the VVT control valve, I’d like to know what the defroster/heater connection is. I hope someone can make some sense of this….

Thanks in advance to anyone that can help.