[lustek]

Hi everyone,

I'm working on a BMW E46 with the M54B30 engine (Double VANOS, single housing). I've been diagnosing this for a few days and I'm stuck – hoping someone with hands-on experience can point me in the right direction.

The problem:
Both VANOS units are completely inactive. Values in INPA are frozen – intake shows approximately +206° and exhaust approximately −105° – and neither changes at any RPM, including when blipping the throttle. The only fault code stored is the exhaust camshaft position sensor (CMP).

What I've already done and checked:

• Exhaust CMP sensor – replaced with a known-good unit, fault returns immediately on startup
  
• Wiring harness to both solenoids and to both CMP sensors – fully checked, no breaks or shorts
  
• Solenoid self-test – when solenoid connectors are unplugged, open-load faults appear instantly, which suggests the solenoids and their drivers are functional
  
• Direct 12V battery test on one solenoid – plunger extends, solenoid is mechanically OK
  
• PWM signal check – connected a 12V test bulb (as a load) to the solenoid connector with the engine running. Bulb lights up immediately and stays at constant brightness regardless of throttle input. No flicker, no dimming. This tells me DME is outputting a steady DC voltage instead of a PWM signal – consistent with it having lost CMP feedback and going into a fallback/limp state
  
• Full VANOS disassembly – all O-rings and seals replaced, piston clearances corrected (there was significant play before the rebuild)
  
• Post-rebuild retest – no change. VANOS still frozen at the same values, same CMP exhaust fault
  

My questions:

1. Could the oil supply to the VANOS unit be the root cause? E.g. blocked oil gallery, faulty oil pressure control valve on the front of the engine, or low oil pressure overall? Could insufficient oil pressure prevent the mechanism from moving enough for the CMP signal to be valid?
   
2. Is there a way to verify VANOS oil supply pressure without specialist equipment?
   
3. Has anyone seen a case where the DME itself caused this – stuck in fallback, refusing to output PWM even with everything else correct?
   
4. Any other checks you would do before condemning the DME or pulling the front of the engine again?
   

Any help or experience with this specific failure pattern would be greatly appreciated.

Thank you.