My vanos is stuck on

[matt]

There is no PWM in the M50TU. It's on or off. Same with the MS41 based M52. The MS42 and above have real PWM cam control.

[JGood]

Back to the drawing board...

Why can't I get a correct reading on a multimeter then? If it's 12v on, or 12v off, I should see that....

[nando]

matt, do you know anything about the operation of the EVAP valve?

PWM can still be on off, but it was really just a guess based on the wiring diagrams.

[matt]

The evap valve is PWMed. The duty cycle depends on how much extra fuel vapor the engine can handle at a given moment. IE at high throttle, it will be more open because there will be more air flow to absorb the vapor and keep the motor running smoothly.

Don't worry too much about the voltage you see on the VANOS line. The nature of a MOSFET solid-state low-side driver is that it may leak voltage, but it won't drive significant current through its load (the VANOS) without the proper signal. Thats why you got the correct result with a load (LED) but an incorrect result without a load (DMM in voltage mode).

[nando]

okay, that helps - thanks. making a PWM based EVAP map from scratch isn't easy when you don't know when it's supposed to open. :p

[JGood]

Don't worry too much about the voltage you see on the VANOS line. The nature of a MOSFET solid-state low-side driver is that it may leak voltage, but it won't drive significant current through its load (the VANOS) without the proper signal. Thats why you got the correct result with a load (LED) but an incorrect result without a load (DMM in voltage mode).

Thank you!

[hoveringuy]

The evap valve is PWMed. The duty cycle depends on how much extra fuel vapor the engine can handle at a given moment. IE at high throttle, it will be more open because there will be more air flow to absorb the vapor and keep the motor running smoothly.

Don't worry too much about the voltage you see on the VANOS line. The nature of a MOSFET solid-state low-side driver is that it may leak voltage, but it won't drive significant current through its load (the VANOS) without the proper signal. Thats why you got the correct result with a load (LED) but an incorrect result without a load (DMM in voltage mode).

Spoken like a geek. The MOSFET can look like a closed circuit at the milliamp levels of current used by the multimeter but for any significant amount of current (like driving the solenoid) it will be open.

The LED draws enough current to tell you what's really happening.

[matt]

I will take that as a compliment. Thank you, sir.