High purge solenoid voltage spike

Hi,i have a question,i have checked a Audi TT purge solenoid valve on off waveform with scope,the trouble code keep on popping the PURGE SOLENOID CONTROL,activation
PURGE SOLENOID CONTROL,electrical
These 2 codes
But the ECU Is controlling the purge i can see it from the scope with clear squarewave 12v - 0v
The solenoid is clicking as well
But what i noticed is it creates a very high voltage spike which over 50v, is that normal for this type of solenoid?
Will try to capture the waveform and post it here

Evanlip wrote: Hi,i have a question,i have checked a Audi TT purge solenoid valve on off waveform with scope,the trouble code keep on popping the PURGE SOLENOID CONTROL,activation
PURGE SOLENOID CONTROL,electrical
These 2 codes
But the ECU Is controlling the purge i can see it from the scope with clear squarewave 12v - 0v
The solenoid is clicking as well
But what i noticed is it creates a very high voltage spike which over 50v, is that normal for this type of solenoid?
Will try to capture the waveform and post it here

Voltage spikes are ok. 50v is not that much of a spike.

hi,guys,looks like the purge solenoid and computer are not the issue here,so i tried to change the charcoal canister.



when i removed the canister i can hear the sound of the canister when i shake it,it sounds like the hand shaker musical instrument.


i ordered a genuine brand new and i did the same way,it doesn't sound like the old one.
so this give me a bit more confidence to put it into the car.
i brought it for few test drive,so far so good.no trouble codes so far.
but can someone explain this,why the computer trigger these 2 codes "IF" canister was really the cause?
thanks guys

What DTC exactly did you get?

i am so sorry,i didn't note down the P code, my bad.
what i do remember the description are
PURGE SOLENOID CONTROL,activation
PURGE SOLENOID CONTROL,electrical
2 codes at the same time.
now the codes are gone.
so sorry bro
otherwise i will try to install the old canister and recheck again.

Codes description doesn't look like it was set by a faulty charcoal canister. :dry:

Ya man,thats what i was thinking,i checked the solenoid circuit with scope,everything is good,clear 12V 0V squarewave.
Made me no choice to look for other possibilities.
What do u think?

Was it a hard fault with the old canister? Did you get CEL immediately after clearing the codes? If it was intermittent maybe a solenoid itself becomes faulty when heating in engine bay or some wiring issues.

The CEL didnt come out after i clearing it.
THe code will only come out after a few kilometers drive.
I will keep test driving the ca first,before i can call it a fixed

Wonder what the code set criteria for this code is. :huh: Anyway, good move by scoping the purge before replacing it!

I've never worked on a TT, but I have seen other makes/models set purge codes due to EVAP leaks or faulty pressure sensors. In those cases, the PCM was commanding canister purge, and wasn't seeing a corresponding change in fuel tank pressure. It's silly fault detection logic, but that's how some are

Ya man,this is why we need the scope.
Thanks Tyler,im not sure about this too,hope i can give this car a fix.
Anyway your explanation is good and make sense.
Thanks

I had a 2012 Versa with P0444 which had come to shop. It had the Purge Control Solenoid replaced by another shop for the same (only) dtc. The problem I found was erratic voltage signal sent to ecm by evaporative control pressure sensor. There was no pressure sensor code set. Go figure... :silly: