17956-boost Pressure Regulation Valve N75

[fireblade5437]

Hi

After getting VAG COM up and running and resetting my fault codes for the airbag i have noticed that in Engine '01' address i have the following fault code:
17956 - BOOST PRESSURE REGULATION VALVE (N75) OPEN CIRCUIT.

Does anyone know where the location of this valve is ? and what is it's operation ?

regards

Alan

Passat is a 1999-2000 B5 1.8T SEL

[raceipsa]

I will let more tech savy people explain the N75 (there are various threads on it and photos of its location -- look under the pancake valve on intake hose, has an electrical connection). But my recent experience may help.

The N75 affects boost. I had a broken wire issue with my N75 and no boost. I am GUESSING that the "open circuit" read suggests a broken wire or conenction failure. You can read my woe at the "turbo feels like its missing" post here. My wire failed at the connection to the N75 and a quick re-solder fixed it. I also posted my voltage reads. That is something you can easily check by carefully unplugging the conenction, squishing the rubber protective sleeve away and looking.

Hope this helps.

[raceipsa]

Here is a photo of a N75 on the car:

? on N75 valve

if this does not work, just scroll down some. the thread comes from a current B5 garage forum.

[fireblade5437]

Thanks for the info on the N75 i will be looking at it as soon as poss!

Regards

Alan...

[scotty_passat]

hehe, your car must be pretty slow right now. probably need to buzz out the harness. start by looking right at the connector it might be a visible break...easy to fix.

[pete1]

and what is it's operation ?

It controlls your boost pressure by opening and shutting the wastegate on the turbo. A valve inside the N75 is triggered by an electrical signal from the ECU. When the valve is in one position, boost pressure from the intake manifold is used to mechanically open the wastegate, in the other position vacuum from the intake is used to close the wastegate.

As mentioned already, you likely have a broken wire or just lots of crud in the electrical connection at the N75. Have a look at the connectors and also clean them with "no-residue" electronics cleaner. If you see a broken wire, you can probably solder it by hand.

[fireblade5437]

Hi
thanks to all your replies regarding the N75, 10/10 for all the ones who thought it was a broken wire you were spot on.

Now that i have soldered the wire back on the fault has been cleared by VAG com i have two issues
1. The voltage on the N75 with the engine running should be around 5V and 8V if running?

I have a reading of 0.04V DC not alot of inrush current!
The resistance of the coil is 30.2 Ohms

2. Now i have got the N75 back connected there is a slight rough patch after 5000rpm > 6000rpm now before i repaired the N75 it was smooth at these rpm.
Now all of you have stated that my car would be slow which before was not the case and even when you get by the rough patch i still managed to easily obtain 130MPH (clock reading)

Any thoughts would be appreciated

Alan...

[speedracer329]

hehe, your car must be pretty slow right now. probably need to buzz out the harness. start by looking right at the connector it might be a visible break...easy to fix.

i was swapping in my stock airbox one time, from a CAI, and i got a CEL and my car was sluggish!!, i thought the airbox really restricted it that much, but lol i forgot to reconnect the n75 sensor wire

[raceipsa]

Hi

1. The voltage on the N75 with the engine running should be around 5V and 8V if running?

I have a reading of 0.04V DC not alot of inrush current!
The resistance of the coil is 30.2 Ohms



Alan...

Alan:

My read of voltage was just that - a quick read. I do not know if my voltage is spec, but the N75 works. Again, i read 5 volts at ignition (key turned, motor ready to crank) and about 8 THE OTHER WAY at idle (i.e., an absolute difference of 13 volts). I really do not know what my reads mean, I just wanted a personal baseline in case my fix did not work. Maybe one of the VW-tech subscribers could offer more firm info.

Let us know what you find out.