Wiring diagram needed for Fabia Mk1 VRS 1.9tdi 130 ideally.

Specifically ECU pinouts and wiring to N75 valve please.

Any suggestions or help please?

Why is it acting up ?

One end of the N75 (pin T6z/5) goes direct to the ECU (pin T81a/62) - Lilac/White.

The other end (pin T6z/3) is connected to the sensor positive supply via Fuse 24 which is fed from the ECU power relay

Bump, so Im getting an intermittent ground/open signal on the n75 (says so by vagcom and I can see my boost flicking from on boost to 0 every so often), I assume its the wiring at fault.

Where is this power relay from the ecu? Is there a common breakage along this line?

Thanks in advance!

Bump, so Im getting an intermittent ground/open signal on the n75 (says so by vagcom and I can see my boost flicking from on boost to 0 every so often), I assume its the wiring at fault.

Where is this power relay from the ecu? Is there a common breakage along this line?

Thanks in advance!

Manuals here

http://sziget.mine.nu/~tAB/nem_megnezni/Skoda/Biblia/Fabia/

The wiring often breaks on the N75 itself as the loom is quite tight and gets pulled on, especially when fitting a cambelt or strut brace for example.

Thanks for the manual!

The wiring often breaks on the N75 itself as the loom is quite tight and gets pulled on, especially when fitting a cambelt or strut brace for example.

aha.. Yes I have been messing around with the strut brace a few times, guessing I should remove the plug and have a play with that first then. Thanks!

Update to come..

I can see boost dropping to 0 spontaneously, the VAGCOM says the N75 valve intermittant shorting or open circuit, my other diagnostic gadget says im losing power to the wastegate solenoid (im guessing this also means the n75 valve)

I disconnected the plug from the vacuum box and tested the connections -

pin 3 - blue black, 11.95v (consistent), power live?

pin 5 - purple white, 0.10v (consistent), signal wire?

pin 6 - brown white, 0v (ground?)

pin 4 - blue black, 11.95v (consistent), power live?

Non of them are fluctuating so I assume wiring is fine.

RE the purple (lilac) wire - would this fire up at start of turn 2 of ignition? Im guessing this is how the ECU can detect if the solenoid is working or not.

Ok so I had a few more searching and I found that this possibly be my problem.

http://briskoda.net/forums/topic/91156-today-i-finally-fixed-my-fabia/

Suppose this leaves the box is at fault? :( I keep read threads that its a rock solid unit and it does not go wrong.... hmmm..

Also on a side note, how does one signal wire control EGR, solenoid for the turbo and brake servo???

Any additional input would be great (even a confirmation), im just sitting here looking for a new vac box and contemplating can I be bothered to change the FARB bushes...

Also on a side note, how does one signal wire control EGR, solenoid for the turbo and brake servo???

All very black magic isn't it. Varies between ASZ and BLT engines, as on the BLT intake changover flap is separate from EGR and electrically controlled with a stepper motor.

Anyway, the brake servo is directly connected to the tandem pump via a non return valve. So the vacuum box controls air intake changeover flap, EGR and turbo. It does this by the ECU applying a modulated voltage for each function. Vacuum is then distributed within the vacuum box by modulator solenoid valves, that only respond to certain modulated voltages.

see post #3.

There is no ground involved. The lilac/white wire is pulled down to ground inside the ECU to switch on the solenoid.

How did you measure the voltage at pin 5?

You should measure the voltage against battery ground with the solenoid still connected

The solenoid is off when you read 12v and on when it is close to zero.

What is the resistance between pins 3 and 5 with the plug disconnected?

All very black magic isn't it. Varies between ASZ and BLT engines, as on the BLT intake changover flap is separate from EGR and electrically controlled with a stepper motor.

Anyway, the brake servo is directly connected to the tandem pump via a non return valve. So the vacuum box controls air intake changeover flap, EGR and turbo. It does this by the ECU applying a modulated voltage for each function. Vacuum is then distributed within the vacuum box by modulator solenoid valves, that only respond to certain modulated voltages.

Edit: Kool, still learning, interesting though

see post #3.

There is no ground involved. The lilac/white wire is pulled down to ground inside the ECU to switch on the solenoid.

How did you measure the voltage at pin 5?

You should measure the voltage against battery ground with the solenoid still connected

The solenoid is off when you read 12v and on when it is close to zero.

What is the resistance between pins 3 and 5 with the plug disconnected?

Sorry, I didnt realise what p6z/3 meant.

I unplugged pin 5 and measured voltage at off position (0.10v) and ignition position 2 (~2.30v), how else can you measure the voltage without removing plug? splice the wire?

Pin 5 resistance is between 8-12ohms from battery -ve. - When switched to ignition position 2 it starts at ~60ohms and drops 1ohm every 0.5 seconds? saw it keep going down till about 45 and I got bored and stopped reading it, I assume it keeps dropping to 0 ohms?

Pin 3, dont think I can get a reading.. - When switched to ignition position 2 it still has no reading.

Edit 2: Sorry I may have misread the question there.. you meant stick one probe at pin 3 and one at pin 5? This wouldn't give me a reading. I thought pin 3 is send and pin 5 is receive, unless it was connected with a load it would not give me a number?

Sorry, I didnt realise what p6z/3 meant.

I unplugged pin 5 and measured voltage at off position (0.10v) and ignition position 2 (~2.30v), how else can you measure the voltage without removing plug? splice the wire?

Pin 5 resistance is between 8-12ohms from battery -ve. - When switched to ignition position 2 it starts at ~60ohms and drops 1ohm every 0.5 seconds? saw it keep going down till about 45 and I got bored and stopped reading it, I assume it keeps dropping to 0 ohms?

Pin 3, dont think I can get a reading.. - When switched to ignition position 2 it still has no reading.

Edit 2: Sorry I may have misread the question there.. you meant stick one probe at pin 3 and one at pin 5? This wouldn't give me a reading. I thought pin 3 is send and pin 5 is receive, unless it was connected with a load it would not give me a number?

You would have to use a piercing probe or a breakout connector. Without the solenoid in circuit the reading is meaningless. You could use a sharp thin sewing needle to pierce the insulation and take the other end of your meter to battery -ve. Meter on volts.

For the resistance measurement, disconnect the plug and put the meter probes on pins 3 and 5. Meter on resistance will give you the resistance of the solenoid.

If you are having a hard time figuring out what is going on, then think of it like this...

With you meter on volts, connect the +ve probe to battery +ve. If you connect the -ve probe to battery -ve you get 12V on the meter. If you disconnect the -ve probe you get nothing. All the ECU is doing is connecting and disconnecting the -ve.

HTH

You would have to use a piercing probe or a breakout connector. Without the solenoid in circuit the reading is meaningless. You could use a sharp thin sewing needle to pierce the insulation and take the other end of your meter to battery -ve. Meter on volts.

For the resistance measurement, disconnect the plug and put the meter probes on pins 3 and 5. Meter on resistance will give you the resistance of the solenoid.

If you are having a hard time figuring out what is going on, then think of it like this...

With you meter on volts, connect the +ve probe to battery +ve. If you connect the -ve probe to battery -ve you get 12V on the meter. If you disconnect the -ve probe you get nothing. All the ECU is doing is connecting and disconnecting the -ve.

HTH

Blond moment! Sorry! I was referring to the plug all along (I assumed there was a wire breakage and thought you was asking me to test the wiring) not the actual vacuum unit.

OK so now pin 3 and pin 5 of the vacuum unit is ~16.7 ohms, which is the resistance of the solenoid. Phew.. got there in the end, is 16.7 ohms good?

Further update, I tried to do the boost pressure test with vagcom (switches the N75 valve on and off a few times @ 1.5k rpm). works ok for the first few goes, then it just stops working.

Found out that its the vacuum unit.. :(

Does anyone know where to get one of these? Dealers wanting 140 plus vat....... p/n is

6Q0 906 625 C

Found out that its the vacuum unit.. :(

Does anyone know where to get one of these? Dealers wanting 140 plus vat....... p/n is

6Q0 906 625 C

Make sure you get the 'C' version. VW and Audi offer a 'G' version as a replacement for the same engine as yours, but on SOME Fabias it works unreliably. Such is the wonderful world of VAG :(

Make sure you get the 'C' version. VW and Audi offer a 'G' version as a replacement for the same engine as yours, but on SOME Fabias it works unreliably. Such is the wonderful world of VAG :(

Hindsight it a lovely thing isnt it, I bought the one ending with A and plugged it in. Found it didnt work but it cured my intermittent ground/open problem so I knew it was the module not working NOT the wiring. Unfortunately, this type didn't work for the VRS. Trying to find some breakers on ebay atm to see if they got any..