BKP Underboost Issues!

[Crasher]

At idle the N75 is open to pull the turbo back to minimum boost and it starts to cycle, venting off the vacuum, to alter the rods position as required. In Basic settings there is a test to operate the N75 at dle where you will see it change position every 10 seconds or so and the boost displayed will change from approx. 995 mBar to approx. 1200 mBar and back plus you should hear the turbo spool up, if the function is not in the menu it is block 011.

[Chris01243]

At idle the N75 is open to pull the turbo back to minimum boost and it starts to cycle, venting off the vacuum, to alter the rods position as required. In Basic settings there is a test to operate the N75 at dle where you will see it change position every 10 seconds or so and the boost displayed will change from approx. 995 mBar to approx. 1200 mBar and back plus you should hear the turbo spool up, if the function is not in the menu it is block 011.

Thanks for explaining this. I’m trying to source a scanner that will do basic settings / functions. All actuator tests I can do are for fans and glow plugs etc.

I have checked I have a feed to the n75 and EGR cooler solenoid too. With a test light, I have power to both. When I put my test light on positive, so I can check the earths, on the N75 with the engine running I have a very dim earth. On the EGR side I don’t have anything.

Taken the scuttle panel off and found the ECU is incredibly corroded. Will try and take the metal lock off tomorrow so I can check the pins. Have you come across this before?

[Crasher]

Some Passat 3C and later type 36 ECU’s I have seen with heavy corrosion damage when in a few cases has got inside the ECU causing strange random faults.

[mickeybo]

After reading the above reply then where does the turbo pressure solenoid (position sensor) need a answer

[Chris01243]

Some Passat 3C and later type 36 ECU’s I have seen with heavy corrosion damage when in a few cases has got inside the ECU causing strange random faults.

I have a diesel SIMOS PPD1.5 ECU.
Removed it today to check for corrosion in the plugs and continuity to the EGR and N75 solenoids.

No corrosion found, however the casing on the ECU is very rough. Very oxidised from water damage. I’m a bit apprehensive to send this away to be tested as I would of thought I would have other faults occur also?

Since connecting the ECU back up, I have my ground for the N18 back. Whether or not this be a coincidence or I had something wrong before.

Sadly the car still drives the same and chucking plenty of blue smoke out. Puffed a load out on a gear change today which I hadn’t noticed previously.

[mickeybo]

have you not checked out ecu earth for turbo pressure control solenoid at b29 & exhaust gas cooler solenoid at bt29. The very most likely cause of your problem not boosting

[Chris01243]

have you not checked out ecu earth for turbo pressure control solenoid at b29 & exhaust gas cooler solenoid at bt29. The very most likely cause of your problem not boosting

That’s what I done today. Pin 15 and Pin 29 on the right hand ECU plug goes to the N75 and N18 solenoids, both have good continuity. I disconnected the plug from the ECU and the solenoids, put 12v down the wire and measured the voltage out with a multi metre and getting the full amount so I know those wires are good.

I have no way of testing the ECU itself without sending it off to BBA Reman / ECU Testing but it doesn’t look great.

Sadly money is an issue when it comes down to this car now as I’ve spent an absolute fortune on it recently.. it’s one of those situations where you don’t know when to call it a day. Fortunately I have another car I can use in the mean time.