Hi all,

Recently picked up a 2004 Continental GT. Managed to resolve most of the VCDS codes (new battery, new seat control module, etc.) However, there are four turbo related codes which I have listed below that keep coming back after clearing and driving for a few minutes. These are the last codes to get this car error free...

Idle is super smooth at 520rpm. No check engine light. Drives fine and feels quick but measured acceleration using VCDS today and it's coming back as 0-60mph 6.2 seconds so definitely underpowered. Boost pressure (specified) stuck on 1000mbar and N75 always on 0.00%. Boost pressure (actual) reaches ~1300mbar on a WOT run on left and right turbo.

Engine I
18995 - Turbocharger Boost Control Position Sensor Circuit
P2563 - 008 - Implausible Signal

18693 - Boost Pressure Control Valve (N249)
P2261 - 008 - Mechanical Malfunction - Intermittent

Engine II
17867 - Exhaust Gas Temp Sensor 2 (G236)
P1459 - 008 - Implausible Signal

19019 - Turbocharger Boost Control Position Sensor 2
P2587 - 008 - Implausible Signal

19540 - Turbo/Super Charger Bypass Valve; Bank 2
P3084 - 008 - Mechanical Malfunction - Intermittent

The exhaust gas temp sensor 2 error code has only occurred once today after my WOT run. The other 4 codes are the reoccurring ones.

Not sure where to start. I know turbos are controlled by vacuum. Should I start with a smoke test or is it unlikely as idle is smooth and can't hear vacuum pump running when I press brake which is classic sign of leak on this car? Anything else I can check using VCDS before I start tearing engine apart to replace control valves and position sensors? (I'm aware some of these can only be accessed with engine removed)

Would appreciate hearing from anyone who has had these codes before and common culprits to look for. Thank you so much.

 

To be clear the turbos only use boost to activate the wastegate off the n75 boost control solenoids...Bentley calls these solenoids by a different number, don't recall. Any way there is one above the alternator and the other is buried by the left turbo.

Now N249 is the turbo bypass solenoid. This item uses vacuum to purge the turbo of pressure when the throttle body is closed...de- acceleration.

So N249 is possibly bad (not likely..but?) . The wiring, vacuum leak or a kinked vacume line to the turbo bypass diaphragm, regarding N249.

Fix or replace the malfunctioning ETS G236. There are numerous procedures on this forum about PCB board replacereplacement or re-flowing the solder. Just do a online query.


Your boost of Mbar 1300 seems high...18psi.

A smoke test is a good start and might lead us to a legitimate recomendation.

Best

E

 

Hi E,

Thanks, that's a lot of useful information. I will start with a smoke test and go from there.

For the 1300mbar reading, I believe this includes 1000mbar absolute pressure which is shown when the car is just idling and not producing boost. Therefore, you could say it is producing 300mbar boost, which is 4.35psi. I read somewhere that this car should be producing around 700mbar boost.

Thanks,
H

 

~Update~

I finally had time to take some actions towards addressing the boost issue on this car. I managed to smoke test the car and identified leaks in the bulkhead lines, as well as the turbo solenoids mounted above the gearbox. Normally such a diagnosis would have this car sentenced to have its' engine pulled, but I was determined to find a workaround, learn a thing or two along the way, whilst hopefully trying to improve the design for future accessibility.

For the bulkhead bypass, all credit goes to @Stevieshutts as I followed his method.

For the boost solenoids, I bought four used solenoids (two grey dump valve solenoids and two black wastegate actuator solenoids) for a whopping £25 off ebay. Coupled with some plug connectors, 2-core automotive wiring, wiring diagrams from IETIS, heat shields, T-pieces, reinforced silicone hoses and clips. I managed to reposition my solenoids so they sit just behind the NS headlight. Bank 1 dump valve and wastegate actuator were easy to get to, bank 2 was a little tricky as it required cutting a metal pipe but certainly easier than removing the engine. I'll try to do a write up at some point.

The result?

All error codes in Engine I and Engine II cleared and have remained cleared since doing the two bypasses. Smoke tested with no leaks. The engine feels a lot more responsive but I haven't done a new 0-60mph for comparison yet.

However, boost pressure (specified) still remains stuck at 1000mbar and N75 0.00% despite there being no fault codes. Scratching my head on what could be the cause now that I have no fault codes or vacuum leaks to chase. I've done some troubleshooting using VCDS and have shared my observations below in the hope that someone with more experience might be able to point me in the right direction so I'm not chasing any red herrings.

1. Group 063 - Kickdown alignment status says "ERROR", but no stored fault codes. I found that the kickdown switch was rotated slightly anti-clockwise and after rotating it clock-wise, the feel of the click has changed and VCDS now recognises when the kickdown switch is being depressed. After fixing that, I tried to do the alignment in basic settings but nothing happens, so it still says "ERROR".
2. In "Readiness" the only item not ready is the Secondary Air Injection. I don't have any fault codes for this but I do notice that the only time I ever hear the vacuum pump running now is the first 3-5 seconds of a cold start when I can also hear the SAI pump working. Is this normal? Perhaps this indicates a vacuum leak downstream of the SAI solenoids, but I would have thought it would throw a fault code? Also, even if such a leak is depleting the vacuum being supplied to boost solenoids, then surely I should expect my original boost related fault codes to remain?
3. Could N75 or N272 be faulty without throwing any fault codes? Maybe I need to do an adaptation? I done output tests and can hear clicking.
4.VCDS observations when looking at charge pressure related measuring blocks:
Group 111 - all four charge pressure control adaptations show 0.0%
Group 114 - boost pressure control (N75) 0.0%
Group 115 - boost specified stuck at 990-1000mbar, but boost actual rises to about 1200-1300mbar at WOT
Group 116 - Correction factor for fuel, coolant temp and air intake tempt is -50.0%
Group 119 - Boost Pressure Control Adapt 0.0%

 

Hello,

Nice work and great that you relocated the turbo bypass solenoids.

The N75 solenoids are.not part of the "above transmission" units. N75(s) reside ... One of the solenoids is on the right, bank (1) above the alternator and the other N75 is on the left bank (2) buried near the left turbo.

The right side N 75 can be serviced by removing the front bumper and associated bits. The left N75 is engine out.

Anyway they may be or hopefully not the issue. Also N75 is not a vacuum activated solenoid. They receive boost pressure and open the wastegate at the appropriate pressure point determined by the ECU mapping.

 

Hi E,

Thanks for this input. Yes, N75 (right side) and N272 (left side) are not easy to reach. If I understand correctly, there are 3 nozzles to these solenoids:

1- Wastegate actuator
2- Boost pressure source
3- Vent to intake pipe

As N75 uses boost pressure to open the wastegate, if there was a leak to the (1) actuator or (2) boost pressure source, I would expect the car to be in overboost condition instead of no boost. Even if N75 solenoid was faulty and stuck on 0.00%, I would still expect there to be a fault code or to see the ECU requesting boost but just unable to build boost due to wastegate being kept open by faulty N75.

What I'm trying to say is, I believe N75 being 0.00% is the symptom and not the cause. I feel like because the ECU is in a state whereby it is not requesting boost, it is commanding N75 to stay 0.00% and keep wastegate open.

I am wondering whether this is due to the previous fault of vacuum leak to wastegate actuator, and although fault codes have been cleared, the "limp" mode has remained latched and needs to undergo some sort of adaptation reset so that the ECU feels comfortable to start requesting boost again? According to some VCDS forum links, I know some VAG cars have this procedure but can't see anything specifically for this car.

If anyone has 2004-2006 Continental GT and VCDS, it would be great to know what readings they normally get for Boost Pressure (specified), (Boost Pressure (actual) and N75 duty cycle?

 

Yes a fault in the piping of N75 could throw an overboost DTC and interject limp mode until the next drive cycle. Try the VCDS output test option for the engine control modules for both banks. Might reveal something.

There is a chance the turbo/turbos aren't spinning..mechanical issues?

Contimplate pulling the air box and aluminum cone. With an inspection camera view the turbo vains, see if the impeller moves easily. Also pull the lower intercooler rubber boots and see if there are aluminum flakes. A bit of oil will drop out as per normal.

 

The vanes look good and definitely spin freely as both banks are making 1200-1300mbar (boost actual) under WOT. This suggests turbos are capable of making boost but cannot make more than this while ECU not requesting boost (1000mbar boost specified) as wastegate is commanded to stay open.

Got under the car and ran output tests. I can hear the DV open/close and can see the wastegate rods move freely when commanding the vacuum solenoids on both banks. However, I did notice that I can only get rods to move about 2-3 times before the car runs out of stored vacuum and I need to restart the engine and let it run for a few seconds to repeat the test, but I guess this could be normal as the vacuum reservoir is designed to be topped up with engine or pump running.

Unfortunately can't test whether the positive pressure N75 solenoid moves the rod using output tests as obviously there's no positive pressure when the engine is off, but as we previously established, the solenoids click on both banks and there are no fault codes.

I did manage to get the car to request boost and command N75 on two occasions:
1. Disconnected the battery and reconnected it. Started the car and blipped the throttle and it worked once.
2. Went for a 20 minute drive, there was no boost requested or N75 activity the whole journey, but when I got home, I blipped the throttle and it worked once.
Since then, I haven't been able to replicate even under similar conditions.

Just seems strange to me that the ECU can decide not to request boost but not leave any record or fault of why it made that decision? Do you think if I put it on ODIS I can possibly learn something that VCDS doesn't tell? ECU problem? Hard reset of adaptations needed? Honestly running out of ideas as everything seems good mechanically and according to VCDS measuring blocks.

Sods law that I find a solution for the turbo solenoids above the gearbox without removing the engine, and I'm faced with a mysterious unsolvable problem

I don't think the problem is N75 solenoids, as other threads indicate you should either have a fault code, they won't click on output test, or the car still requests boost but there is no N75 activity. My situation is different as the ECU is actively deciding to not request boost and command wastegate open.

Appreciate any ideas on what to check next, thank you!

 

So..long shot possibly. The small black solenoids above the transmission can fail in the open position. That would cause a plausible explanation as to no boost, since they vent to the atmosphere. One of the small vacume lines under the rear B cover is the vacume supply line to the above transmission solenoids, all 4. Disconnect that small line and plug the vacuum side and re-test. This will bypass the turbo dump valve control n249 function. Some VW & Audi followers believe this improves turbo boost spool up.

I did this bypass before replaceing the pipes with metal. I don’t remember which line got pluged. Anyway the car boosted and the lines got replaced.

 

This car had vacuum leak at the gearbox solenoids location. To reposition my 2 black wastegate and 2 grey dump valve solenoids to NS headlight area without removing the engine, I had to source spare ones on eBay and plumb the vacuum and wire the electrical connections appropriately. I tested all four solenoids before installation and confirmed they work as intended when energised and not energised. I suppose this is confirmed by the fact that everything works as intended now in output tests and I no longer have the boost position sensor and N249/bypass valve fault codes anymore.

Ah yes, the N249 delete mod. I wasn't sure if anyone here was also familiar with it. I actually did a similar thing on this car initially as I also read a lot of 1.8T owners did the same and it would make my installation less cluttered as I would only need to install the 2 black solenoids properly, as the dump valve would be setup to operate directly on the manifold vacuum. It worked and there was no fault codes but as I still had the existing problem of no boost specified, I decided to go through the trouble of including the grey dump valve solenoids to make it like original just in case this ECU was more sensitive than the 1.8T but alas it made no difference.

Thanks for the idea but have already tried that and confirmed the 4 turbo solenoids (originally positioned above gearbox) are working properly.

 

Just reporting back to say this has now been resolved. My vacuum bypass on a 2004 model without removing the engine was a success and I now have boost and no fault codes

For those interested:
After doing my bypass, I still had no boost being requested by ECU despite no fault codes. I would get boost specified and N75 duty cycle briefly after disconnecting and reconnecting battery then stops again. I watched all the data on VCDS carefully and could see Oxygen Sensor Bank 1 sometimes drops to -20% every couple of minutes for a split second before recovering. Fuel trims were good. Investigated further and found bank 1 secondary air combi valve appeared to be stuck open, so I replaced it (probably why that readiness monitor was the only one not going ready).

While putting it back together, I checked the 3 ignition coils that are accessible on bank 1 without removing manifold (cylinders 4-6) and found cylinder 5 had some oil in ignition coil (most likely spark plug tube seals need doing next time I change spark plugs). Maybe this was causing intermittent misfire and disabling boost, but early ECU software doesn't appear to support misfire monitoring so no fault codes and can't see any misfire monitoring data in VCDS. I also found cylinder 4 spark could be loosened by hand, so I made sure to torque it to spec.

I also read on Audi forums about someone who had similar issue on a 1.8T and managed to get their boost adaptations reset by disconnecting battery then reconnecting then makes sure you drive your car normally going on/off boost. The important bit was to not rev the car in Park/Neutral before doing this as otherwise it would go into a soft limp mode again.

Anyway, I'm not sure which of the 3 things above did it, but it has been 2 weeks since I did the above and car works perfectly and getting 600mbar boost as expected of stock Continental GT. Checked ignition coils again and no oil, so I guess spark plug tube seals can wait until I next do spark plugs in the summer.

Thanks 1eapplebaum for your support. I've enjoyed the process of getting this car sorted and learned a lot - hope others who read also benefit from this and learn something.

 

Thanks for following up. Hopefully others will benefit from our discussions and your diligence.

E

 

@Hamodi - it is amazing you did this without engine out (replacement / reposition) - can you share the procedure with some photos or diagrams as DIY manual?