1.2 TSI EPC Error (P334a)

Jan 30, 2021
9
0
FIX FOR P334A ISSUE…

Having had a couple of 1.2 TSI cars that have demonstrated this fault and investigated further, it seems there’s a design flaw with the turbo actuators on this engine (located just to the right of the exhaust heatshield and mounted on the turbo). The internal position sensor’s plastic slides wear out and this extra slop allows the moving part of the sensor to become jammed at a self-locking angle to the fixed housing. To remedy this:

1. Purchase a 5 lobe security star drive set from Screwfix for about £20 to enable you to undo the 3 anti-tamper screws on the actuator. You'll also need some plastic grease (brake calliper grease will be fine) and spray on lube (must be high temperature & plastic compatible such as silicone or PTFE based - metal lubes may kill the plastics!!).

2. Undo the electrical connector on the actuator by pushing down on the jack whilst gently lifting the tab on the right (fingernails work best if you have them long enough but be careful as these connectors are notorious for becoming brittle and snapping. If this happens you’ll need a small zip tie to hold the connector together when you’re finished). When you see the clip release you can then lift off the jack.

3. Undo the 3 anti-tamper screws (receiving holes circled in picture in picture - two at the top and one slightly hidden at the bottom towards the front of the car) being careful not to drop them.

View attachment 10280

4. Separate the two main halves of the actuator by sliding the black plastic housing to the right. It has runners to keep everything aligned so you'll need to slide it a good distance before it's fully separated but there should be room in the engine bay to do so.

5. Using a small flathead screwdriver, lift the retaining tab up from the top of the position sensor (circled in image) and the moving part of the sensor should now spring away from the housing but still be retained by the spring.

View attachment 10281

6. Use your plastic compatible grease to lubricate the slides on either side of both the moving parts and housing of the sensor being very careful not to stress & deform the spring. Also grease the boss the spring sits on and then re-clip the moving part back into the housing.

7. Use your plastic compatible grease to lubricate the teeth on all the gears on the other half of the actuator (i.e. the sub-assembly remaining mounted on the car). Ask a friend to hold a small mirror and a torch and spray your plastic compatible lube around the metal slide and spring parts to the left of the gears as you won’t be able to get grease on there with it still being mounted in the car due to access.

8. Ensure the motor connector o-rings are clean and use your plastic compatible grease to lube them.

9. For good measure you can use some battery terminal grease on the motor connector prongs to ensure good conductivity.

10. Reassemble the actuator and reconnect the electrical jack.

11. Turn you ignition on full (no need to start engine) and check whether the actuator is making a high pitched tone. If it is, disconnect and reconnect the jack a few times until this stops to reset the motor.

12. Clear your fault codes as the car should now be fixed.

13. Enjoy not having to pay for a new turbo to be fitted which is the default procedure for this fault at a main dealer.

It should be noted this error is different to the closely related P334B error code which reflects a mechanical problem with the turbo bypass valve becoming obstructed.
Would you post the exact screwfix bit I need please?
 
Jan 30, 2021
9
0
FIX FOR P334A ISSUE…

Having had a couple of 1.2 TSI cars that have demonstrated this fault and investigated further, it seems there’s a design flaw with the turbo actuators on this engine (located just to the right of the exhaust heatshield and mounted on the turbo). The internal position sensor’s plastic slides wear out and this extra slop allows the moving part of the sensor to become jammed at a self-locking angle to the fixed housing. To remedy this:

1. Purchase a 5 lobe security star drive set from Screwfix for about £20 to enable you to undo the 3 anti-tamper screws on the actuator. You'll also need some plastic grease (brake calliper grease will be fine) and spray on lube (must be high temperature & plastic compatible such as silicone or PTFE based - metal lubes may kill the plastics!!).

2. Undo the electrical connector on the actuator by pushing down on the jack whilst gently lifting the tab on the right (fingernails work best if you have them long enough but be careful as these connectors are notorious for becoming brittle and snapping. If this happens you’ll need a small zip tie to hold the connector together when you’re finished). When you see the clip release you can then lift off the jack.

3. Undo the 3 anti-tamper screws (receiving holes circled in picture in picture - two at the top and one slightly hidden at the bottom towards the front of the car) being careful not to drop them.

View attachment 10280

4. Separate the two main halves of the actuator by sliding the black plastic housing to the right. It has runners to keep everything aligned so you'll need to slide it a good distance before it's fully separated but there should be room in the engine bay to do so.

5. Using a small flathead screwdriver, lift the retaining tab up from the top of the position sensor (circled in image) and the moving part of the sensor should now spring away from the housing but still be retained by the spring.

View attachment 10281

6. Use your plastic compatible grease to lubricate the slides on either side of both the moving parts and housing of the sensor being very careful not to stress & deform the spring. Also grease the boss the spring sits on and then re-clip the moving part back into the housing.

7. Use your plastic compatible grease to lubricate the teeth on all the gears on the other half of the actuator (i.e. the sub-assembly remaining mounted on the car). Ask a friend to hold a small mirror and a torch and spray your plastic compatible lube around the metal slide and spring parts to the left of the gears as you won’t be able to get grease on there with it still being mounted in the car due to access.

8. Ensure the motor connector o-rings are clean and use your plastic compatible grease to lube them.

9. For good measure you can use some battery terminal grease on the motor connector prongs to ensure good conductivity.

10. Reassemble the actuator and reconnect the electrical jack.

11. Turn you ignition on full (no need to start engine) and check whether the actuator is making a high pitched tone. If it is, disconnect and reconnect the jack a few times until this stops to reset the motor.

12. Clear your fault codes as the car should now be fixed.

13. Enjoy not having to pay for a new turbo to be fitted which is the default procedure for this fault at a main dealer.

It should be noted this error is different to the closely related P334B error code which reflects a mechanical problem with the turbo bypass valve becoming obstructed.
Tried this didn't work for me
Any other things I can try?
Been reading brake switch can cause problems ?
 
Feb 14, 2021
2
1
Hi, I have just seen this post and as I have just had a similar problem yesterday it got my interest.
My car a Rapid Spaceback 1.2 tsi se sport lost power yesterday, first the EPC light came on then the check engine light,
on plugging in VCDS it came up with p334b mechanical fault so I unbolted the two actuator fixing nuts and pulled the unit away from the housing where it mounts so that that rod which goes to the waste gate was pulled further out of the actuator, I think it had been stuck so I gave it a good spray with penetrating oil working it in and out till it seemed to be free, refastened it and cleared the dtc's.
road tested and had no more bother yet. Will keep you informed.
I thought the article on repairing the actuator was very good as I was a motor mechanic for 49 years and you learn something new every day. By my research it would seem that p334a code is for an electrical fault which the ecu can verify with its feed back from the position sensor and it checks for a mechanical fault by monitoring the output from the manifold and air charge pressure sensors as the actuator opens and closes the waste gate.
Hope this helps somebody.
 

csh

Active Member
May 5, 2018
9
2
United Kingdom
Unfortunately I had the P334A issue pop up again around Christmas.
Once more, I lubricated the part - this worked for another month and then the problem came back again.

I've now taken the step of replacing the wastegate actuator module (found on Seat Direct Parts).
The fault codes were cleared before installation and since installation, have not come back.
Will follow up here after some extended journeys (once we're out of lockdown :oops:) to update on whether this fixes the issue permanently.
 
Jan 30, 2021
9
0
Unfortunately I had the P334A issue pop up again around Christmas.
Once more, I lubricated the part - this worked for another month and then the problem came back again.

I've now taken the step of replacing the wastegate actuator module (found on Seat Direct Parts).
The fault codes were cleared before installation and since installation, have not come back.
Will follow up here after some extended journeys (once we're out of lockdown :oops:) to update on whether this fixes the issue permanently.
[/QUOTE
Has this still worked for you ?
I thought you couldn't just change actuator as it has to be calibrated ?
 
Feb 14, 2021
2
1
If anyone has access to VCDS in can be calibrated with this software.
Go to engine, basic settings and into the dropfown list which pops up, it is in that list.
Just click on it and it goes through the procedure.
I've just done it on mine.
 
  • Like
Reactions: YORKSHIRE777
Jan 30, 2021
9
0
If anyone has access to VCDS in can be calibrated with this software.
Go to engine, basic settings and into the dropfown list which pops up, it is in that list.
Just click on it and it goes through the procedure.
I've just done it on mine.
Ok thanks for that don't know anyone vcds though
Where is cheapest for actuator? Just dealer ?
 

csh

Active Member
May 5, 2018
9
2
United Kingdom
I didn't do any calibration of any sort.. I just used a bluetooth OBD reader to reset the error code before fitting the new part.
During fitting, I needed to move the rod manually out to bring it into alignment with the reciprocal part on the turbo, then fit the clip that holds rod to the turbo.

After fitting, I found the part moves back and forth fine without any need for calibration (I can hear it working fine when switching off the engine).
No error codes or lights have come up since.
 
  • Like
Reactions: YORKSHIRE777
Jan 30, 2021
9
0
I didn't do any calibration of any sort.. I just used a bluetooth OBD reader to reset the error code before fitting the new part.
During fitting, I needed to move the rod manually out to bring it into alignment with the reciprocal part on the turbo, then fit the clip that holds rod to the turbo.

After fitting, I found the part moves back and forth fine without any need for calibration (I can hear it working fine when switching off the engine).
No error codes or lights have come up since.
Any ideas of cheapest place for actuator?
Or just nearest dealer ?
Thanks 👍
 
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