My Galaxy MK2 (WA6) started slipping gears a few days back and now it's fine for a couple of hundred meters, then starts slipping gears and then goes into "Transmission Limited Function." I think the transmission is a 6DCT450 MPS6.

It has the following fault codes:

1. P2714 - Pressure Control Solenoid D Performance / Stuck Off
2. P170F - Clutch Pressure Release Valve Failed

So I figured low or dirty fluid was most likely, so I decided to drain and refill the transmission oil... simple enough.

I unscrewed the level check plug first thinking that nothing should come out, but a good 2-3 litres came out all over my garage floor... that was stupid, but surprised me because IMO nothing should really have come out.

Then I fully drained it (a good 6.5 litres altogether) and filled it up again... after driving it for 200 metres it started slipping and failed again.

So now I feel even more stupid because I didn't change the filter and, because it's fine for the first couple of hundred metres and the fact that so much oil came out through the level check hole this is looking to me like a badly blocked filter.

I honestly can't afford to take it to a garage or buy a new car, so I really need to deal with this.

So, two questions:

1. Does this sound like a clogged filter to you?
2. Can the filter be changed without first draining the transmission oil? I don't want to buy more if I don't need to.

Do you know the correct process to change the oil and filter?

When removing the side plug (I don't call it a level plug!) maybe 500 ml normally comes out - this is perfectly fine and doesn't mean it is overfilled (2-3 LITRES implies grossly overfilled but I don't know how that much could ever be put in unless someone has been really silly!) It is a 2 chamber system with the front (1) being the mechatronic and the rear (2) a "standard" 6 speed gearbox with synchronisers and forks etc. The 2 clutches are also operated by oil pressure:

As part of the process, you have to get the front chamber filled which floods over until the oil comes out of the side plughole.

The external filter only takes oil from the transmission, filters it and supplies it to the mechatronic, solenoids, operating pistons for the gearchange forks, clutches etc.

Those codes do sound serious (presumably read with Forscan?) they imply problems with a solenoid and relief valve (as indicated)

Before you get into expensive work, I'd first of all change the filter ( no oil should come out other than the small amount that's in the casing and the new one should be filled with oil as it is refitted) THEN check the level using the correct procedure THEN pull the old filter apart and look for debris (specifically the dreaded plastics or otherwise)
Once you've done that and come back with the results there may be further advice or at least diagnosis suggestions.

If you need the correct level check process, please ask or look here (you can ignore the draining bit):
https://www.youtube.com/watch?v=CERqRSK2SWM

 

1 hour ago, MikeRatcliffe said:

Can the filter be changed without first draining the transmission oil? I don't want to buy more if I don't need to.

I'm not familiar with the details your specific trans, but on the odd occasion I've seen a mechanic changing a trans filter it's always involved removing part of the trans case to get to it, which has naturally involved the fluid coming out. Even if it was an external filter like on the engine though, the filter should be full of fluid when you take it off, which you'll want to replace anyway.

This diagram does show an external filter:

However, I also found the following video, and at 9:37 this external filter is shown, but the guy mentions that there's also an internal one that you have to take the transmission apart to get to.

Interestingly he'd also chasing a 'transmission limited' warning, and from the suggested videos youtube lists, there seems to be a whole series of follow up videos.

You should perhaps get yourself forscan to check what fault codes are present in the vehicle which may help guide your quest to identify and fix the source of your problem. Edit: sorry, forgot you'd already listed codes. 🤣

1 hour ago, MikeRatcliffe said:

Does this sound like a clogged filter to you?

Was the vehicle on a flat level surface when you did it?

On 5/29/2025 at 4:11 PM, Shearers said:

Before you get into expensive work, I'd first of all change the filter ( no oil should come out other than the small amount that's in the casing and the new one should be filled with oil as it is refitted) THEN check the level using the correct procedure THEN pull the old filter apart and look for debris (specifically the dreaded plastics or otherwise)
Once you've done that and come back with the results there may be further advice or at least diagnosis suggestions.

So, I have changed the filter... much easier than I expected.

There was no plastic or metal in the filter, which I suppose is a good thing.

The oil level is good.

It still keeps switching to "Transmission Limited Function" quickly... especially if I try to go up a hill (a hundred or so metres away).

Switching the ignition off for a few seconds and back on again resets the problem and it drives again for another minute or so.

What should I do next?

On 5/29/2025 at 3:02 PM, MikeRatcliffe said:

• P2714 - Pressure Control Solenoid D Performance / Stuck Off
• P170F - Clutch Pressure Release Valve Failed

Good to have confirmed that level is correct and filter clear.

What is the history, how many oil changes has it had and what is the mileage - the damage may already have been done (but I need to know)?

If you are still getting these "hard codes" when the fault is on then all I can suggest is to look at all of the transmission related parameters (PIDs, Parameter IDs) in Forscan to try to collect as much info as possible as it is now looking like you may need some specialist help or it needs to come apart but not yet...
On ours, there are several solenoid currents (demanded and actual), temperature, shaft  speed, shift position, park position etc.

I'd record all of these with fault on and off, try to see if it will work in manual mode and what happens to the PIDs (get someone to monitor whilst you drive (safety or Forscan can, I believe, record but never done it)

This is with a view to anyone here having a Magic Wand but otherwise it looks like there are problems with the solenoids (hence the need to look for the demanded not being the same as the actual and all the options round that).

I think the mechatronic can be removed without taking the box out (from the front, again, never done it and probably wouldn't attempt)

The other alternative is to present your results to an expert see what they say and decide from there.
If no one on here has any better ideas I'd look for automatic transmission specialists in your area something like this (with a long guarantee as it won't be cheap, but any warranted repair may still be cheaper than changing as long as there are no other issues on the horizon. CAR = Cash Always Required, sorry😞

https://austrin-engineering.co.uk/services/#1488725417825-2758920e-e7efd3eb-d2400966-8526

3 hours ago, Shearers said:

What is the history, how many oil changes has it had and what is the mileage - the damage may already have been done (but I need to know)?

130,000 miles (diesel, so not massively high) and the transmission oil has been changed every 30,000 miles. We have a great automatic specialist in Kettering (Midland Automatic Transmissions), who are really well respected.

The car's only worth 3,000 when it's working, so as long as the transmission would cost less, I suppose that would be the route.

3 hours ago, Shearers said:

If you are still getting these "hard codes" when the fault is on then all I can suggest is to look at all of the transmission related parameters (PIDs, Parameter IDs) in Forscan to try to collect as much info as possible as it is now looking like you may need some specialist help or it needs to come apart but not yet...
On ours, there are several solenoid currents (demanded and actual), temperature, shaft  speed, shift position, park position etc.

I'd record all of these with fault on and off, try to see if it will work in manual mode and what happens to the PIDs (get someone to monitor whilst you drive (safety or Forscan can, I believe, record but never done it)

Yeah, the obvious suspect now is the "Pressure Control Solenoid D".

I should also check the continuity of any wires that might be worn because they can apparently easily get damaged.

I really like the idea of gathering the values using Forscan, especially at the point of failure.

I also like the idea of trying manual mode... I never really considered that as it could help narrow things down a bit more.

I'll post the results here in case we can narrow it down further.

I'm super grateful for your help, thanks!

That does sound like a plan to get as much information as possible to help you and/or your local specialist to be confident in agreeing a solution - exactly what we'd do.

I'd go further (as we were offered £50 trade in for ours!) and, perhaps like yourself it is worth far more to us as we can't find anything else that comes close (it has taken us all over Europe with a caravan on the back).
If the cost of the repairs could be written off over say 3 or 4 years then it would still be "cheap" motoring comparing to the cost to change (and value as it is at the moment likely very low?)
Just trying to allow you to generate options and make a decision that's right for you.

Unsure if you are based on Mk4 or 5 Mondeo but Alan has worked on both when used as taxis but only one of his videos refers to Powershift oil change):

https://www.youtube.com/watch?v=_iPoz6hf96Q&t=79s

https://www.youtube.com/watch?v=NnJAn0izK58

https://www.youtube.com/watch?v=AXddHJJdaLE

 

On 5/31/2025 at 7:24 PM, Shearers said:

On ours, there are several solenoid currents (demanded and actual), temperature, shaft  speed, shift position, park position etc.

I'd record all of these with fault on and off, try to see if it will work in manual mode and what happens to the PIDs (get someone to monitor whilst you drive (safety or Forscan can, I believe, record but never done it)

Yep, so it works a lot better manual mode, although it struggles to drop from 2nd to 1st... wouldn't dare try a longer journey though.

Here's the values that I have captured (see attachment).

Headings
PCSDCD,A: Pressure Control Solenoid D (Expected Value)
PCSDCM,A: Pressure Control Solenoid D (Actual Value)
APP: Accelerator Pedal Position
APP_D: Accelerator Pedal Position D
GEAR_SEL Currently selected gearbox gear
KDS: Kick Down Switch
SIV,V: Switched Ignition Voltage

The gear slipping happened at 75 seconds and 96 seconds.

Notes
PCSDCD and PCSDCM values match throughout the journey.
GEAR_SEL jumps into neutral when the slipping happens.
SIV is fairly constant.
KDS was active, but not every time there was slipping.
APP & APP_D appear to match the throttle positions.

Not sure what to make of all this though.

Weird that it jumps into neutral with other parameters (to me) being consistent and perhaps acceptable???
Asking again if cable adjustment on lever is in correct position as D is next to N -that is my initial reaction?

Drop from 2 to 1 is likely to be difficult as 1 is very low.
If it doesn't jump out in manual mode then it may be quite a clue because manual works on an electrical system rather than the cable position.

Kickdown switch  doesn't look active on your graphs (part of throttle switch - what is that saying could it be an issue)?
And if it jumps to N then it's not slipping, it's in neutral???
But are the fault codes still the same and hard as I don't understand that ...yet. I know I'm guessing which I don't like but that's the best shot before anything expensive?

Does this match up at all:

and:

1 hour ago, Shearers said:

Kickdown switch  doesn't look active on your graphs (part of throttle switch - what is that saying could it be an issue)?

It doesn't kick in because I am trying to be gentle 😉

At 97 - 99s (between 2 neutrals) it moves into 4th, but Forscan's chart doesn't show it... probably a bug.

So it goes:

• Neutral
• 4th gear for 2 seconds
• Neutral

Apart from that it goes betwen neutral, 1st and 2nd (transmission limited function uses 2nd gear).

I figured that it throws it into neutral because of some error condition, but you are right... the values all look fine.

I'll check the gear selection in the morning... if it's something that simple, then I'll be more than happy!

 

I think all you (we?) can do is to check everything as far as possible then if that doesn't work it will likely need to be stripped and when that far down no sense in only doing the bare minimum.
It does appear (if manual mode works 100%?) that the mechanical bits are fine so may get away with mechatronic work (clean, solenoids, internal filter etc.)
This would depend on warranty from specialist and their advice if it comes to that.
I'd definitely keep clear records and give them all of the information collected plus retain receipts as, even if it eventually went for scrap, the gearbox could well be sold on with that evidence?

Looking forward to the next thrilling instalment.....

The idea about checking wiring continuity was the best one yet.

If it works slightly better in manual mode but not auto mode then I'd have to suspect a COMMs wire gone/going down somewhere or even a TCM issue (but not until you've proved out the wiring)

Especially as the filter removal didn't throw any debris👍

Check earthing performance is good too

@DaveT70, Thanks, my understanding is that gearlever cable goes to magnetic disc inside box and a sensor detects P R N D which is auto mode (i.e. no external wiring involved)

Whereas manual sends it's instructions via CAN  which does involve signals that have to go via wiring that passes from car via plug. 

To me, if it works in manual mode, without dropping to neutral, which seems to be the issue, that says the mechanical bits and whatever section of the TCM is involved is OK?

Strangely, solenoids have to be involved too which seem to be the hard fault codes mentioned above - don't understand that unless those specific ones are not involved in manual mode?

You can tell I'm floundering to understand (!) but hopefully all of the evidence amassed will allow @MikeRatcliffe to have enough to help make a sensible decision, unless he comes back with a revelation in his next post which would be good.

It's still lever setting, wiring and earthing to be certain of before taking it apart?

12 hours ago, Shearers said:

Thanks, my understanding is that gearlever cable goes to magnetic disc inside box and a sensor detects P R N D which is auto mode (i.e. no external wiring involved

Weather you are in D or Manual mode the gearbox lever will be in DRIVE, the shift signals still come from the TCM, just differently 

The solenoid codes could be because they have no signal to respond to, but are being requested

Definitely, the OP should have all the wiring checked

48 minutes ago, DaveT70 said:

Definitely, the OP should have all the wiring checked

I think we have given @MikeRatcliffe the best possible things to check, information to pass on if necessary.

Hope it can be fixed and he comes back with the final solution. I  don't think we can do much more, thanks?

Yep, after a longer drive yesterday it's clear that it also struggles in tiptronic mode... it accelerates very slowly and any time the gearbox tries to be smart, like going uphill, the gears start slipping and it goes into limited function.

I went to a specialist and they're pretty sure it's gonna be a rebuild... not happy, but without opening the box they won't really know what the problem is.

Anyhow, I just wanted to say thanks for your help.

Still check the wiring BEFORE you commit to a rebuild as the same faults will be there after the rebuild

3 hours ago, DaveT70 said:

Still check the wiring BEFORE you commit to a rebuild as the same faults will be there after the rebuild

Agree totally, sorry to nag... check everything external to ensure there's nothing wrong there plus pass on all of your evidence so that there is a full picture of all your fault finding but obviously need to accept specialist judgement to get their (long) guarantee.
Hope fully, you can get it sorted and, as said, maybe you can get away with a mechatronic overhaul only, depending on what is found (I'd certainly consider getting the internal filter and magnets cleaned)

If clutches have been slipping for any length of time, or any doubt as to their condition they will likely need work which should give a long term fix.
It's expensive but cheaper than cost to change...
Do let us know how you get on!

Ouch... the garage has just quoted me £3,808.40 + VAT (20%) = £4,570.08

Now I feel sick!

3 hours ago, MikeRatcliffe said:

Ouch... the garage has just quoted me £3,808.40 + VAT (20%) = £4,570.08

Sorry to hear that, I thought more around the pre VAT price but everything seems to be going stupid.
My go  to specialist if it happened to me offer 2 year warranty with Ts & Cs (which I don't know):
https://austrin-engineering.co.uk/services/

What are they proposing to do, exactly and what warranty is offered?

It's 2015 so plenty of life left if you can write that off over multiple years rather than get nowt as a trade in and pay inflated price for a change?

17 hours ago, Shearers said:

Sorry to hear that, I thought more around the pre VAT price but everything seems to be going stupid.
My go  to specialist if it happened to me offer 2 year warranty with Ts & Cs (which I don't know):
https://austrin-engineering.co.uk/services/

Perfect, but a bit of a journey from Corby... I'll have to shop around because almost 4 grand before VAT seems massively expensive to me.

17 hours ago, Shearers said:

What are they proposing to do, exactly and what warranty is offered?

It would be a full rebuild with a 12 month / 12,000 mile warranty

17 hours ago, Shearers said:

It's 2015 so plenty of life left if you can write that off over multiple years rather than get nowt as a trade in and pay inflated price for a change?

Yeah... a replacement would cost quite a bit more than that and with a reconditioned transmission it puts it above most second hand Galaxies on the market.

1 hour ago, MikeRatcliffe said:

Yeah... a replacement would cost quite a bit more than that and with a reconditioned transmission it puts it above most second hand Galaxies on the market.

I was giving the company only as an example of their warranty.
Again, sorry to nag but has wiring been checked, just in case...
It is a pretty difficult decision but if you like the car then with that repair it should go for many more years.
I'd be asking about the enhanced parts (especially dreaded clutch plastics) that would be fitted and will solenoids, pistons,  internal filter etc. be replaced also?
What else is similar - nothing (beware, rant to follow!)?  - All roads lead to SUVs which often have stupid transmission tunnel and no real third seat in 2nd row plus smaller overall boot capacity unless you go massive plus you still don't get "step in" where seat height from floor means you can sit and put your feet flat on the floor whilst upper legs are still on seat squab (if you get my drift?)
If there are any alternatives (we know about Touran, Sharan and clones, Tourneo Connect 7 seat, plus Berlingo etc  -  not big enough for our caravan) then do let us know?

A recovery vehicle collected my Galaxy yesterday to take it to Driver Transmissions (Moseley Rd, Birmingham). They have a decent reputation and quoted £2,950 + VAT, which is more what I would have expected.

Fingers crossed that they do a decent job.

... less than a day later they called to say it's done. They just stuck a new transmission in. Didn't expect it to be that fast.

Sounds good (ish)?
They may have just used a reconditioned transmission then yours will be reconditioned for the next person that needs one?
I suggest you a) ask them exactly what has been used, b) get it all in writing and add to your records, c)Keep all receipts d) Check their warranty conditions which are...?
I'd also mark up the transmission as "Reconditioned July 2025" in paint or something so that it is obvious when you sell or it is scrapped.

BUT, hopefully it is fixed and you are happy with it again?

That's just me.
 

3 hours ago, Shearers said:

They may have just used a reconditioned transmission then yours will be reconditioned for the next person that needs one?
I suggest you a) ask them exactly what has been used, b) get it all in writing and add to your records, c)Keep all receipts d) Check their warranty conditions which are...?
I'd also mark up the transmission as "Reconditioned July 2025" in paint or something so that it is obvious when you sell or it is scrapped.

Yes, it's a reconditioned 2nd gen transmission, which don't use the plastic clips.

It has a 12 month warranty with unlimited miles.

I love the idea of somehow marking the transmission as reconditioned by the way.