Hi all,

My family recently bought a 2013 Ford Grand C-max diesel Automatic at 76k miles that appeared to be in flawless condition with a cambelt, water pump changed and a full transmission service in late 2024, however, 2 days of owning it we've been having transmission issues. I'm very confused because it was so sudden! I scanned the car's computer before we brought it with no codes, in the test drive the engine was opened up and went through all the gears, the car was shifting and driving flawlessly, which is the reason we brought it before knowing what these 6DCT450 transmission Powershifts are like. We drove over an hour home back and the car was working perfectly the next 2 days, parked it for the night, only for it to be started in the morning and 'Transmission Function Limited' to show up.. tried to see if the car moved and had to give it quite a few revs to move since it was on slight hill, I believe it was in 2nd gear limp mode and reverse worked also. Parked up and began to do research of what it good be, however, the next day, drive did not work, then the day after that reverse stopped working and since then even park stopped working, now the car is only held by the handbrake! It's very confusing for the car to stop working so suddenly, stopped working when not even being used and driven, reverse and park gradually stop working too without even being driven at all! The night it first had issues, it was -5 degrees C out and has been very cold since, if that could have anything to do with it?

I got my OBD2 scanner out, used FORscan to see a bunch of intermittent and active codes across multiple modules, so I was hoping it was electrical and not anything majorly wrong with the transmission. Codes below:

===OBD2_TCM DTC P0766-P===
Code: P0766 - Shift Solenoid D Performance or Stuck Off

Status (-50):
 - Pending - malfunction is expected to be confirmed 

Module: On Board Diagnostic II (TCM)

Diagnostic Trouble Code details

SSD or SSPCD Performance or Stuck Off

===OBD2_TCM DTC P0771-P===
Code: P0771 - Shift Solenoid E Performance

Status (-50):
 - Pending - malfunction is expected to be confirmed 

Module: On Board Diagnostic II (TCM)

Diagnostic Trouble Code details

SSE or SSPCE Performance or Stuck Off

===END OBD2_TCM DTC P0771-P===

===OBD2_PCM DTC U0415-C===
Code: U0415 - Invalid Data Received from the ABS Control Module

Status (-43):
 - Confirmed - malfunction is confirmed 

Module: On Board Diagnostic II (PCM)

===END OBD2_PCM DTC U0415-C===

===TCM DTC P0766:00-24===
Code: P0766 - Shift Solenoid 'D' Performance/Stuck Off

Status (-24):
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Transmission Control Module

 Freeze Frame  #1:
-EVENT_TIME: 398932679 s (Tue Jan 06 17:43:45 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 14.8 V - Control Module Voltage
===END TCM DTC P0766:00-24===

===TCM DTC P0771:00-27===
Code: P0771 - Shift Solenoid 'E' Performance/Stuck Off

Status (-27):
 - DTC Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Transmission Control Module

 Freeze Frame  #1:
-EVENT_TIME: 398932677 s (Tue Jan 06 17:43:43 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 15.0 V - Control Module Voltage
===END TCM DTC P0771:00-27===

===PCM DTC P1637:64-2C===
Code: P1637 - CAN Link ECM/ABS Control Module Circuit/Network

Additional Fault Symptom (:64):
 - Signal Plausibility Failure

Status (-2C):
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

 Freeze Frame  #1:
-EVENT_TIME: 399023165 s (Wed Jan 07 18:51:51 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 14.8 V - Control Module Voltage
===END PCM DTC P1637:64-2C===

===PCM DTC U0418:08-2C===
Code: U0418 - Invalid Data Received from Brake System Control Module 'A'

Additional Fault Symptom (:08):
 - Bus Signal/Message Failures

Status (-2C):
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

 Freeze Frame  #1:
-EVENT_TIME: 399023165 s (Wed Jan 07 18:51:51 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 14.8 V - Control Module Voltage
===END PCM DTC U0418:08-2C===

===PCM DTC P1719:08-2C===
Code: P1719 - Engine Torque Signal

Additional Fault Symptom (:08):
 - Bus Signal/Message Failures

Status (-2C):
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

 Freeze Frame  #1:
-EVENT_TIME: 399023120 s (Wed Jan 07 18:51:06 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 14.8 V - Control Module Voltage
===END PCM DTC P1719:08-2C===

===PCM DTC P193C:48-2C===
Code: P193C - Steering Wheel Angle Signal

Additional Fault Symptom (:48):
 - Supervision Software Failure

Status (-2C):
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

 Freeze Frame  #1:
-EVENT_TIME: 399023120 s (Wed Jan 07 18:51:06 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 14.8 V - Control Module Voltage
===END PCM DTC P193C:48-2C===

===PCM DTC U0415:86-AC===
Code: U0415 - Invalid Data Received From Anti-Lock Brake System (ABS) Control Module

Additional Fault Symptom (:86):
 - Signal Invalid

Status (-AC):
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is On for this DTC

Module: Powertrain Control Module

 Freeze Frame  #1:
-EVENT_TIME: 398938538 s (Tue Jan 06 19:21:24 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 14.8 V - Control Module Voltage
===END PCM DTC U0415:86-AC===

===PCM DTC P068A:00-2C===
Code: P068A - ECM/PCM Power Relay De-Energized Performance - Too Early

Status (-2C):
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

===END PCM DTC P068A:00-2C===

===APIM DTC None===
Successful DTC reading, no error codes found

Module: Accessory Protocol Interface Module

===END APIM DTC None===

===SASM DTC None===
Successful DTC reading, no error codes found

Module: Steering Angle Sensor Module

===END SASM DTC None===

===ABS DTC None===
Successful DTC reading, no error codes found

Module: Antilock braking system

===END ABS DTC None===

===RCM DTC None===
Successful DTC reading, no error codes found

Module: Restraint Control Module

===END RCM DTC None===

===PAM DTC None===
Successful DTC reading, no error codes found

Module: Parking Aid Module

===END PAM DTC None===

===PSCM DTC None===
Successful DTC reading, no error codes found

Module: Power Steering Control Module

===END PSCM DTC None===

===BCMii DTC B110C:87-28===
Code: B110C - Rear door driver side power child locking motor

Additional Fault Symptom (:87):
 - Missing Message

Status (-28):
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Body Control Module

 Freeze Frame  #1:
-EVENT_TIME: 399024283 s (Wed Jan 07 19:10:29 2026) - Event time
-TOTAL_DISTANCE: 123772 km - Total Distance
-MODULE_VOLTAGE: 13.3 V - Control Module Voltage
===END BCMii DTC B110C:87-28===

===FCDIM DTC U0193:00-08===
Code: U0193 - Lost Communication With Digital Audio Control Module A

Status (-08):
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Front Control/Display Interface Module

===END FCDIM DTC U0193:00-08===

===FCDIM DTC U0253:00-08===
Code: U0253 - Lost Communication With Accessory Protocol Interface Module

Status (-08):
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Front Control/Display Interface Module

===END FCDIM DTC U0253:00-08===

===FCDIM DTC U3006:16-08===
Code: U3006 - Control Module Input Power 'A' Circuit / Open

Additional Fault Symptom (:16):
 - Circuit Voltage Below Threshold

Status (-08):
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Front Control/Display Interface Module

===END FCDIM DTC U3006:16-08===

===FCDIM DTC U0155:00-08===
Code: U0155 - Lost Communication With Instrument Panel Cluster (IPC) Control Module 'A'

Status (-08):
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Front Control/Display Interface Module

===END FCDIM DTC U0155:00-08===

===PDM DTC None===
Successful DTC reading, no error codes found

Module: Passengers Door Control Unit

===END PDM DTC None===

===DDM DTC U2013:87-28===
Code: U2013 - Switch Pack

Additional Fault Symptom (:87):
 - Missing Message

Status (-28):
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Drivers Door Module

===END DDM DTC U2013:87-28===

===ACM DTC U0257:00-28===
Code: U0257 - Lost Communication With Front Controls/Display Interface Module

Status (-28):
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Audio Control Module

 Freeze Frame  #1:
-EVENT_TIME: 398583774 s - Event time
-TOTAL_DISTANCE: 123702 km - Total Distance
-MODULE_VOLTAGE: 8.5 V - Control Module Voltage
-INCAR_TEMPERATURE: 23 °C - In car temperature
===END ACM DTC U0257:00-28===

===IPC DTC None===
Successful DTC reading, no error codes found

Module: Instrument Panel Control Module

===END IPC DTC None===

I did some research and saw that a bad battery can cause these issues, because the car did have to be jump started when we bought and I assumed it was alright since the car was not being used. I tested the battery being at 11.9 volts and self-discharging to that even under no load after charging it, so we then got a new battery installed by the AA and they programmed the new battery in. Cleared the codes, however, the transmission ones remained and changed to P284A - Selector Fork B Component Sticking and P284B Selector Fork C -Component Sticking. On the other hand, the next day, all the previous codes across many different modules previously came back again, however different transmission codes, so I'm thinking some sort of electrical issue? I measured the battery voltage and it was 12.1 volts, so I was suspecting possibly a parasitic draw also? I used FORscan to clear the codes after running the engine for a little, and I reset the TCM whilst the engine was running and the car jolts, then the sensors state when I go in reverse the transmission goes into reverse, and in drive it goes into 2nd gear, but the car still doesn't move in either gear and after I put it in park the gearbox stays in neutral regardless of where the gear stick is, and I have to reset the TCM whilst the engine is running to make it do that again and the transmission codes change each time, once changing to Shift Fork A Stuck and Shift Fork C stuck, but then after another reset only one transmission code P0766 Solenoid D Performance or Stuck Off. I checked the ground voltage at the transmission which was 12.1 to 12.5 volts and the resistance to the battery ground was around 1 ohm. I disconnected the TCM connector which was clean and measured voltages at each of the pins some having 12.5 volts, but then others ranging from 9 to 10 volts, however, when I switch around my test leads with one on the connector and the other on either the ground or positive I get around 1 to 5 volts, I'm not sure if this is normal since I can't find a proper pinout. I checked all the fuses from all the fuse boxes in the car and none of them were blown and I measured 12.5 to 12.7 volts on each fuse box with the ignition off.

To make this even more confusing, intermittently, whilst the engine is running I am getting a code for PSCM sensor Steering Wheel Angle Signal invalid and when I check the value of this sensor it says 5766.0 degrees, which doesn't change when I turn the steering wheel and I'm definitely sure that value is invalid..also, when I press the brake pedal with the engine running, I am unable to communicate with the ABS module, and FORscan tries to read its DTCs it just says error, but as soon as I let go of the pedal, it reads. Moreover, when I put the gear selector in drive, the brake pedal becomes really really firm and stiff, but in any other gear selection it goes back to being normal or slightly squishy where I am able to put it to the floor with a good amount of force. 

I contacted some transmission specialists over the phone and gave the codes, and as soon as I said the word Powershift they said it needs a new transmission and quoted £3500 to replace it! I'm concerned this maybe an electrical issue, ABS issues or some other transmission issue I have no clue what to do. There is so many possible things, I'm not sure what to check next or how to go about this. I'm really desperate to try and fix this car for my parents and family so my mom can take my siblings to school, and I really do not want this to be huge loss for us if its something I can fix with a bit of help. Any advice or help would be much appreciated!

Edited January 9Jan 9 by literallyahmadrn

Welcome!
I can only give my suggestions for this VERY complex looking set of issues so don't take as Gospel...
You appear to have a lot of transmission  and communication (U codes) issues.
Is this vehicle under any sort of warranty, if so, take it back?
https://www.citizensadvice.org.uk/consumer/buying-or-repairing-a-car/problems-with-a-used-car/

Otherwise if you are stuck with it then I'd, in parallel, consider
Check the oil level to the correct procedure (not just running out from the side plug which is NOT a specific level plug as there are two chambers) and this will let you see the cleanliness (has it actually been changed) and perhaps consider changing the oil and filter again (rip filter apart to check for contamination i.e. dreaded plastic particles):
https://www.ebay.co.uk/itm/112436788478

Is the battery maintaining its charge - do you have a parasitic draw leading to these electrical issues?
Earth straps?
Then one of the other strands is electrical issues between the PCM and transmission  - multi plugs under wheelarch are common fault areas - need to get the integrity of transmission wiring checked.
BUT you appear to have other communication (CAN?) issues with ABS etc.
If those codes keep coming back, there's another issue that needs bottoming (again, perhaps wiring?)

Sounds like you need a good auto electrician if you can't DIY and, until proven otherwise, I'd ignore the "You need a new transmission"  suggestion as it appears to lack any sort of evidential basis (at the moment)

Getting rid of the multiple electrical issues first then a focus on transmission oil/filter/wiring could be a way forward ?

7 hours ago, Shearers said:

Welcome!
I can only give my suggestions for this VERY complex looking set of issues so don't take as Gospel...
You appear to have a lot of transmission  and communication (U codes) issues.
Is this vehicle under any sort of warranty, if so, take it back?
https://www.citizensadvice.org.uk/consumer/buying-or-repairing-a-car/problems-with-a-used-car/

Otherwise if you are stuck with it then I'd, in parallel, consider
Check the oil level to the correct procedure (not just running out from the side plug which is NOT a specific level plug as there are two chambers) and this will let you see the cleanliness (has it actually been changed) and perhaps consider changing the oil and filter again (rip filter apart to check for contamination i.e. dreaded plastic particles):
https://www.ebay.co.uk/itm/112436788478

Is the battery maintaining its charge - do you have a parasitic draw leading to these electrical issues?
Earth straps?
Then one of the other strands is electrical issues between the PCM and transmission  - multi plugs under wheelarch are common fault areas - need to get the integrity of transmission wiring checked.
BUT you appear to have other communication (CAN?) issues with ABS etc.
If those codes keep coming back, there's another issue that needs bottoming (again, perhaps wiring?)

Sounds like you need a good auto electrician if you can't DIY and, until proven otherwise, I'd ignore the "You need a new transmission"  suggestion as it appears to lack any sort of evidential basis (at the moment)

Getting rid of the multiple electrical issues first then a focus on transmission oil/filter/wiring could be a way forward ?

Hello!

Thank you so much for your reply!

I contacted Ford and put the vehicle details in and unfortunately the car has no warranty.

I tested for a parasitic draw, which was negative drawing about 20 to 30 milliamps - I assume maybe the battery was lower the morning after it was installed. The voltage reading on FORscan, when the engine was running was 15.1 volts, but then went down gradually to around 13 to 14 volts, is that normal, because I heard that above 15 volts can damage the battery? I intend to check the fluid level how you've stated, but I believe I need to go under the car, which I'm unable to do at the minute due to where the car is, I will let you know the result as soon as I have the opportunity. I saw some hose connectors on the top of the external transmission filter, would it be a good a idea to disconnect one of them to take a sample of transmission fluid, or is that not a good idea and is it pressurized?

I've cleaned all the battery terminals, main big wires to the battery, engine ground, transmission ground, ensured there is no corrosion on the TCM connector or main engine fuse box cable connector, checked the larger Maxi fuses in front of the battery and cleaned all corrosion, the power steering one being very rusty. All the codes did not come back after clearing them so far, except the transmission codes. The transmission codes keep changing to different ones, but commonly keep staying as P2849 - Shift Fork 'A' Stuck and P284B - Shift Fork 'C' Stuck, but I've had no solenoid ones come back so far either, and it did change to just having a code for Shift Fork B being stuck, but then that disappeared also and the car still does not move at all in either gear regardless of the code I have. Moreover, I did also get a new transmission code that came up a few times then disappeared being P0603 - Internal Control Module Keep Alive Memory (KAM) error.

I plan to also check the multi-plugs you stated under the wheel arch, to access that would I just remove the passenger side tyre and remove the wheel arch lining, or is there a different way you are suppose to access it? 

I will definitely suggest an Auto-electrician to my parents like you said and consider replacing the fluid and filter after checking it.

I went on FORscan also, and read the measured and desired current draw readings for each transmission solenoid on a graph and shifted through each gear selection, keeping in mind the only present codes at this time were Shift Fork A and C Stuck, and the measured readings seem really spikey, but I'm not sure whether its normal or it is supposed to be like this, I cannot interpret it if anyone has any ideas; picture of graphs below:

                                                                                                                                                                                                 
 

Again thank you ever so much for your help!

I can't take in the totality of your post, so can only pick out key points I can see and obviously can't be responsible at this distance!

You stated you "recently bought" so the Citizens Advice link may be relevant as it sounds to me like the faults may have been, hidden, present or ready to fail when you purchased - take it up with the seller based on that info if it meets the advice set out.?

I'd definitely NOT disturb the pipes on the external filter to avoid any risk of damage to the O rings but if you removed the filter (there is a little ratchet tab that needs to be carefully bent back to allow it to turn, although it will come off without that if missed) you would see the condition and it will be full of oil.
You are supposed to fill up the filter housing before replacing (16 Nm) so may be worth getting a new filter and oil ready or at least enough to refill or simply pour the oil back in once inspected. Ripping the filter apart should give a good idea of how well it has been looked after, see attached which I think is normal (had 2 like that for the last 2 changes)

It looks like your cleaning has reduced the very large number of electrical /communication codes if I understand correctly, leaving the transmission issues (still looking a bit random)?

I can't make much sense of the graphs but I have looked at my results in table form where I noticed that the demanded and actual solenoid currents were very close values and that's what I think should be observed.

When changing gear (do it in manual to control things better? - is that any different?) the demanded and actual should follow and mirror each other?
My gut feeling is that those spiky readings should definitely NOT be there implying there is still an electrical fault in the wiring somewhere.
Under the wheelarch (remove the liner) there is the PCM which may be in a security bolt protected box  and multiple multi-way connectors.
Ideally a full wiring diagram is needed BUT another member has supplied a diagram of the transmission plug connections that may (or not) be relevant:

 

It may still be an internal transmission fault BUT my suggestion is always to do everything possible external, to rule that out before biting the large bullet and only after detailed discussions on what will be done with a VERY good warranty from any specialist if you have to go that route.

Based on the DTC codes, the main problem is almost certainly a mechanical failure of the DCT450 transmission. The DCT450 units from this era are known to use plastic clutch spring retainers. Due to age and heat cycling, these retainers are known to break or even shatter, allowing plastic particles to spread throughout the entire transmission, including the mechatronic valve body and solenoids. This is a well-known failure mode of the DCT450.

The fact that several shift solenoids and shift forks seem to be affected at the same time makes it highly unlikely that this is an electrical fault and strongly points toward a mechanical contamination issue inside the transmission.

A sensible first diagnostic step would be to drain the transmission oil and pass it through a fine filter or paper towel to inspect for foreign material. If any plastic debris or other foreign objects are found in the oil, this indicates internal mechanical damage and you are likely facing a full transmission rebuild or complete transmission replacement.
 

Only a small number of specialist transmission workshops offer rebuild services for these units using uprated or revised components. Even when available, the costs are typically high, as the repair is time-consuming and requires specialist knowledge and tooling.

Many general transmission specialists will not work on the DCT450 at all, largely due to its notoriously poor reputation and high failure rate.

So, the key suggestion from both is to look at the condition of oil and filter to start to decide from there?
I still say to rule out any warranty or consumer rights if it within the conditions for that as you haven't given details of the sale (more difficult if private but we don't yet know?)

I fully agree.

If there’s a possibility to cancel the purchase, do it immediately, as this car will most likely quickly become a money pit.

I wouldn’t be surprised if the previous owner got rid of it because of these problems.