c320 stuck in 2nd and reverse mode P0778 fault code

[pattiodors]

Hi there, I have a problem with a 2004 c320.
6 months ago I had a problem with the conductor plate which I had changed,
the problem has reappeared but with no fault light on dash. I put my obd reader with the torque app on the car and there was only 1 fault code logged which was P0778 which is pressure control solenoid B - electrical.
Do you think it's the plate again or just a reseating/ replacement of solenoid.
Can I check this solenoid from the plug on the gearbox before pulling the gearbox sump off? or does anyone have the test procedures to check the solenoid?
Thanks for looking

 

[Auto-mobile]

You won't get a warning on the dash, you need to get it on a proper diagnostic machine.

 

[pattiodors]

Thanks for the reply.
Is it worth just clearing ecu code and see what happens as I dont know who has star diagnostics close to me so maybe a long slow drive in 2nd gear!

 

[C180CGI]

Try unplugging the battery terminals and reconnecting them about 2 mins later. This will clear code and car should reset its self. It SHOULD come out of gear 2 but might become stuck again after some time but is worth a try.

 

[pattiodors]

Thanks very much for the advice.
I'll try that when I get back home

 

[pattiodors]

Just an update
Tried battery unplugging, didnt work so took to my local indie in dereham who cleared codes and took for test drive, and all was fine that day, got in next day and went to tescos and all fine, went to drive home and fault is back!.
The indie said it could be they fitted new conductor plate but didnt clean contacts on solenoids, so looks like I will have to pull it out to check contacts or check continuity on the plug into gearbox,pinouts on the plug at all?

 

[pattiodors]

Another update
Had the conductor plate and solenoids removed and inspected and all is fine so now have to suspect TCU or wiring from gearbox to TCU. I have been informed that a 2nd hand TCU cannot be fitted as they are coded to the car, does anyone know if if this is so or is there is a reliable repairer for these units if I need one.
The car is w203 2004 c320 sport coupe.
Thanks for looking