Y38n1 Fault code, easy and cheap cure

[microlite]

Hi everyone,

It's been years since I posted on here, I've had a bad experience in the SLK350 and I thought it would be good to share it with you.

About 15 days ago I took off from stand-still flat out in sports mode and kept the pedal to the metal until 3rd gear was selected and then lifted off. As I lifted off I heard a banging sound which seemed to be from the diff. The car went into limp mode so I pulled up and turned ignition off and back on and all seemed good.

About a mile or so later the car went into limp mode again and each time the car was reset it would drive perfectly until it happened again. I went to a local garage and the diagnoses showed fault code Y38n1. I started researching this and concluded it was the transmission control unit (TCU).

I contacted my local Mercedes dealer and was told they could not check the car until the 11th of May so I started calling independent dealers and I was told they knew what the problem was and it would cost me between £700-£900 and they also told me Mercedes would typically charge around £1700-£2000 for the same work.

I then started looking at tackling the job myself. I found a company called ecu.testing.com who described my Y38n1 fault accurately and offered to repair the TCU for £220.00 + VAT. I booked my TCU repair with them and with the help of my brother took the TCU off the car and sent it to them. The TCU was returned yesterday and the car is in perfect working order again.

The SLK is now 9 years old but with only 23000 miles on it. It is very well looked after and I couldn't understand how this could happen. I spoke to one of the tecs at the repair centre and was informed this is a very common problem on 7Gtronic transmission and if I went to Mercedes the chances are the new TCU they would have supplied would have failed again as they are poorly built. I now have a life long guarantee on my TCU.

If anyone else is having a similar problem then I hope my story will help in some way in you deciding how you should deal with it.

Take care and safe driving.

 

[Cole@MBS]

We have used said company many times before without any issues, quick turn around times and not bad costs.....

 

[Steve@Avantgarde]

Yeah they aren't bad, ACtronics also repair them. However I am finding that on most which have these faults its a build up of dirt on the sensors and pick up rings on the box. Flushing out the valve body and cleaning the pick up rings on the box with electrical cleaner and doing a full ATF change including the TC and resetting the adaptions seems to sort the issue and quite a bit cheaper than replacing the plate too.

Just did my old mans 230k mile E320CDI with the same fault.

 

[microlite]

Yeah they aren't bad, ACtronics also repair them. However I am finding that on most which have these faults its a build up of dirt on the sensors and pick up rings on the box. Flushing out the valve body and cleaning the pick up rings on the box with electrical cleaner and doing a full ATF change including the TC and resetting the adaptions seems to sort the issue and quite a bit cheaper than replacing the plate too.

Just did my old mans 230k mile E320CDI with the same fault.

I am sure this was not the case with my TCU. My sensors (8) were removed by me before dispatching the unit and in fact they warn you to mark their places to make sure each sensor goes in its correct place. I had a long look at the unit before dispatching it and a long look after receiving it and the only thing they could have replaced was the flexi-wire.

This wire is thin flat copper strips squeezed in between transparent brown kapton tape like stuff. I'am convinced this wire was replaced and nothing else. Looking at the unit there is nothing else they could have done anyway. I am vert pleased with the service and the end result. I know for a fact if I had gone with Mercedes they would have put a new unit and the flex-wire would have gone open circuit just like this one.