I drive a 2004 Audi A4 1.8T CVT and recently my MIL (check engine light) came on. I went to the Audi dealer and they ran a diagnostic and they said I needed to replace my Transmission Control Module (TCM) and it would cost $2500 to replace it.

I got a copy of the diagnostic from them and the fault reads: "18201 P1793 Output Speed Sensor 2 ciruit No signal." The funny thing is that when I borrowed my friend's OBDII reader there was no faults registered and because there is no faults registered I can't clear the MIL (Engine Check) light.

Do you think I really need to pay $2500 and replace the TCM ?


Thanks for reading and any advice you can offer is greatly appreciated.

Gary

 

You need a VAG code reader.

http://shop.ebay.com/?_from=R40&_trk...All-Categories

 

If your Module is going bad, get it replaced before you screw up or weaken the transmission.
You can reset the drive cycle and continue to drive it. Just do not drive it in limp mode.
My best suggestion is to take it another Shop....NOT the stealership!
I just had to have mine replaced and with parts, labor, ect.... I paid $1600 at Eurosports.
Find a good certified Audi shop and have them check it out.
Also, it took 2 weeks to get the Module from Germany....

 

hey im from australia and im having the same TCU problem where are you guys from? and do you know anywhere in Australia that will do it for cheap? thanks

 

I purchased an Audi repair manual from eBahn for my 2003 A4 Cabriolet when new. It has been well worth the outlay since it helps me know how to take off door panels, has location of components and repair procedures as well as technical bullentins. Because of the components location, I was able to replace the coolant sensor and would have not looked in the area where it is.

When my Transmission Control unit flashing display came on, I began to do my research (and have posted some information (and a slight rant) on this site). I am dissappointed in Audi's lack of responsibilty toward the CVT and it's electronic control unit, which obviously has flaws.

In answer to your question, if the PRND is flashing, it is the component inside the transmission (the TCU) that is flawed). Audi would like for you to return it to the dealership for replacement, of which the repair bill will shock you. After market shops seem to be around $2,500 total, with the unit at a price of anywhere from $1,100 to $1,500.

There are providers on e-bay that will repair YOUR unit for $350 to $500. A couple guarantee the component for lifetime and you will NOT have to get the dealership involved to obtain a code from Audi of Germany.

The manual I have refers to the flashing light and indicates the car can be driven for a few miles with no problem. If continued, the transmission control unit may generate signals that can interfere with the performance of the transmission. The manual indicates that problem that can occur are the transmission shifting to neutral (and you can't change it out of that) or the potential of locking up or... further the transmission being complete destroyed.

So, the short answer is address the flashing PRND. The code reader you used may only read the Engine codes and not the transmission codes...thus the flashing PRND light indicator versus the ENGINE light indicator, which may read other components.

 

Can anyone help with instructions on replacing the TCM on a 2003 A4 1.8T FWD CVT?

So far i understand the unit is located in the trani and it can be accessed by removing the trani oil pan and draining the trani fluid

Besides the obvious trani oil, do i need to get anything else like a oil pan gasket or anything else before starting this job? Anything in particular to be watching for when pulling it out?

I have a friend that is a licensed mechanic and will do this for me so I can ship the damn unit to Toronto, i found a company that fixes them for 300 and sum dollars (which is way cheaper then what the dealer wants 2K plus!)

Any help or advice is much appreciated

 

I can send the instructions from my e-bahn audi repair manual. Mine is a 3.0 liter, but I imagine the transmission process for replacing the TCM is the same.

I tried to send it via this e-mail, but the size is bigger than the forum allows.

Hope that helps. Richard

 

Thanks Ritchie that would be great! Can you email it to me please at kayakm71@hotmail.com

hopefully they are in the same spot and I will let you know once I read it.

Much appreciated brother!

 

Here is where the TCM is located, more from the tail shaft housing area than the pan. These #35's (plus gaskets, O rings and bolts) must be ordered from Audi off the cars vin#. Once installed it has to be programmed by your dealer also.

 

Thanks Jeff; the detailed trani info helps locating the TCM but I was just looking for someone that has taken it out before, with instructions on do and donts.....or Ritchards manual instructions should do it.

By the way and as mentioned in the original post, i found a way to avoid going to the dealer (sorry if you are working for one!) and i dont have to buy a new TCM. I found a company that can fix it, afterall is just a computer chip. THis company can fix your exsisting TCM thus eliminating the need to re-code it when you put it back in....and they life time guarantee it.

Now all i have to do is go to my mechanic with specific instructions how to pull the TCM out so i can ship it to get it fixed. He is pretty good but we just want to make sure we cover all the bases and the Audi forum has all the pros around.