How Serious is P0740?

[spciesla]

I have an '02 Jetta Auto with 137,xxx miles. Yesterday driving home from work I got a MIL. I went to Autozone after work today and read the codes with their OBD-II scanner. It read the P0740 TCC Circuit Malfunction code twice.

I haven't noticed any problems with shifting or excessive reving. In researching on the forums, there doesn't seem to be a definite answer to what is required to "fix" this code. I reset the code and will see if it comes back. One note I picked up from searching threads is to check my rpms at 75 mph (should be less than 3k).

http://forums.tdiclub.com/showthread.php?t=168981&highlight=P0740

I have had some transmission problems with my car, most recently a cracked tranny cooler at 123k (Jan 07). The tranny was serviced (filter/fluid) following the replacement of the cooler.

So, is there something I need to fix or replace? Do I just monitor the shifting and rpms and wait to see if it happens again?

Thanks,
Steve

 

[scooperhsd]

"WHEN" it happens again , use an OBDII scanner to clear it out again until it happens again - ad infinitum.

Yes - I get this ALL the time. what it means is that your transmission will not engage the Torque Convertor lockout. SO far as I have been able to tell, it just means that you are using the torque convertor all the time, and your transmission is not being as effiecient in moving the power to the drive wheels. You will see it indicating more RPMs for a given road speed and gear. I've had this same thing in excess of 40,000 miles so far, and it doesn't seem to be getting worse or better.

If you go to your VW dealer's shop - they will want to replace the transmission - $5000 new, an independent might swap in a used junkyard one (which may or may not have the same problem) for about $3000. You MIGHT be able to find someone who isn't afraid to get into the transmission and put in a replacement valve body assembly for less (and maybe some other rebuild-type work while he is in there anyway).

Your other option is to find someone who is willing to convert your 4speed automatic to a 5 speed manual.

You might check with a local TDI guru (there are a few in California) and see what they have to say.

 

[spciesla]

Have you noticed any change in your efficiency (mpg)? My mpg have dropped from approximately 41 mpg to 39 mpg since June 2006 (~ 106k miles).

 

[NETHED]

Unfortunatly, these cars have bad automatic transmissions. I have one, I'm treating it w/ very kindly to save it as long as possible.

Try changing your AT fluid, but be warned, you NEED a VAG-COM to properly fill it.

 

[spciesla]

I had the AT fluid changed in January 2007, about 15,000 miles ago at the dealership when the replaced the transmission cooler. Do you really think it needs to be changed again so soon?

 

[NETHED]

Well, since a dealer did it, I would find someone to check it. It may be low on fluid, or overfilled. I would hope they used the correct fluid.

 

[oilhammer]

Unfortunatly, these cars have bad automatic transmissions. I have one, I'm treating it w/ very kindly to save it as long as possible.

Try changing your AT fluid, but be warned, you NEED a VAG-COM to properly fill it.

Yep, not much you can do but save your pennies until you need to replace the unit. I always tell people when they look at the Moroney sticker and see the slushbox as a $990 option to just add $4800 to that. The REAL price you pay to have something else besides your left foot and right hand to shift gears.

 

[spciesla]

The work was done by VW of San Juan Capistrano, which has a decent reputation, but I'll find someone to check it with vag-com. The MIL hasn't returned yet. On the freeway this morning I checked my speed and rpms. At 75 mph the rpms were 2700. At 80 mph the rpms were 2900, seems like a big jump for a small change in speed. However, the section of freeway that I drive isn't too flat.

 

[scooperhsd]

On my car - I only get a quick flash of the MIL light for this. The transmission gets a little "clunky" in changing gears, and it "hunts" between 3 and 4 on hilly areas. When it starts hunting, I lock it into 3rd. When you see the RPMs higher than usual - go reset the code again. After it hits twice, the TCC will not engage at all.

I'm also driving gently with it. Ironically - it's driving in city stop and go traffic that seems to make it happen the most. I've gotten into the habit of just using 3rd whenever I'm driving below 45MPH - seems to help.

The car hasn't stranded me yet (at least for tranny related problems), and a quick reset with the OBDII reader (and occaisionally doing the reset to the transmission) makes everything right for awhile.