04 CTT transmission stays in 6th.

[ARModen]

Here's a puzzle for someone more familiar with the transmission control system.  The ctt has 95K miles on it.  It was shifting a little rough when cold, otherwise no problems.  I drove several hours on the highway, and when I came down the off ramp near the house it didn't downshift.  Luckily I got all green lights to the house but it never downshifted out of 6th.  I tried putting it in manual to force it to change, but nothing. It went to M but wouldn't come out of 6th.  Once stopped in the driveway it shifted to 3rd.  I replaced the filter and flushed the fluid pretty well. (seriously.. check the filter o-ring twice before you put it back together.)  Now it shifts even smoother than before, which is good, however I had the same problem with it sticking.  After the oil change I drove 2 hours down the highway.  When I stopped at a toll, it refused to downshift out of 6th in manual or automatic.  I came to a complete stop to pay the toll, and then it shifted to 3rd and refused to up or downshift in auto and manual.  Luckily, there was a rest area immediately after the toll booth.  I stopped, turned the car completely off and immediately back on.  The transmission returned to 2nd and I drove another half hour in 6th gear, and around town for the last 2-3 days with no problems.  I don't get any weird smells, sounds, or shifts, and no fault codes leading up to the problem.  I have a couple of theories, but since it is so specific about what gears it will use (only 3rd and 6th) I'm thinking that there might be a very specific solution. 

[bigbuzuki]

Any codes?

I would check / reseat the connector on the transmission control unit under the right front seat.

Also note that there was an issue where transmission fluid can wick up the cable and contaminate the TCU connection.

[GSpence2]

hmm...that's curious. my issue is I get an odd display/warning in the gear selector indicators but the tranny upshifts and downshifts smoothly through all gears and it isn't throwing any codes! the car drives normally but the cluster gives this wacky warning after about 25-30 mins of driving. I've driven 60 miles like this and no problems encountered whatsoever. I had the tranny serviced at 119k before this started happening.

[bigbuzuki]

The display with the all the PRND lit up can mean your transmission is in a Limp mode. (Degraded mode).

You need to get the codes read to determine what is causing the fault.

Edited September 23, 2015 by bigbuzuki

[GSpence2]

hey big! thanks for the reply. that's the crazy thing though, it's not showing any codes particular to the instrument cluster or ECU when we scanned it! it actually happened once when I was at my independent getting some vacuum lines swapped out and he immediately connected his  scan tool and there was nothing showing other than the vacuum and intake leaks I was there for in the first place. there's no reduction in performance and I can see and feel the box upshifting and downshifting normally as I drive it. it doesn't lock up in any particular gear. I can turn it off, turn it back on and it's back to normal for another 30mins or so. I'm guessing it's electrical - something is getting hot and causing a bad connection.

[bigbuzuki]

Good that it's not the transmission hardware.

Hopefully it's an indication fault only.

[ARModen]

Yeah check your connections.  I caused that one time when I was taking the control module in the dash apart to replace the handle and some other stuff. 

 

So far I haven't seen the transmission shifting issue again.  I guess it must have been a clogging solenoid valve port.  Hopefully the thorough flush and cleaning took care of it.  I've been driving it all week since the fluid change and it hasn't happened after the very first night.  It didn't throw any transmission related codes when it happened.  It gave me some misfire codes, but probably related to me doing 10mph in 6th gear.

[GSpence2]

thanks guys!