Hello all,

I purchased a 2006 TL last week and before being able to enjoy the car I got the dreaded flashing "D" that night...after getting the code it diagnosed it is in fact the 4th gear pressure switch that failed. The dealer has ordered the part but says it will not be in until Wednesday or Thursday (2-3 days from now). My question is: is it safe to be driving on a bad pressure switch? What can potentially happen if this issue is ignored?

Any feedback is greatly appreciated!

 

Hopefully it's just your switch and not your transmission... the 04-06 TL's have pretty fragile transmissions. I'd hold off on driving it

There's also a guide here to DIY: https://acurazine.com/forums/third-g...2006-a-729149/

 

I wouldn't drive the car and I would consider yourself lucky that your car even gave you a code. I would also immediately replace the 3rd gear pressure switch as well.

Essentially the pressure switches dictate how much clutch pressure is applied during a shift.

I took this from the link:
"If [the pressure switches] drift out of spec they will affect switching from clutch pressure during a shift to line pressure in gear and can drastically cut clutch-pack clamping forces. It appears they only have to be out by a few PSI to affect clamping forces and pressure switching to clutch-packs, resulting in slippage with burnt and worn clutch packs failing quickly without the owner being aware of any problem until it's too late."
Link: AT3rdClutch

Many of the issues with the '04-'06 3G TL transmissions were due to the 3rd gear pressure switches failing. Once that pressure switch falls out of spec, it can cause the clutch packs to slip because they aren't receiving enough PSI to engage the pucks and will slip and burn up, from what I understand. That's why I am high suggesting you replace it.

Did you notice any issues with the transmission changing gears prior to the D light flashing? Issues with the pressure switches can cause flaring between shifts. You want to feel the transmission shift gears and then almost instantaneously be in the next one. Before I did the 3rd and 4th gear switches on my car, I could feel the car shift, but it would basically hang for a second before it actually engaged the next gear. You don't want that at all.

I would do a 3x3 drain and refill of your transmission fluid. Make sure it does not smell burnt, otherwise that means the car has been burning the clutch packs, which is definitely not a good thing.

Let me know if you have any other questions.

 

Thanks for all the great and detailed information! That is extremely helpful. My transmission is definitely not instantly changing gears (drive to reverse and vice versa), however past cars I've had haven't shifted instantly either so I thought nothing of it. I feel like an idiot for passing this issue off as a minor annoyance that didn't require immediate attention.

I will hopefully have the parts replaced tomorrow, I asked them to just replace both 3rd and 4th. I have checked my transmission fluid after a drive (warm) and while cold and it was light pink both times. The transmission is also very quick and smooth to while shifting from 1st-3rd gear, but I feel like acceleration is rougher after shifting to 4th (I assume because of the 4th clutch pressure switch not working). However it does NOT show any sign of slipping. Do you think this still requires a 3x3 change? Should also make mention there is 113,200 miles. I am hoping that all goes well...

Will hopefully be back to share some good news.

 

If it's light pink, I don't think you need to do 3x3. Hopefully, after you've replaced 3rd and 4th pressure switch, everything is back to normal.

 

The delay from going between Park and Reverse and Reverse and Park is unfortunately just a quirk of this transmission. If the delays are significant, than you may want to replace the transmission fluid, but a 1 second or so delay is not out of the ordinary.

As long as the gear changes are happening quickly, then you should be fine. What you do not want is the car to shift gears and then have the RPMs surge up before the car gets into the next gear. That's when the clutch packs are slipping. I had this happen yesterday when I was going from 4th to 5th at above 4k RPMs, the car shifted and then went up another 100-200 RPM before fully engaging the next gear. So now I am really paranoid.

Just make sure to keep up on doing the fluid changes. I may start doing a 1x3 change on mine every oil change. I suggest attempting to change the fluid by yourself if you can. That way you can see if there is excessive build-up on the drain plug and check to see if the fluid has any burnt smell to it. Any burnt smell means the clutch packs are slipping.

 

actually that isn't technically true they are very good transmissions however it is actually due to the faulty 3rd and 4th transmission pressure switches that give these transmissions such a bad name but as long as these are changed accordingly when they fail these transmissions will outlast the vast majority of transmissions in vehicles even to todays standards the only reason these fail early in nearly all situations is due to not changing these sensors when they fail i know this thread is old but still very useful information that can save tl owners thousands of dollars

 

What is a sign that they are failing? Hard shifts? Just curious as I am new to the car and want to know what to watch for. Thanks.

 

The PRIMARY reason they fail is because of infrequent fluid changes.

 

If you keep up with the fluid changes/levels and experience hard shifts, the switches are the next thing to look at.