Hello everyone. I have scoured the boards, google, and the far reaches of the interwebs with no luck, and lets be honest, I haven't tried that hard but i'm at my wits end hoping that I'm not replacing this transmission. I have a 2005 TL 5AT. I have over 204k on the car and the transmission seemed like it was slipping the other day. I have no codes and no flashing D light. I noticed that if I shut the car off and wait 5 minutes, that I could go back to driving for a short time before it would slip again. My slipping symptoms are showing 3rd gear on the sportshift mode and high revving with a gradual slowdown. Occasionally it grabs and pulls forward, but eventually I come to a complete stop and can't use D, L, or R. When I test the shift solenoid valves, they all test fine. The A/T clutch pressure control solenoid valves all operate normally per my AUTEL scanner, but when I test them with my AUTEL scanner, they don't appear to test normal when driven by 1.0 Amps and I can't even test my A/T clutch pressure control solenoid valve C because it doesn't sense that I'm pressing the brake. With that said, it seems like I might have a bad pressure control valve C right? All it really does is control the lock up mechanism. Again, I have no codes so, I'm at a loss. I've seen some folks say they replaced their 3rd and 4th pressure switches but when looking at my live data on the scanner, it shows they are operating correctly and at the correct time. Am I missing something here? Could a clogged filter be causing this issues? Could I have a bad PCM? Why else would I have no codes and no flashing light like it seems everyone else has gotten?

 

Howdy - sorry to hear about your TL's transmission issues
My newly acquired '04 TL is at 202k miles, and the transmission behaves strangely at times. It had a shudder in 3rd gear, I replaced the pressure switch for 3rd gear & that issue went away. I have drained & filled the ATF I believe 4 times with Valvoline MaxLife. Both of these by themselves made the transmission shift much much faster/smoother overall.
If you can narrow down that the slip is in 3rd gear, then I would start with the pressure switch as well as drain/fill the ATF at least 3 times. Also, I would check you chassis & engine/transmission ground straps.
You can find the genuine Honda pressure switches on Amazon:
I purchased the above parts, and I'm 99% certain they're OEM & not a counterfeit.

However, one issue that I have is the torque converter lock up is often a bit weird, and occasionally there is a shudder, usually around 40-55mph under low load. I just replaced the transmission filter (located in the small housing on the top side of the transmission) and already the shifts are better than before. The TCC lockup is better but still not perfect. One thing noteworthy, is that the old filter literally disintegrated after I removed it. I was bending the pleats to get a look if any metal was in the filter media, and the darn thing basically fell apart in my hands.

 

So I have done the 3x3 Drain and Fill. I replaced the Filter. I replaced the 3rd and 4th pressure switches. I added Lucas Transmission Fix and I changed the Clutch Pressure Solenoid Valve C. The car shifts a hundred times better, but it still does the same thing. It slips and still gives me no codes and no blinking drive lights. The really strange part is that I can come to a stop and shut the car off, then put it back to ACC II and shift through the gears a few times, then crank the car in N and it will shift into gear just fine. I'll drive for a bit and it'll start slipping again. I know that the problem is my transmission needs replacement, but I can't believe it would slip like it does and that the fix is shutting the car off and running back through the gears and starting again. I would think the clutch slippage would be consistent. I pass the stall test, unless I sit there long enough and then it will fail the stall test.