VUE 3.5 torque converter cycling

[m261398]

Hi there, new to the forums. Just recently bought a 2007 V6 FWD VUE, with just under 76k miles, for my daughter. The problem I’ve found is that the torque converter is intermittently unlocking and relocking every 2-3 seconds when cruising at lower speeds. It manifests by momentary blips on the tach and slight bump, the intensity of which depends on the load on the engine (barely noticeable with trailing throttle, very noticeable when lugging).

But once it gets to about 55 mph, the lock/unlock cycling stops and it stays locked like it should. I’ve verified this by putting load on the locked torque converter, but not enough to unlock it or downshift. There are no codes, and it otherwise seems to shift fine.

It seems like the PCM must be commanding the torque converter to unlock every few seconds, until it about 55 mph. Engine rpm doesn’t seem to matter, as it will cycle at a higher rpm in lower gears, and not cycle at lower rpms in 5th gear. Road speed is the determining factor. For instance, at like 52 mph, it cycles, but like at 56, it doesn’t.

Does anyone have more specific information on the logic the PCM uses for torque converter lockup? I’m sure that there are many variables such as engine rpm, transmission input and output shaft speeds, engine coolant temp, transmission temp, throttle position, shift lever position, brake light and cruise control circuits, etc. It would help to understand what it's supposed to do, in order to figure out what it's doing wrong.

I’m aware of the service bulletin to reflash the PCM, which I’ve not done. And I’ve read that the transmission fluid should be replaced more frequently, which I’ve also not done yet, but plan to. However, it sounds like those are more frequently used to remedy judder or vibrations. This feels like normal lock and unlock, just happening every few seconds. The reflash may prevent locking up at lower speeds, but that might just mask the true cause, if not the PCM at fault. If someone knows exactly what the reflash changes, I’d be curious to know. For instance, does it alter the overall lockup parameters, or just raise the minimum speed for lockups?

I think my first step is to figure out if it truly is the PCM commanding this behavior, or if it’s the transmission/torque converter. I don’t think it's the latter, since it works fine above a particular road speed. I probably need a scanner with live data to see what the PCM is doing when the symptoms occur. So I’m in the process of looking at the price of scanners, which I’m sure I’ll use again, versus the diagnostic costs for taking it somewhere. I’m hesitant to take it somewhere, only to have them guess, or just take the easy way and simply say that the torque converter must need replaced.

If anyone has any other ideas, I’d love to hear them. Thanks!

[Mr Toad]

I thought the converter locked up in 2nd gear and stayed locked through the gears. Mine will shift in and out of 5th, maybe 4th, gear at around 35 mph. Kind of annoying when the speed limit is 35. I know the week side to this Honda setup, engine and transmission, is the transmission. Mine would drop out of gear at stop signs. Had to have it rebuilt.

[m261398]

In case it's of any help to anyone with similar symptoms, I found the attached during a web search. It looks to provide some look into the the transmission logic. It's titled for a 2005 Red Line, but I'd think that any 2006 or 2007 V6, as well as 2005 non-Red Line V6 models will be very similar, if not essentially identical.

[Mr Toad]

The flow chart reminds me. Check your alternator and battery. I had a friend that had transmission problems that no one could find. Turns out the alternator wasn't working properly and the voltage would drop below the threshold for the transmission computer to work properly.

[m261398]

Update - I started changing the transmission fluid yesterday, as I was planning to do. Got just over 4 qts to drain out, and replaced it with the correct DW-1 type fluid. I have no idea if it's been changed before or, if it was, done with the correct type. The fluid was brown, though still had some reddish color looking through the stream as it was draining, and didn't smell burnt. The magnetic drain plug had the expected black sludge (metal powder), and no large slivers.

When I drove it after that, it seemed better, with the TCC cycling much less noticeable. Of course since I'm hypersensitive about it now, so I think I could detect a little of of it still happening. But it was so slight that someone not familiar with the car might not have even noticed. And as others have experienced with fluid changes, I swear it felt tighter and more responsive.

I wouldn't have expected that the fluid was related to my symptoms, as it felt like full disengagement and re-engagement, not slipping or juddering. But, I'm not going to argue with the results. I've ordered more fluid, and will drain and refill two more more times. Hopefully this is all it was.