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Re:2012 Nissan Versa CVT unusual speed sensor data
Recently bought car with the following codes P0500 P1720 P1715 P1574 all relating to speed sensors in the transmission, not ABS. Brought up live data on my scanner and one reading shows 18 mph at any speed below 18 mph, even when stopped. Can this possibly be right?
Those codes all appear to be related to a mismatch between the "regular" VSS signal, from the TCM over CAN, and another generated by the ABS module and transmitted to the ECM via the cluster over CAN. I'd scan the entire vehicle to see if there are any related looking, or U, codes. If that doesn't turn anything up then start looking at PIDs in the ABS and TCM modules.
There is definitely one that reads something like that at a standstill. I've seen it before and again recently on a 2018 sentra. I questioned it and saw in the manual it said approximate vehicle speed was the expected value. Our main cvt guy said he's seen it and thinks it's normal, but there's obviously something going on with those codes.
I've got a '14 versa I can check on, not sure if it's the same transmission though, about that one not reading 0mph.
Common wire issues with those are seen after a replacement having to do with that round one not being plugged in all the way. it twists and is weird. There is a special tool for it (that I've never seen be used) but I just put channel locks on it and make sure it's seated. Also there is a sensor on the back and one on the side that easily gets busted off or broken if you're not careful.
Full disclosure, I am not a cvt guy. I've replaced a bunch and know what the death codes look like, but have never rebuilt one or been to any of the Nissan classes yet.
The problem occurred when I was driving the car for the first time after putting in a transmission from a parts car. Drove 30 miles on the highway and it drove great. On the drive back I had the cruise on at 55 mph when it disengaged by itself. Then the CRUISE light was flashing. A few minutes later if felt like someone slammed the shifter into low as the rpms went to like 6500. I pulled over and shut it off. Turned it on and it was back to normal. Got off the highway and a mile from home it went into a limp mode. Wouldn’t go over 1800 rpm even if I did a restart. Managed to make it home where I pulled the codes as shown. Erased them and car drives fine again but need to find the cause before it happens again. Should I keep driving while monitoring those 3 sensors outputs?
I suggest you to keep an eye not only in sensors but in pressure lines (main, drive pulley and driven pulley). Those codes could be caused not only because of a bad sensor, but because the sensor itself is not detecting "desired speed".
Not an expert at CVT, but I have been playing around a Honda one (trying to program by myself with my own TCM).
When you replaced it did you do all of the relearns and fill it with fluid carefully following the manual? You would usually see pressure codes if the level isn't right, but it's good to know the level is right. These things do not run right if you don't do the learning procedure. There is a bulletin that walks you through the whole process.
If I am right, those transmissions can monitor only main pressure line. I mentioned drive/driven pulley because if you loose pressure in any of those lines (which are not monitored), chain instantly loose friction with pulleys.
Disconnected and reconnected two of the three accessible speed sensor connectors and have been driving it around town this weekend off and on. Drives great. Full scan shows no codes in any modules. The original issue only happened after driving an hour on the highway so I wasn't expecting anything anyway yet.
I did set the fluid level by the book, at the correct temperature and letting the fluid dribble out while running. Scan tool says the G sensor is calibrated and not sure about the relearns. Remember doing something like that with the scan tool but I'd think it would throw a code for that if there was a functional issue related to it.
Going to drive on the highway next and see what happens. What should I be monitoring?
I actually don't remember ever doing a 2012, but there are a few additional steps the manual going over after replacing the cvt. I don't know that it would necessarily throw codes if it's not done, but it does say a few times not to drive it until it is.
Do those codes set immediately or do you have to drive it for them to show up?
Was it a new/reman or used unit? Did you replace the TCM too? Do you have access to service info that explains erasing the learn characteristics and other stuff? Do you remember ding weird things like holding the throttle 1/4, pushing the brake, ad putting the car in reverse?
It was used from my parts car. Same year and transmission model number so I kept the existing TCM. I have the factory service manual. No I didn't do any of those things. If this was a relearn issue, why does it run just fine until that incident and all the codes are speed sensor related in the ECM. Wouldn't I see some codes in the transmission module? I do have the TCM from the car the transmission came from and could swap it in if needed. I can check what functions are available on my scan tool for erasing the memory. I did see something about CVT deterioration in that menu somewhere. I'm hesitant to erase stuff and possibly make the car undriveable.
I'm not sure, but I would definitely do all of the steps to start. It says do not start the vehicle without doing it. They aren't just scan tool steps though, so you'll want to read all of the steps. I know on the 2013 there is some learning that has to be done twice in a row and it will not work right if you don't. My 2014 note wouldn't take the second round of aux gearbox clutch point learning and it was not right until I tried it again. It may not be the cause of your issue, but you at least want to make sure it was all installed properly with these steps done. You know, you have to start with the known issues first before attempting more diagnosis. I would not drive it until this is done. It's free anyway, and only takes a few minutes. In the manual under removal and installation, at the top of the section should be a heading that says something like additional work required when replacing tcm, valve body, or cvt assembly. The degregation number is a calculation of the condition of the fluid. You are more interested in the characteristic one.
Not sure what the outcome of this is but the 2012 Versa CVT's are an odd duck. NOTHING in the MY13 or any other year apply. Follow what the service manual states to the T. I do not think any of the later TSB's apply to the 2012's. Assuming this is the then NEW Versa Sedan 2012 model.
Just an update since my last post. When I changed the fluid I also removed the round external filter which I had replaced before putting the transmission in the car, just to check if it had any bits inside after 50 or 60 miles of driving. It didn't, looked good as new, so put it back in.
It's in a canister with a thin o-ring to seal it. Apparently the o-ring got distorted on installation, 15 miles after taking it for a test drive on the highway it stated acting up again and eventually wouldn't move. Large puddle of trans fluid under the car. Fluid leaking from filter housing. Towed it back. Got a new o-ring and was careful to put the filter housing back straight and square and refilled with fluid. Also had to degrease the underside of the car from all the fluid that sprayed back there.
Went for an extended drive yesterday. 55 miles out and 55 mile back. Ran fine. No stored codes. Hoping it was just the connectors at the sensors that I cleaned up was the problem. Will drive some more and see.
