Question about transmission issue- 2007 M45

[big_dish]

Hi Guys, I spend a ton of time on here reading and lurking for the past couple of years, but not really posting. Tons of great info and classy modification ideas, thank you everyone for contributing (wish I could contribute more but my car is bone stock right now)

Anyways..

I’ve tried searching and there doesn’t seem to be too many transmission topics (which is a good thing!)… I have a transmission issue was hoping someone could possibly give me insight into before my appointment at the Stealership tomorrow..

Today I was driving along (I'm an easy/slowish driver) and suddenly the car seemed to be stuck in what I guess would be second gear and the SES light came on. I had just taken off from a red light at a turn, and was going maybe 25 mph when I realized what was going on. As far as speed I could drive once this happened- 30 mph and around 4,000 RPM was the most I was pushing it after the issue presented itself. I pulled over into a gas station and reverse wouldnt work at all. I drove a few miles home and turned the car off in the driveway. I promptly turned it back on and reverse worked- and the car shifts into all gears now, although "seems" a little jerky but nothing too bad and could just be in my mind. All power functions in the car work. SES light is still on. The only other issue the car may have is that the rear brake pads SEEM to be worn very low (was planning on replacing this weekend). As of right now, the SES light is on, car shifts manually and automatically through all gears and reverse works again. Any ideas what could cause this? I dread the idea of the Stealership tomorrow but dont think its avoidable unless anyone can make sense of this.

Thank you in advance for any ideas and insight!!

[big_dish]

Also, my car has about 56,000 miles on the ODO, if that matters. Old granny had it before me so the transmission has likely never been pushed hard a single time.

[pedsemdoc]

Sounds like you need to go get some codes pulled to figure out what specifically might be the problem...go to an Autozone/O'Reilly's to get them to check what codes come up, if any

Do you have any other indicator lights on in the dash? VDC, RAS or SLIP lights? several guys have had problems with their crank and/or camshaft position sensors with all those lights on.

lot of possible issues - which the dealer will love charging you to hunt down that "snipe"....

good luck

Craig

[big_dish]

Thanks Craig. The way I realized my rear brake pads were low was because a few days ago I had to hit my brakes somewhat hard to make a turn into a hidden driveway, and all those lights popped on. They turned right off after restarting the car, but I poked around on this site and saw it could be a brake issue- and subsequently realized the brake pads were very thin (no grinding though). Ive taken it easy on them since then and havent seen the lights again.

One of the things that popped into my head when the transmission issue happened was "could this car be smart enough to know when the brakes are worn out, and try to limit the car"? But if that was the case, I would think it wouldnt stick it in a gear, but rather just put it into a limp mode.

I'll definitely take it up to Autozone in the AM and try to pull the code. Hopefully it isnt ridiculously general and doesnt help!

[big_dish]

Just in case I can figure this issue out and this thread helps someone in the future, here are the codes. One is my brakes, I think the other two are transmission. I am about to research them now.

c1155

P1774 (thrown several times)

P1731

[big_dish]

I'm just going to give a running update here- just in case something either resonates with someone reading it that has advice, or if I find the solution and someone reads this down the road that needs help like I do/did.

Its hard to determine exactly what the two P codes are in relationship to what exactly the issue is with the transmission. One thing I found was that my tran fluid may be low, checked it and it was. Went to Infiniti and bought trans fluid, topped it off. No noticeable difference. Car drives fine except for a hiccup in between second a third gear, kind of a slighty hard shift. SES light still on.

Unplugged positive terminal from battery when I got home to see if maybe it was a communication error in the system. Hooked it back up after about 30 minutes and SES light was off now. Drove for approx 10 minutes and the 2nd to 3rd shift issue is still there, SES light remained off. I dont know if 30 minutes was long enough to really clear out the memory and reset the communications. I will probably unplug overnight tonight. I'm hoping its not some kind of solenoid that would need a transmission tear down. I have warranty to 100k miles on all lubricated parts, and I dont think a solenoid replacement and the work that goes with it is covered. Trying all the cheap options first I guess.

[big_dish]

Did the ECU reset on here (tap dancing with the accelerator) and afterwards the car seems almost fine. Drove about 20 miles and generally shifted fine, but a couple times had a mildly choppy shift from 2nd into 3rd. No SES light.

Codes were as follows:
P1731 A/T 1ST ENGINE BRAKING - basically a failsafe to prevent massive speed loss if car goes into limp mode
P1774 Low Coast Brake Solenoid Valve Function - a solenoid within the transmission casing somewhere. Shifts gears into optimum position.

Anyone ever deal with or have to repair something like this?

I guess I will wait and see if the SES comes back on or if the transmission acts up. At this point I dont know if it was a one-off electrical/communication issue, or if something worse is in play. Car seems virtually perfect right now, so I am thinking unless it acts up, I am likely not doing any damage to anything.

If anyone wants to chime in, feel free.

[DeanM45]

More than likely running with low trans fluid caused a bit of where on the clutch packs. That "debris" made it into the solenoid (probably the #2 solenoid or line pressure solenoid). If the problem does not present itself again I would not worry about it. However, if the problem does come back it is not hard to fix.
Drop transmission pan, remove valve body, replace solenoid and bolt everything back up.

If the problem comes up again just post back and I can go into more detail about valve body removal.

[big_dish]

Thanks Dean, I think you may be right. The car seems to be shifting fine now (knock on wood).

Would that be an easy fix even for a novice? haha

I do have a transmission warranty to 100k miles, but it mainly covers lubricated parts- I'm not sure the solenoid would be considered such, even though from my understanding it is in lubricant.