Limp mode in summer

[vanuatoo]

2003 4wd SE with 4 speed auto

Car runs great, has about 132,000 miles. This symptom developed about 10,000 miles ago.

Only in summer, when I'm on highway and it's very hot, usually with air conditioner on, car goes into limp mode, after driving around 60 miles.

The car continues to drive but it's in the 2nd or 3rd gear I guess.

Then I stop it, shut off. Wait around 2-5 minutes. Turn on and car drives normally.

 

Tranny has been serviced at 30,000 mile intervals, only putting Nissan Matic D, with drain and refill approach. Transmission filter has never been changed, as service manager told me it's just a metal screen and no maintenance is needed, just fluid change.

 

Engine valve covers are leaking badly, don't know if this can cause this problem.

Rear main seal also has some seepage, but nothing significant.

 

Any ideas?

[Slartibartfast]

I doubt the oil leaks are related. Any codes? If you can't get transmission codes through the OBDII, there is a workaround using the old blinky-lights OBD. The diagnostics for that start on AT-48 in the '03 manual. I don't know if they're like the WD21 where they only store the code for one drive cycle, hopefully not. The "judgement flicker" setup is a bit of a PITA, might be worth a try, though. Once you know what it's upset about, you can track down why.

 

Any issues with the engine temp?

[vanuatoo]

I don't have any codes. I have OBD reader, but it's pretty basic and can't read AT codes.

Engine temp is fine, at least the gauge says so. I have a custom shield underneath the engine, but it's been there for years. The only case when transmission went into limp mode, was in around 13 years ago, when I tried to quick launch from the stop light in summer.

 

As an option, I can visit the dealer and read AT codes, through Consult tool, if it makes sense and try to go from there.

Edited November 7, 2023 by vanuatoo

[jbh_CO]

Mine used to do this occasionally under the same circumstances, especially when driving it hard. I finally figured out that it was due to the transmission fluid being slightly overfilled and maybe frothing and overheating? I drained a bit of fluid from the cooler line and that took care of it for many years.

The only occurrence since then was at the top of Vail Pass at 10,666 ft with the pedal to the floor trying to maintain the speed limit (low octane gas, ethanol and altitude have conspired to rob me of a lot of HP). I had to pull over into the emergency truck lane but it was fine after I turned it off and back on. I didn't even wait more than a few seconds. It was embarrassing (and terrifying) having all the big rigs blow right past me and the family at 80 mph though.

(This was also in the summer after driving hard for a few hours in 90+ degree heat)

Sent from my SM-G998U using Tapatalk

[Slartibartfast]

Overfilled fluid could do it. The fluid level rises as the transmission warms up, so if the fluid's on the high side normally, a little extra heat could get it high enough to get air whipped into it and make the hydraulics act funny, which makes the computer think the sky is falling. Make sure you check it with the transmission warmed up, otherwise it'll read wrong. I overfilled mine by about a quart by believing the dipstick when it was cold.

[vanuatoo]

I drove from work to my home around 7 miles, it took 21 minutes. Stop and go traffic + some light highway.

Checked the level as indicated in the instructions. On the HOT side it's within the dashed zone, slightly above minimum (about fifth of the whole zone).

So level is OK.

 

I remember when I was investigating this problem, I encountered one post, when a person was talking about some clogged small filter. Don't remember where it was located and can't find that post as well.

[Slartibartfast]

The filter's not ringing any bells for me, but the AT section of the manual should show it somewhere if it's supposed to be serviceable.

[vanuatoo]

Nothing on the filter in the manual

[Slartibartfast]

Is there a screen on a solenoid, maybe? I haven't had a solenoid out of one of these, but IIRC the solenoids in my friend's 4L60E had screens to keep junk out of them.

 

I would write down the instructions for the blinky-lights OBD and keep that in the truck so it's handy the next time it acts up. Figuring out what it's actually upset about could save a lot of guesswork.

[vanuatoo]

Bringing up old thread. There is a Nissan dealer with Nissan Consult diagnostics tool. Is it worth to pay the money and use it for extracting the code which was set (if it's still there) during transmission going into limp mode?

[Slartibartfast]

If you can't pull codes by any other method, it might be worth a shot--but if it hasn't acted up in a while, who knows if the code will still be there.