I have this problem as well, even with a brand new transmission and shift assembly with 7k or so on them, cleaned all my grounds as well (gonna check fluid soon). I have suspicions that it's temperature related; I'll have more luck downshifting driving aggressively at high speeds than puttering around town, most likely due to increased air flow (car also seems more compliant with downshifting when the transmission is cold/cooler).

Hopefully this summer I can install a larger transmission radiator, that should give a more definitive answer if temperature is the problem.

Also, your transmission shouldn't be shifting from 4th to 1st, it should hit 3rd before making the skip shift at about 26mph (possible higher if slowing down more quickly).

For you though, check your grounds (main ones are three on the timing chain cover and one below the coolant reservoir, I think there is one in the battery compartment as well), check your fluid levels, and check if something is messed up in the shift assembly (remove shift ****, remove shift cover, check the wires/switches). Worst case scenario is that something in the valve body is going kaput, which is what tipped me off when my transmission ate itself.

Sometimes this transmission just doesn't want to play nicely.

 

 

Update for anyone who opens this: Never solved the problem. Tried cleaning grounds, replacing the little buttons in the shift assembly, changed the fluid and tried resetting the ecu. Currently swapping out my auto for a MT because the AT annoys me so much.

 

Out of curiosity, are there any problems with your gauge cluster like wrong fuel level, inoperative blinker lights, dim backlighting? IIRC manumatic mode sends the signal to the cluster before the transmission. Something could be broken there.

 

I have all 3 of those problems.

 

I'd be suspicious of the cluster then. Some resistors burn/pop and cause the gauges to read wonky or not work.
There are a few places on Ebay and such that can rebuild the instrument cluster.

 

Same here. I never got mine to work right. I even had my transmission rebuilt and my manumatic is still intermittent. Maybe it is the cluster. I might change that out soon. I’ll update with results when I do.

 

The manumatic switch connects to the instrument cluster, the cluster tells the TCM the information via CANBUS. You can disconnect the MM switch, disconnect the instrument cluster harness, then ring out all the wires to make sure they're intact (also works for testing the switches to see if they actually open/close).

However with as finicky as the ground systems are on these cars I would check those first, M30 ground above the ignition key lock cylinder, also M66 behind the glove box. A grounding kit is going to be practically MANDATORY for these cars after another decade of corrosion. At least from the battery-engine-transmission-M30-M60

The instrument cluster is prone to other failures so I wouldn't be surprised if that was the culprit.

 

Nissan quality 😒

 

When my dash finally dies I'm going to tear it all apart, make a write-up DIY with how to fix EVERYTHING on it.

I'm no stranger to ripping apart PCB's, as long as the problem is just resistors/transistors/etc and not something like the CPU (doubt that's the issue) then it should be 100% repairable. I'm also going to figure out WHY these things happen but I'm already 100% convinced that it's just a poor job soldering components like the cruise control light which flickers/dims on it's own depending on the weather.

 

Is it just me, or does it seem like the majority of cluster issues are with the 2005+ cars?
My 2005 had both the erratic manual mode functionality issues and gas gauge not reading correctly. My 2004 has neither of the issues to date (knock on wood). When I browse craigslist and FB marketplace for G/Z's, it seems like its always the 05+ cars that report such issues.

 

Now Im kinda hoping your dash dies lol. It seems like every issue on these cars have been figured out except for the manumatic.

 

Thing is, I have a 6MT :P. I'll ask around and see if I know anyone with a bad 5AT manumatic code that they're sure is not the switch and see if they'll give it to me, for science...

 

Are there specific AT and MT clusters? Someone told me at one point to switch the cluster to a MT to get rid of the “CHECK AT” light. Either way my fuel gauge doesn’t work, which kills me, so I might switch them anyways. If I do, I’ll happily send you my old one.