Car is a Maxima SE 2000 with Aut. trans.

Symptoms: Car has erratic transmission operation. Car won't shift in 3rd and 4th gear. 4000rpm at 75km/h, if you push the o/d button and take it of, the transmission slips and engine rev to cutoff. Engine seams to work properly, and idle is good. Shifts from reverse, first to second gear is smooth. But will rev up or get back to first gear without behing needed or with any additionnal throttle.

What I've done so far:

-6 months ago:
Replaced the MAF sensor after an erratic throttle response episode - this was before the transmission problems started occuring. I also cleaned the throttle body at that time and replaced air filter.

-This weekend:
-I adjusted the TPS properly, to get 500ohms closed, and 4000ohms with WOT. Operation is smooth and gradual and you increase throttle.
-Took off the tranny oil pan, took off the solenoids and cleaned everything including the debris magnets at the bottom of the pan. Made the solenoids operate with current and made them "click" properly by cleaning them with compressed air. Tested - works fine. Reinstalled.
-Took out the TCM, opened it, checked for cracks, cold soldering issues and for fried components, board is perfect from the exterior, no issue. Reinstalled.
-Took a look at the crank position sensor under the engine, near the oil pan. Took harness off (was hard to get out), inside of the connector looks clean, no debris or grease. Didn't pull the sensor off tought...

I also did a scan, found the following codes:

-P0744 Torque Converter Clutch, Solenoid Circuit Intermittent
-P1446 Evap canister problem
-P0174 - too lean - bank 2 (I think this is normal as I have a small hole in the flexible part of the exhaust, just before the cat...)

I erased the codes after I had worked on the car, and went for a test drive. Car still did the exact same thing. Only the EVAp code came back (haven't check that yet).

What I suspect now:
-bad revolution sensor
-bad crack position sensor (don't know if it can affect the transmission operation like that tought...)
-TCM and/or ECM need a reflash / reprogram (considering I adjusted the TPS, changed MAF a while back etc...)

Let's hear what you guys think!

Thx!

I would find a junk yard trans and torque converter. You could get it rebuilt, but there a a ton of auto trans that will work. You will come out ahead with a JY trans $ wise. Any trans from 95-01 A32/A33 chassis will work in your I30. No reflash, no splicing, ect. Just slap it in, torque it down, fill it up, and youre back on the road.

Good luck and Happy Motoring.

Revolution sensor. P0720 is a ghost code. Ive got one right now with no CEL. When the CEL does come on it shows P0500 on most scanners but I've already replaced it. Ive seen the P0720 on a more advanced scanner and can say thats probably the culprit. Mine just hasnt become quite so erratic yet.

your trans is worn out, get it rebuilt or swap in a used one. Mileage??? one of the most important factors. you have the torque converter solenoid code, tcm detecting an open circuit, which is based off either disagreeing signals from crank sensor and output shaft sensor, a bad solenoid, bad tcm or shorted wiring. also what is the trans fluid level and are you checking it properly?

also what 02 sensor was the lean code for sensor one or 2