96 Altima engine control problem?

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I have an intermittent problem with my Nissan Altima '96 GXE 2.4L A/T 153K miles:

After driving for a few minutes, I loose power with the engine above 2000 RPM (exactly). Below 2000 RPM, engine / transmission behaves normal, even at speeds of 40MPH (under light load/low RPM). Attempting to increase RPM to above 2000, causes engine speed to oscillate at 2000 RPM (Freq=~2/sec). This occurs at any vehicle speed including park.

I believe it is some kind of engine control issue, since when I turn off the car and let it sit for 15 seconds, the problem dissappears. I have replaced the fuel filter to rule this out as a cause, but did not believe that this was the culprit due to the precise way this failure occurs, and the ability to return the car to normal operation with a simple 15 second rest.

The first 6 times this happened, MIL light did not turn on, and no OBD-II codes were registered.
This morning, the problem did not occur, but the "check engine" light turned on, and 3 OBD-II codes were recorded:
P1900 "Manufacurer Contrl. Transmission" (SIC)
P0733 "Gear 3 Ratio Incorrect"
P1900 "Manufacurer Contrl. Transmission" (SIC)

Looking at sites with OBD-II codes for Nissan, P1900 appears as "Cooling Fan", so this is somewhat confusing.

Extensive searching on the web has turned up no pointers other than possibly TSB: 97-028 :
MIL ON - DTC P0731,P0732,P0733 (A/T Signals) No Symptoms. (although I'd have to admit, I do have a few symptoms -- although not when the MIL came on). I'm not able to locate the full text of the TSB.

Any assistance would be greatly appreciated!

posted by  mjassows

get some freeze spray and spray some of the ic in the ignition circuit.(especially since the problem goes away after 15 seconds.)the only other thing is removed from what one would think.,if the catalytic coverter is plugging up when heating....,it will cool off after 15 seconds,?
a bad catalyic converter will trigger up to 5 other circuits,and let people chase the problem....you have over 200000 km on your car..its very likely.the other thing is the asd circuit.this is the shutdown if you exceed the rpm.i would look at all wiring relays and connectors.i would also pull out the MAP SENSOR and check it.call a nissan store and ask if it is a common problem.looking at the 1900 code info,fan circuit.coulde it be that your cooling fan is shorted or defective?it could pull the voltage down to a common circuit.disconnect the fan connect and see if the car runs ok.maybe the rpm limiter is a safegaurd to not producing too much heat,because of a fan failure.it could even be the thermal sensor for the fan....
good luck

posted by  the lobster

These codes sound like tranny codes to me. Maybe some with more knowledge of Nissan trannys will chime in here.

posted by  tbaxleyjr

WHAT I AM THINKING IS THATthe transmission is so confused,it is spitting out codes?but this guy says its a fan code.call nissan and see what the code book says...fan or tranny

posted by  the lobster

P0733 is a tranny code - incorrect gear ratio in third

I stand corrected - P1900 is a Nissan specific cooling system code -check fluid livels and then check fan system for operation. What usually happens on a Nissan (at least on the 1995-1996 and Laters) is the temp sensor sends via a variable voltage input to the ECM which inturn operates the fan relays then the fans. Another input to fan operation via the ECM is the AC relay.

Either the relays are not working, the fans not working or don't have power or there is wiring damage somewhere between these components.

posted by  tbaxleyjr

these wiring things can drive people nuts.i have seen my share of wiring stuff when i was an electronics tech for 13 years.i am doing something different now,but i have been tinkering with cars for 20 years .here is how weird things can be:i saw a car in a chrysler service department once,it was there for three weeks,and 3 technicians were trying to fix the no start condition.one of the service advisors knew that i liked to mess with electronics. i gave a visual look at the ECM .1100 dollar box for this 1995 colt,made by mitsubishi.,it looked ok i measured the diodes transistors,took my capacitor meter and all the electrolytics were ok.BUT THE OBD2 COMPUTER SAID THE ECM WAS NO GOOD.I got the 5 pages of schematic,and the next day,asked the tech to check out a couple of voltages for me .a 5 volt rail was at 2.2 volts.the problem was a short in the opto isolator inside the distributor.we got a used distributor,and boom...the car ran..and i will tell you...after that,realized that
all cars are just big servo circuits,that rely on alot of sensor input..if the fan circuit shares anything in common with the transmission controller,it can be misled.here is a stranger one.JVC built an 80 watt digital reciever about 15 years ago.it used an stk4042 output ic.comes in with 14 vdc on the speakers,so the protect kicks in and the relay does not release ,so there is no sound.you know what they did? they took the 14 volt- and + power supply and ran the 14 volts through the dial indicator lamp.when the bulb burns out the pre amp sends -14 vdc into the direct coupled amps. i saw so many techs change the output ic and the problem would still be there and now the repair is more than quoted. so they give it back to the customer , it would come to me and i would fix it.a light bulb....and i know there is alot of kinky stuff in the car biz too...i have cought some mistakes myself.had the wheel nuts on my car (80-105 ft lbs) at 245 .can you believe it?

posted by  the lobster

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