ok, here is the situation. the car is running perfect but the rpm gauge isnt working. Somedays it stays at 0 and doesnt move, while on other days it wont go over 2000 rpm.
I floored it to make sure it wasnt working and the rmp gauge stayed at 2000 when it should of gone to about 6 to 65 thousand. What is wrong, what do i need to do?? thanks a lot

 

I researched this subject a few months ago and posted some material on the subject. Right now the forum search engine is broken, and Jamie is working on it. When the search engine is restored I will attempt to find that "lost" information and post it here.

 

Combination Meter is what Nissan calls the instrument cluster, the assembly which includes the speedometer, tachometer, fuel gauge, temperature gauge, along with a slew of indicator and warning lights. There are three connectors on the rear face of the Combination Meter: M82, M83, and M84. M82 is situated near the speedometer and fuel gauge.

You may backprobe connector M82 at the rear of the Combination Meter. M82 is a white plastic connector with 14 positions. Viewed from the harness side, identify terminal #3 which is in the upper row, third from the left. The wire at terminal #3 is white with a green stripe. Measure the voltage between terminal #3 and ground while the engine is running. The factory service manual says the voltage should vary in direct proportion with engine RPMs, but does not provide any specific values. If the voltage you measure at this point fluctuates wildly, that indicates the defect lies "upstream", probably in the wiring between M82 and the ECM. If the voltage is steady but the tach reading is erratic, the defect lies "downstream", in the combination meter assembly and possibly the tachometer instrument itself. The delicate Flexible Printed Circuit connection in the combination meter is a potential trouble spot. Cracks and cold solder joints in the Combination Meter printed circuit board could also produce this symptom.