aaronford

Here is a post I placed on another board regarding Nissan PU speedos. I thought it may be useful.

If you look into your speedo setup, you will find it is a digital unit with an analog sweep rather than a cable driven analog. To troubleshoot these is a little difficult and usually results in "swaptronics". The items in the speedo system are a sensor in tranny or transfer case, two wires from sensor to head unit(what you see), head unit, and one reference wire that goes to the ECU (sets off check engine light). Mounting screws that hold the speedo in place in the instrument cluster make the connection from the printed circuit to the head unit. Now all said, to troubleshoot:
1. Replace the Vehicle Speed sensor in the trannny/transfercase. Try it.
2. Inspect printed circuit and ensure continuity through printed circuit by testing between plastic push in connectors and speedo mounting screws with connectors installed (speedo and sensor disconnected). It may help to map this out with different colored markers. You will find that the four screws on the back are for 12v+, Ground, Ecu, and reference from sensor. The other sensor wire is connected toground via the printed circuit.
3. Shoot the wires to the sensor from the head unit for continuity with the sensor disconnected. Also run a continuity check between wires to make sure they aren't melted together.
4. Check for 12v and ground to speedo head unit
5. If all else tests good, replace head unit. Most places can get you one for about 200 dollars (they don't exist on the used market). Prices flex a little, but as all remanufactured Nissan speedos come from the same place, don't expect to find anyone selling them cheaper than anyone else.
6. Here is the kicker. Speedos from other models will work! I got a speedo from a 93 Sentra for 5 bucks and installed it in my 95 PU. You will find that if the screws that mount the back of the speedo are the same, it will fit. And if you look on the bottom of the speedo face it will say something like 60mph=1024 rpm. If the other speedo has the same markings it will read true. The only problem is you have to use the face from the new speedo if the speedos read different maximum speeds. It may require trimming and you may have to remove the needle, but this is pretty easy.
The needle may be tight but it pulls straight off. Before doing this make sure you twist the speedo in the clockwise direction till it meets the stop. Then mark this point and be sure that when you reinstall it, it twists to the same maximum as before. This can be a little tricky, but when done carefully is usually quite accurate. This is a neat liitle mod to do for a tricked out ride. The downside is that you now have a TMU(True Miles Unknown) vehicle. This kills resale value. I think I have the only Nissan Pickup anywhere that reads true all the way to 130 mph. Never been that fast, but now I will know when I have!!! Good Luck Aaron Ford

I am editting due to finding a better way to ensure the needle is correct. Instead of turning the needle to it's max, simply lift the needle over the zero peg and let it fall to rest. Then assemble the new one with the needle in the same place. Then lift the needle back over the peg. Much easier. AF

87-90 speedometers are indeed cable-driven, NOT electronic, just so you know. I don't know the cut-off year for the electronic speedo setup, but it's likely that it may have been as late as 1992. Thanks. -88pathoffroad