my 94 pathfinder has a goofy speedometer, when I take off, the speedo jumps up to about 60 mph then drops down to around 10 mph before finally settling into the true speed I'm going, it also jumps up or down in speed while driving. what could be causing this? I'm told the speedo is not cable operated but instead uses a vehicle speed sensor, where is the sensor located? and can the sensor just bre cleaned? or do I need to spend the $75.00 plus to replace the sensor....please help
Ive read some posts elsewhere on this and it seems that the nylon speedo gear in the tranny may be at fault, is this possible? if i need to replace the speedo, would a used salvage yard one be ok?
'94 and '95 Pathfinder use a known defective chip in the speedometer head. You can try replacing the gear in the sensor but I doubt that's the problem. Gears are not usually intermittant. You can remove the old one and look at it to be certain.
Regarding the defective chip - you can't buy it because it is custom for Nissan and they don't sell it. That means you need a whole new head. You can buy one at a junk yard, but it might be bad also.
In my case, I designed a replacement circuit for the defective chip. However, I don't recommend this route unless you really know your electronics. It requires cutting traces, adding components and recalibrating against a frequency generator.
This problem really sucks because it affects your odometer, trip odometer, speedometer and cruise control. In addition, as it gets worse, it will cause your check engine light to come on with the code telling you the speed sensor is bad.
You might find that this problem only occurs when the defective IC is cold. If you bought this vehicle last summer and only seen the problem recently, it may be that the prior owner knew about it.
For additional information, go to Google Groups and search for AN8363.
That sure smells like a sticky speedo cable. My '87 PF had a speedo cable. Dunno about the later ones, but the speedo asy was really easy to get out -- a half dozen screws and a little jiggleing and out it came. Check for a speedo cable, and it hast one, pull the center part out and lube it.
That was EXACTLY when mine happened, when it was cold in the vehicle. Once the heat really had things warmed up (like if I went on a 30-45 minute trip) there was never any problem. But towards the end when I finally had enough extra money to replace it, it was failing like crazy in the cold.
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