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'97 Pathfinder A/T with an odd speedometer issue


thegenericguy
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Video demonstrating some of the problem, the noise that isn't the key turning is just the air coming on because I left the switch on. Sorry for the bad camera work but it's the best example I've been able to film.

 

https://www.youtube.com/watch?v=k6Sv_9V9uT8

 

Basically, when the key is turned to on - even if the engine isn't turning - the speedometer climbs to between 13 and 18 miles per hour. This offset is somewhat random, and this is just the top and bottom values for the range I've observed. When the car is off, it slowly falls back down to the resting position, however it does this at very inconsistent speeds and doesn't seem to always go to zero, instead sometimes resting at around 5 miles per hour and not settling any lower. It seems to fall much slower if the car has been running for a while. 

 

Under relatively normal acceleration and deceleration the speedometer will move at the correct rate up and down relative to my speed, and so it maintains this offset well enough to get an accurate reading of my speed as long as I remember it when I look. However, under rapid deceleration, the needle will move down significantly slower than the change in velocity, and will need a few seconds to catch up. Or catch down, I guess. 

 

This problem confuses me and I can't really find anyone who's had something similar or who has a guess as to what it might be. I haven't been super extensive in my efforts to fix it so far, though, which is one of the reasons I'm making this post; I really don't want to start pulling things apart and looking around without asking first, as it'd suck to pull the dash off and then realize it's an issue that didn't require that, for example. I'm inexperienced enough with auto work that my efforts to diagnose in repair are as much a liability (via making mistakes fixing or via failing to correctly reassemble things) as an asset, so I want to get as much info as I can before continuing. 

 

If anyone has relevant info on what this might be, what I should look at, and just any general info you'd think would be helpful, I'd appreciate it

 

Also, my first post here, or on an old style forum of any kind. Hi people! You all seem cool.

 

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What you've described are strange symptoms. I do know that the VSS connects directly to the IC before it gets to the computer. Does your O/D OFF light flash when your start the engine? You could theoretically unplug your VSS from the passenger side of the transfer case and see if the symptoms change. If the problem persists, that would point to an issue with your IC. If the symptoms change or the speedometer doesn't move, it could be a problem with the VSS or the wiring from the VSS to the IC.

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6 minutes ago, XPLORx4 said:

What you've described are strange symptoms. I do know that the VSS connects directly to the IC before it gets to the computer. Does your O/D OFF light flash when your start the engine? You could theoretically unplug your VSS from the passenger side of the transfer case and see if the symptoms change. If the problem persists, that would point to an issue with your IC. If the symptoms change or the speedometer doesn't move, it could be a problem with the VSS or the wiring from the VSS to the IC.

The O/D OFF is reading correctly, I live in a very hilly area and my commute requires a lot of transmission braking so I end up using it a lot more than most people would. 

 

As for the electrical stuff, I'll get back to you on that once I've tried what you suggested with unplugging the speed sensor, which'll be tomorrow as for some reason people in my house get mad at me when I start working on my car at 1:25 AM

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That is a weird one. 

 

The flashing OD light isn't a test of the OD cancel system, it's a blinky-lights transmission diagnostic system (a holdout from the first-gen trucks). There are instructions in the AT section of the service manual (download for free here) to decode the flashes, but if you have an OBDII scanner, you can just plug that in and get the same info without learning to read judgement flickers. Looking for the flashing light at startup is just a quick way to see whether the transmission computer is upset about something. You may have to check this with the OD switch on (idiot light off); I'm not sure if it can turn the light off to flash out codes. 

 

If you do have an OBDII scanner, I would be curious to check the live data and see what the computer thinks the vehicle speed is. If the live data matches reality, that suggests that the sensor is okay, and the gauge is acting up. If live data matches the incorrect gauge, either the sensor is acting up (and I'm not sure how it would generate a signal when the truck wasn't moving), or whatever's wrong in the cluster is also sending bogus info to the computer.

 

The service manual has some basic circuit checks for the speedo circuit on EL-91. Looks like it's just checking power, ground, and the wiring to the sensor. Without those things, the gauge would not be moving at all, so I'm guessing they're not the problem. Still, not a bad idea to run those checks anyway to make sure the readings are correct. A present but incorrect speed sensor signal or weak voltage could be confusing the circuitry and making it do weird things.

 

While the cluster is out, check that the screws holding the circuitry to the back of the cluster, especially the four screws behind the speedometer, are clean and tight. Those are the electrical connections for the gauges. The first-gen clusters are built similarly, and I've read you can sometimes fix a glitchy tach in those by loosening and re-tightening the screws.

 

I see in the video that the needle isn't going down to zero, even with the power off. That makes me wonder if there's something physically stopping it or binding it up. If none of the above gets you anywhere, I would take the clear plastic cover off and check that the needle moves freely. Then, either way, I'd tear the cluster down further in search of the issue. Unless there was an obvious smoking gun like a dead fly in the mechanism or a cracked solder joint, I would still end up throwing a new (used) cluster at it.

 

Good luck! Let us know what you find. 

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  • 2 weeks later...
That is a weird one. 
 
The flashing OD light isn't a test of the OD cancel system, it's a blinky-lights transmission diagnostic system (a holdout from the first-gen trucks). There are instructions in the AT section of the service manual (download for free here) to decode the flashes, but if you have an OBDII scanner, you can just plug that in and get the same info without learning to read judgement flickers. Looking for the flashing light at startup is just a quick way to see whether the transmission computer is upset about something. You may have to check this with the OD switch on (idiot light off); I'm not sure if it can turn the light off to flash out codes. 
 
If you do have an OBDII scanner, I would be curious to check the live data and see what the computer thinks the vehicle speed is. If the live data matches reality, that suggests that the sensor is okay, and the gauge is acting up. If live data matches the incorrect gauge, either the sensor is acting up (and I'm not sure how it would generate a signal when the truck wasn't moving), or whatever's wrong in the cluster is also sending bogus info to the computer.
 
The service manual has some basic circuit checks for the speedo circuit on EL-91. Looks like it's just checking power, ground, and the wiring to the sensor. Without those things, the gauge would not be moving at all, so I'm guessing they're not the problem. Still, not a bad idea to run those checks anyway to make sure the readings are correct. A present but incorrect speed sensor signal or weak voltage could be confusing the circuitry and making it do weird things.
 
While the cluster is out, check that the screws holding the circuitry to the back of the cluster, especially the four screws behind the speedometer, are clean and tight. Those are the electrical connections for the gauges. The first-gen clusters are built similarly, and I've read you can sometimes fix a glitchy tach in those by loosening and re-tightening the screws.
 
I see in the video that the needle isn't going down to zero, even with the power off. That makes me wonder if there's something physically stopping it or binding it up. If none of the above gets you anywhere, I would take the clear plastic cover off and check that the needle moves freely. Then, either way, I'd tear the cluster down further in search of the issue. Unless there was an obvious smoking gun like a dead fly in the mechanism or a cracked solder joint, I would still end up throwing a new (used) cluster at it.
 
Good luck! Let us know what you find. 

How hard would it be to put a 98 Cluster in a 97? The 98 has the digital odometer read out and the 97 has the analog? Would it be simply plug and play? I’m having the same issue with my speedometer working sometimes and others it’s not. I can reset the trip and when pushing hard on the trip reset sometimes my speedometer will start working. Really curious about switching a 98 into my 97.


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