# 95 Nissan check engine light, vehicle speed sensor?



## zootal (Sep 27, 2007)

95 Nissan PU

Two months ago the check engine light comes on, ECU says egr valve. I replace EGR valve, light goes off. This may be totally unrelated to the current problem, but the symptoms are *identical*.

The check engine light comes on when the vehicle is cold ONLY when I have been driving at a constant speed for a about a minute. If I'm doing stop and go driving, it will not come on. Once I hit an open stretch of city street, or the highway, it comes on. After a few minutes it goes off and stays off, usually until the next day. If I do a lot of city driving until things warms up, it never comes on at all. And on warm days it never comes on at all. On cold days it stays on longer, but still goes off after 10-15 minutes, and stays off until the next day.

This pattern is EXACTLY what it did when the EGR valve was bad.

So I check the ECU, and this time the code is 14, vehicle speed sensor. Yet the speedo and odometer work fine, and everything else works fine. And it goes off after 10-15 minutes of driving and stays off until the next day. Before I spend $125 or so on a replacement sensor, does anyone here recognize these symptoms, and does this really sound like a bad speed sensor? Yes, yes, that is what the computer is saying, but how it comes on and then goes off after a few minutes and stays off until the next day is identical to what it was doing when the EGR valve was bad.


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## zootal (Sep 27, 2007)

I reset the computer, took it on the road, and the light came on this morning for maybe 30 seconds, then went off. Checked the ECU when I got home tonight, same code, 14 - vehicle speed sensor. OK, fine, I'll quit arguing with the computer and pull it out of the tranny and examine it.

I see that there are replacements available, but none of them come with a gear. Is there a gear that should go with this? I have not yet found anyone that actually lists the gear for this thing, all I see is the sensor with a shaft sticking out that does not have a gear attached. I foresee pulling it out, finding a partially destroyed gear, and where would you then get one from?

Anyone pulled the sensor on a 1995 Nissan PU and know if it has a separate gear?


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## jp2code (Jun 2, 2011)

The CEL is generally for emissions stuff, not codes. That's because the emissions stuff is legal. I don't know how the VSS could impact emissions. Usually for a CEL, I'd suspect a dirty MAF or old, worn out O2 sensors. The connector that connects to my truck's MAF has loose wiring inside. Sometimes I can hit a bump just right and cause the CEL to come on, but that also puts my truck in limp mode really quick (hard to rev engine over 2500 RPM). You did not say if you are in limp mode.

Gear just seats on there with a little screw. Easy replacement.


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## zootal (Sep 27, 2007)

OK, guys, help me out here please....I replaced the vehicle speed sensor (VSS) because the ECU code was red-1, green-4, which is code 14 Vehicle Speed Sensor. I replaced the VSS, the wiring looks good. Take it out on the road and the [email protected]#$% check engine light comes on again. After 5-10 minutes of driving it goes off, and stays off until the next day. I get home, check the ECU and it's flashing 14 again, just like before. Nothing has changed. Where do you go from here? The symptoms are identical. Whatever is wrong, it is NOT the VSS even though that is what the ECU is telling me. What else could cause this?

(1995 Nissan PU 2wd 4cyl short bed)

Edit: The vehicle does not go into limp mode, and the speedometer works fine. It drives fine and everything works fine. Except for the CEL coming on for 5-10 minutes when it is cold, and insisting it is the VSS.


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## zootal (Sep 27, 2007)

So if I take a step back, ignore what the ECU is saying and think about it, my first guess would be a bad O2 sensor and/or EGR valve. After 5-10 minutes, it warms up and works well enough for the ECU to think it is good. The next day it is cold, and fails egr cycling diags until it warms up again.

Here is some history. Several months ago, the CEL started doing the EXACT same thing. It would come on when cold, go off after warming up, and stay off until the next day. I checked the ECU, and it sad bad EGR system. So I replaced the EGR valve, CEL goes off and stays off. Fast forward a few months, and it starts doing it again with identical symptoms, except the code coming from the ECU is now bad VSS (which I already replaced).

Is it possible that the ECU is just flashing the wrong code and I need to look somewhere else? How reliable are ECU codes, and what are the chances of this still being an O2 sensor or EGR problem, even though the ECU is flashing bad VSS?


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## jp2code (Jun 2, 2011)

Do you have the Service Manual? If not, you can download it here:










Sorry, but this site will not let me post the link to the site. It will block their address and replace it with asterisks. So, you will have to manually type it in from the picture above.

Once you are there, go to the EC section (Engine and Emission Control) and go to page *EF & EC-65*. There is a Diagnostic Procedure there for Code 14.


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## zootal (Sep 27, 2007)

That as awesome, I can't think you enough! It even has a wiring diagram. I'll run through it and post my results here.


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## smj999smj (Jan 1, 2006)

Most common cause of a P0500-VSS code in mid-90's Nissan vehicles is not the speed sensor, but the speedometer head. This is most common in Nissan trucks and Sentras, but also can occur in Altimas and Maximas, as well. There are four screws that screw in the the back of the speedometer head from the back of the cluster, sandwiching the printed circuit between them and also serves as the electrical connection between the VSS circuit and the speedometer head. Small cracks will develop in the threads on the back of the speedo head, which causes the screws to loosen and create a poor connection, trigger the P0500 trouble code and can also affect the speedometer/odometer operation, as well, in some cases. Sometimes you can do a temporary fix by tightening those screws, but there is no guarantee how long it will last.


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## zootal (Sep 27, 2007)

I pulled the instrument cluster, and verified the wiring into the ECU was good, and it is. The circuit comes from one of the screws on the back of the speedo, out through the connector all the way into the ECU, that is where the signal into the ECU comes from. I loosened and snugged the screws down, as they were quite loose, but nothing changed.

It looks like the only thing left to do is replace the speedo head, or should I replace the entire instrument cluster? If that doesn't do it, the only thing left would be the ECU itself.

Any chance this is a false VSS indication caused by something else?


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## zootal (Sep 27, 2007)

smj999smj said:


> Most common cause of a P0500-VSS code in mid-90's Nissan vehicles is not the speed sensor, but the speedometer head. This is most common in Nissan trucks and Sentras, but also can occur in Altimas and Maximas, as well. There are four screws that screw in the the back of the speedometer head from the back of the cluster, sandwiching the printed circuit between them and also serves as the electrical connection between the VSS circuit and the speedometer head. Small cracks will develop in the threads on the back of the speedo head, which causes the screws to loosen and create a poor connection, trigger the P0500 trouble code and can also affect the speedometer/odometer operation, as well, in some cases. Sometimes you can do a temporary fix by tightening those screws, but there is no guarantee how long it will last.


Looks like that is most likely to be the problem. Do you recommend replacing the speedo head or the entire instrument cluster? Any recommendations on where I could get a replacement?


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## jp2code (Jun 2, 2011)

The entire cluster is easy to swap - if you can find them! Junkyards won't sell just the speedometer; you'd have to buy that new from Nissan.


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## zootal (Sep 27, 2007)

Yeah, just four screws I think. Looks like there are a couple on eBay right now. I saw a few listed as "speedometer", so I wasn't sure if they pulled the head out which would be really stupid you would think, but there are people that strip it and try to sell individual pieces....phhtttt. So I'm talking to a guy right now, $50 for a cluster from a wrecked truck....

On the bright side, the truck just today passed emissions, so the urgency to fix this has just been put off for two years . 

I wonder what a new speedo head would cost? I hate buying stuff like this from a junk yard because the truck is 22 years old and sometimes you end up buying someone else's problems, as if I didn't have enough of my own....


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## jp2code (Jun 2, 2011)

You can get a cluster for a Pathfinder, too.

The Pathfinder instrument clusters come with fancy options like digital clock.

Hang onto the old one of yours. Parts are getting scarce.


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## smj999smj (Jan 1, 2006)

New speedometer heads used to run around $250-300, but, Nissan discontinued them, so finding a new one is going to be tough. There were several different speedometers available each year of the Hardbody. The calibration of the speedometer was dependent on the tire size for that vehicle, so, getting a used one could result in speedometer error if one doesn't get the correct part #. There are companies that repair speedometers, but, I have no experience in using them for this particular issue. It might be something to check into.


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## zootal (Sep 27, 2007)

The failure is probably in the electronics. The signal from the speed sensor/speedo is not making it out of the back of the speedo head. It's an electronic speedo. I might pull it and take a look at it, but I don't really have the equipment to make repairs on something like that, and the various components are sealed units that you can't get into anyhow. The fact that the light goes off when it warms up could be something as simple as a cold solder joint.

Looks like eBay is going to be my friend, and cross my fingers that I'm not buying someone else's problems....


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## jp2code (Jun 2, 2011)

> The signal from the speed sensor/speedo is not making it out of the back of the speedo head. It's an electronic speedo.

Could be you just need the new Speedometer Sensor that plugs in at the transmission.

Beck Arnley Speed Sensor New for Nissan Pathfinder Frontier D21 090-5015 | eBay

You should be able to hook up your Speedometer Sensor to a Voltmeter and see the voltage move when you turn the gear with your hand.

If you cannot, you need a new sensor.


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## zootal (Sep 27, 2007)

No, if the sensor was bad then the speedometer would not work. The signal goes from the sensor in the transmission into the instrument cluster. Inside the instrument cluster it goes to the speedo head, and then back out of the instrument cluster to the ECU. The signal is making it to the instrument cluster just fine, and the speedo is working. The fault here is that the signal is not making it back out of the instrument cluster. I checked the wiring from instrument cluster to ECU, and the wiring is OK. The problem is inside the instrument cluster.

Besides I replaced the sensor in the transmission, and nothing changed.


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