Intermittent speedo drop

[Strato_54]

For the longest time now I've been fighting an issue where below 30-40kmph my speedo will sometimes just stop working. I'll start my car in the morning, start driving with no working speedo to get out to the main road, once I get to mid 3rd it will wake up. Sometimes it will just fall once I go below 50 but usually it will stay working. It definetly is not bump related as its consistant with stopping in that speed range. If i'm below that speed range it will just start bouncing or fall.  Sometimes I get a pending p0500 but never a full code. 

[Slartibartfast]

EL-91 of the '97 manual has troubleshooting info for the speed sensor and its wiring.

 

The speed-related intermittent thing is weird. Sounds mechanical, like maybe the gear on the sensor is missing a couple of teeth and if it stops in the wrong spot, it takes some time/vibration to catch and turn again? If all of that checks out, I'd be tempted to loosen and retighten the screws on the back of the cluster, on the off chance (assuming the R50 cluster is built like the WD21 cluster), though this doesn't sound like the usual loose connection.

 

Looks like the speed sensor is wired to the cluster, which then passes info along to the computer, for whatever that's worth. Interesting that the speedo's in and out, but the computer hasn't decided it cares enough to code yet. I guess it doesn't need that info for much (yours is manual, right?), so it may not be looking for that info often enough to notice when it's not there.

[Strato_54]

It would make sense if it sends the info to speedo then the computer because when I tried playing with the cluster screws it feels like its fixed but comes back few days later. I've had this dash apart more times than I would like to admit.

 

Yes it is a manual, and it does start to act up when it doesn't see a speed signal. The response feels weird and it will let out massive pops and a few flames through the exhaust, more than it normally does on decel (lol). I dont think its mechanical, because it will jump up, down repeatedly sometimes instead of staying on. So for that maybe the current is enough push to get passed any corrosion once its at a higher signal? I've had it throw a code only 1 time but never again after that, only goes to pending. 

 

I've tried playing with a few things, ut haven't gotten to a complete fix. Everything I touch fixes it for a few days or weeks then it comes back. I have not taken out the speed sensor yet though to check the gear, but that will be my next thing. It never used to turn off below that speed all the time, so thats why I never was pushed to check the gear. 

[Strato_54]

I got a video of what it did on my way to the beach. This is just 2nd gear, doesn’t matter what gear I’m in 

 

 

Edited September 5, 2023 by Strato_54
Forgot the link

[Slartibartfast]

That is weird. If messing with the cluster brings it back for a while, I would dig into the cluster again, maybe check/reflow a few solder joints. I wouldn't expect a damaged gear to falter and drop back out like that. I would say low signal strength on the sensor, except that messing with the cluster wouldn't have brought that back.

[EricCR]

Nissans from this vintage have really crappy solder, which cracks under vibration and temperature cycles. Years ago, when we had a late 90's Sentra at home, I had to fix the intermittent wipers, fuel gauge and interior illumination. All was caused by loose/cracked solder points. Older Nissan MAF designs are another example.

 

With my Pathy I already had to fix the clock that's above the AC vents and the fuel gauge, both things again due to bad solder.

 

I wouldn't be surprised if the speedo also fails in the same manner. I made a post detailing how to fix the fuel gauge and a brief Google search returned some results of other Nissans with partially working speedos (don't limit yourself to Pathfinder's info). I would look at the cluster's circuit board for signs of cracks. In cluster's circuit boards it's easy to follow the traces from whatever you want to fix to the components involved Focus on the ends of the resistors which I've seen is what most commonly fails. They will look like these (the ones that start with an "R"):