Speedometer stopped working?

Hello BDAB68,

Can you monitor all of the wheel speed sensors and drive in a straight line and see if there is any one of them are off? Any erratic readings?

Also, this may sound obvious but are your tire pressures all the same, and correct according to the manufacturer spec on the door jamb? Also how is your tire wear? Anything abnormal or a tire that has more tread than the other?

A worn bearing or tire as well as a bad wheel speed sensor either from age or excessive resistance in the harness could give the computer mixed information and maybe why it's doing that. Inspect each wheel speed sensor harness for any damage like blistering or it is rubbing through. Also, a tire with too much tread on it compared to the rest could cause an issue.

Just a thought. Want to rule out these things then we can move on from there.

I am adding some images of what to look for in tire wear.

Take a look and tell me what you see. I will be here.

Thank you,
Brendon

Good morning, BDAB68,

Okay. Thats good. We can rule that out. It's part of the same system. Sometimes they use both, my truck for instance uses a speed sensor on the tail shaft housing on the transfer case along with the wheel speed sensors. I just don't want to overlook something. It is important to try and be as thorough as possible and not rule out the more likely possibilities first.

So, moving on. You drove the vehicle with a scan tool on it and monitored the speed. So, the scan tool showed the speed you were moving at but the speedometer was at 0? Is that correct? Could you elaborate on that test?

So, anything else besides the speedometer, odometer, and cruise control having an issue?

I am adding some wiring diagrams and have highlighted the areas you should check.

First image is a diagram of how the power is sent to the sensors called-Joint Connector C123 (right of blower motor). I would locate this and see if there is any damage or corrosion. Since it is an intermittent issue sometimes shaking the harness can get it to work or act up. Figure one shows you the location of the blower motor. These wires should be orange and send power directly to both A/T Pulse generators or VSS.

Second, there is a white wire coming from each sensor going into the PCM (Under the left side of dash). Number 20 and 28. I have faded out other wires and highlighted the ones I am talking about to make it easier to see. Check these wires for any damage or rubbing through as well as any corrosion.

Third, pin 24 is a green wire with an orange stripe, also referred to as a tracer. This wire runs to the instrument cluster and supplies the signal from the vehicle speed sensors from the PCM. Check this wire for any damage or rubbing through as well as any corrosion. Wiggle the connector while watching the dash and see if anything changes. Unplug the connector and inspect both male and female ends for damage.

Finally, the sensors get ground through the PCM on pin 18 using a brown wire. Check this wire as well.

Make sure to check all connector ends for anything loose and be very thorough. You may have to open the entire harness.

I would especially check for a loose connection at the sensor and at the back of the instrument cluster. A female connector that is opened a little more than it should be might not be noticeable but will cause an issue like this. Also, the harness on top of the transmission and behind the cluster are probably more likely to be damaged from movement of the vehicle as it travels down the road over time.

It's possible only on of the sensor harnesses are damaged causing it to connect and reconnect making the gauge go up and down. Just a thought.

Check out this stuff and let me know if you find anything.

Thank you,
Brendon

Hello BDAB68,

You are very welcome! I assumed that's how you did it I just wanted to check.

The signal is sent from the sensor via a white wire to the PCM, then from there goes from the PCM to the cluster via a green wire with an orange tracer. I would start with that one just like you said because the PCM is receiving the signal it's just not getting to the cluster.

Let me know how it goes or if you need anything else.

Thank you,
Brendon

Hello BDAB68,

Hmm. That is an interesting development. So, to me that signals something between the sensors and the PCM. I am willing to bet there is some kind of damage to the wiring on top of the transmission. I would focus on that area. It is the most exposed to the elements and vibrations from the engine. Probably rubbed through somewhere would be my first guess.

I would extensively inspect the harnesses to both sensors all the way to the PCM.

Still no codes though, right?

The ground for those sensors is shared with the ground for the "oil temp" the wiring diagram said. I assume it means for the transmission. See if you can pull the live data for the oil temp and the sensors and see if it is acting erratically too.

Thank you,
Brendon

Hello BDAB68,

Are you having any shifting problems like hard shifting or delayed shifts? Also are you having any engine performance issues such as gas mileage or stalling while driving?

I know your odometer isn't tracking mileage, but can you use the trip meter?

What kind of scan tool do you have? Can you give me the name and model number? I want to try and see what test you can perform with it.

The VSS sends a signal that goes between 5.0v and 0.3v but it happens very quickly. Too quickly to see with a multimeter and possibly a scan tool. You need something called a lab scope or is also called an oscilloscope to see if the signal is dropping out.

So, I am wondering if there is a problem with either the signal the PCM is receiving or the PCM is calculating it incorrectly.

I would check the signal wires from the sensors to the PCM for any damage. If the PCM is getting fluctuating or conflicting signals that would make it unable to make the correct calculations. But if all the inputs are indeed correct and the calculations are wrong it could be an issue with the PCM itself.

It might not have any codes because it keeps resetting itself.

This is all that I can think of for now. I am going to keep thinking from my end and see what else I can come up. Considering the vehicles age and mileage and that most electrical issues are a wire or a connector I would continue looking at the wiring for now.

Electrical issues are one of the hardest things to diagnose, especially since we have no codes to go off of.

Thank you,
Brendon

Hello BDAB68,

No, that doesn't make much sense except maybe what Hyundai is using is different than the global parameters. I would have to look into that to be honest. I am thinking that Hyundai is going to be more accurate than global.

When you have a chance send over those pics so I can see what you are looking at.

Thank you,
Brendon

Hello BDAB68,

Wow that thing is pretty sweet!

I am not sure why it is doing that and found an article I thought you would be interested in:

https://www.vehicleservicepros.com/service-repair/diagnostics-and-drivability/article/21223723/generic-vs-enhanced-data

I am thinking the enhanced OEM is actually catching the issue but the global for some reason isn't.

Thank you,
Brendon

Hello BDAB68,

I added an image. Are these the 2 sensors you replaced?

Thank you,
Brendon

Hello BDAB68,

Okay. That's good you used OEM sensors. I always do the same for sensors and plugs. I am going to continue to look through my information and see what we can come up with here. In the meantime, if you find bad wires or any new symptoms let me know. I'm going to study these diagrams and see if I am missing anything.

At least we know the sensors are good.

Thank you,
Brendon

Hello BDAB68,

You sound like you are doing just fine. It is just a process of elimination. Let's see if we can find out what is giving the computer the speed.

I would try unplugging the wheel speed sensors and take it for a ride and see if it is measuring anything then. If so plug them back in and try unplugging the output sensor and see if that changes anything.

Make sure to use some zip-ties to keep the connectors from touching anything and getting damaged.

Try those two things and let me know your results.

In the meantime, could you please send me your entire 17-digit VIN? I am going to try to look through my Hyundai catalog for some information as well.

Thank you,
Brendon
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