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

Unfortunately, I don’t have anything that can monitor the wheel speed sensors for this car. My scan tool will be for my Nissan but not for my Hyundai. From my understanding this car only uses them for the antilock brakes. Not to monitor vehicle speed. Correct me if I’m wrong. I don’t physically see any issues with any of the wires for it. No ABS light on or any engine codes. As for the tires they are in good shape. Purchased a set of 4 about 1 year ago. Good tread depth all around. Tire pressure is good as well.

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

Thank you so much for the wiring diagrams. I will try and trace them all and see if I can identify any issues. As for the test I performed. I hooked up my scan tool via OBD2 port. Checked live data while driving the vehicle. The speed showed up accurately and steady on the scan tool. It stayed at 0 on the speedometer. This told me the issue is likely between the computer and the cluster. I assume the wire travels from VSS to ECU than to the cluster. Or does the signal split and go directly to both? I will check the wiring diagram you provided and get back with you. Thanks again

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

Hey buddy so I checked the wiring a bit but didn’t have time to fully examine it. However, I figured out how to fully use my scan tool lol. I found out some good info that might help us. So, all 4-wheel speed sensors are good. The vehicle speed sensor is good. The transmission input and output sensors are reading but I’m unsure of what their values should be. It was showing around 1,000-600 rpm going around 20mph. The odd thing is it said my vehicle speed was all over the place. 127mph 168mph 40mph etc.

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

Correct no codes at all. I will check the oil temp sensor data. My wife took the car to work so I’ll get more thorough this weekend when I have time to dig deeper into the wiring. Yeah, it’s very odd to me that all speed sensors (wheel and VSS) were reading at the correct speed, yet the computer has the speed all over the place. The Speedometer stays at 0 and hasn’t moved. No mileage being tracked. The cruise control hasn’t set and no codes saying any malfunctions are happening. Mind blowing to me. I had the vehicle with my mechanic, and it worked fine both days he had it. He tried wiggling wires and connectors to get it to not work. I took the car back and it worked for a week before it started back up again. I can take a car apart and put it back together but when it comes to electrical issues my mind blows. I do have a multimeter though so if you have a good test for me to try at the harnesses let me know. Note I’m a dummy with electrical so I would need steps lol. I can’t thank you enough for helping me with this.

Okay so I did some more monitoring with my scan tool, and I don’t understand something strange. When I go into "Global OBD2" live data it shows engine RPM and VSS accurately. When I go into Hyundai OEM enhanced live data powertrain vehicle speed and engine speed are high. Transmission live data input and output speed sensors are correct. I took some photos for you. This is at idle and not driving. I pulled the fuse to ECU and waited 30min to see if a reset would fix it. It had no effect. The oil temperature sensor stays consistent. Any ideas as to why the live data when in OEM enhanced would be so different compared to OBD2 Live data? Could this have something to do with my issue?

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

I have an innova 5610 scan tool. No the trip computer doesn’t work either. It remains at 0. No shifting issues or stalling. Car runs good. Not sure my photos loaded on last post so I’m adding them here.

This was taken when idling. The VSS and engine RPMS seem normal under OBD2 live data. The VSS changes accurately when driving. Same goes with the input and output transmission speed sensors. Under ABS live data it shows all 4 wheel speed sensors and they are accurate as well. However, when I go to OEM enhanced live data it shows my vehicle speed at 127mph and engine RPMS around 50,000rpms. This is at idle. I don’t understand why data is so different.

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

Yes. Actually, I replaced 3. The VSS that is shown in the picture along with a new driven gear. Also, both input and output transmission speed sensors. Here are pictures of what I replaced. I used all Hyundai parts ordered from Hyundai OEM parts.

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

Thank you. Yes I didn’t have time today to get behind the dash. I inspected the wires inside the engine bay but they all look good. I see no evidence of any issues with them.

Okay, so more interesting info. Apparently, the scan tool doesn’t pull speed info from the VSS like it says it does. I disconnected the speed sensor and sure enough it still showed the speed on the scan tool. So, I’m back to square 1. I tested the VSS connector and my results I believe show an issue. I’m not good at this so hopefully you can help. First off, I tested the ground. With black probe of multimeter in negative terminal of connector and red probe on positive battery terminal I get 3.5V. With black probe still in negative wire terminal and red probe on what I believe is the signal wire I get 2.5V. On the power supply terminal, I’m only getting 2.78v and I believe that should be 12v. Where do I go from here?

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
2CarPros

The VIN is KM8JM12BX5U121871.

I did unplug the VSS, and it continued to show speed on the scan tool under vehicle speed sensor. So, it’s confirmed that the scan tool gets speed from something else. I read it gets it from the front wheel speed sensor.
I noticed that if I use the ground on the battery terminal, I can get 11.95v from the power supply terminal of the VSS connector and 10.4v on the signal wire. If I move the black probe back to negative terminal on the connector it drops voltage to 2.5-3v. I don’t know if that’s indicating a bad ground to the VSS or not. I’m trying to educate myself more about this. Electrical issues make my brain hurt, lol.

Hello BDAB68,

I can appreciate your hunger for knowledge, especially for electrical. I always liked it myself, but you can get burnt out quickly and start over thinking it. If you reach that point, take a break and think about it and go back and approach it with a clear mind. Check the entire harness for any issues starting at the sensor.

Here are a couple articles that will help you:

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Read the articles and do some testing and let me know if you find any damage. If the computer is getting the speed but it isn't making it to the cluster, then it could be the PCM or the wire that sends the signal from the PCM to the cluster. I would continue testing all the wiring by following these 2 articles.

Finding a faulty wire or connector can be like finding a needle in a haystack. So be patient and take your time and most importantly don't overlook anything. Pick one section at a time and isolate and test that specific area and record your results.

If it were my vehicle this is exactly what I would do.

Thank you,
Brendon
2CarPros

Thank you so much. That was some much-needed knowledge. I’m feeling confident that it’s a bad ground to the sensor. Now it’s determining where the break is. I’m trying to study the wiring diagram. I enclosed a photo of the one I found. If you have a better one let me know. At the bottom left of the diagram it shows a ground. Would that be the ground to the sensor? I don’t see any other grounds in the diagram. What is Hall IC in the diagram with the speed sensor. Thanks for the help.

Good morning, BDAB68,

You are very welcome. A bad ground is definitely a good possibility. Considering the vehicle age and mileage, a wiring issue is something I would be looking for myself. The Hall IC is a Hall Effect Sensor. I have included a video that explains how a Hall effect sensor works to give you a better understanding to aid you in diagnosis.

https://youtu.be/MEpZRcPZGxM

As far as the wiring diagram, I am not sure. You have to be careful what you get from the internet. I am working on getting a better diagram for you. Sometimes I find it helpful to draw my own as some of these wiring diagrams can be confusing and hurt your brain lol. But sometimes certain information is just not available.

But do the best you can to follow the wires and see where they are going. Previous diagrams I have looked at says the PCM is under the left side of the dash so the ground might lead close to that. The PCM may also be providing the ground.

Continue to work on it and see if you can find a bad ground and I will continue on my side to see if I can get you some better diagrams.

Thank you,
Brendon
2CarPros

Hello,

I wanted to jump in here if I could, the speedometer signal is generated form the cruise control module via the VSS, I would swap out the module to see what happens, here is the wiring diagrams so you can see how the system works and the location of the module in the images below. Please let us know what happens. I also see the spiral spring behind the steering wheel could cause the problem as well. A questionable connection through the spring would produce the same effect.

Thank you, Ken. I think my issue is the ground on the sensor. The reason being is using my multimeter when I use battery negative than touch the power source connector on VSS harness I get 12v. The signal wire gives me 10v. However, if I move my negative probe to the ground terminal on the connector, I get a big voltage drop. Only reading 2.7v on supply and 2.5v on signal. From your diagram it looks like the ground for the sensor is at the body in engine bay. So, splicing in a new ground should hopefully fix it. If it doesn’t then I will go into looking more at the cruise control module. I really appreciate all the help I’m getting with fixing this problem. I’ve learned so much and keep learning more thanks to you all.

So, I ordered a new replacement VSS connector. I have a theory that might let me test if it is in fact the ground before I go splicing wires. My unorthodox thought is to hook up the new connector to the VSS then take the leads and place them in the original connector routing the ground to a new ground. See if the speedometer works. If it does, I’ll install the new connector and ground. If it doesn’t then I need to do some more digging. Perhaps like Ken said my problem lies in the cruise control module. I’m however feeling confident it’s a ground issue. It just surprises me that no codes are popping up. Usually, a bad ground would throw a code. Maybe that system isn’t monitored by the computer.

Yep, it should, that is why I thought it would be the cruise module shunting the signal.

Well, I got it figured out. It was a bad ground. I did like I said to test it out. I got a new connector and ran the power and signal wire leads into the original connector. Then ran a temporary ground to the new connector lead and the speedometer worked. So did cruise control. Now I just need to splice in the new connector and run a good ground. I honestly can’t thank you enough for all your help with this. I have learned so much and now feel confident on how to test wiring. We can now consider this solved!!

Good morning, BDAB68,

That's awesome! Glad to hear it! Wiring problems are one of the hardest things on a vehicle, I am happy to hear you figured it out and that I could help you along the way. Nice job. If you need anything else, please do not hesitate to come back and start a new question. We are here to help any way we can. Enjoy your speedometer! It was a pleasure working with you.

Thank you,
Brendon
2CarPros

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During winter the speedometer stopped working. After diagnosing a faulty ground wire, I ran a new ground from the VSS to the chassis. This fixed the speedometer, but I never did figure out if any other sensors shared the same ground as the vehicle speed sensor. So, I’m wondering if the engine coolant temperature sensor shared the same ground wire as the VSS. They are located close to each other and join together into 1 big wire harness. My only thought though is, I assume if the sensor wasn’t working then the temperature gauge would not be either. Looking at my vehicle it appears the sensor is also the sender to the dash. If it’s not and the dash actually gets the temperature from something else, then my issue could very well be the engine coolant temperature sensor. I don’t have any schematics or diagrams to go by. So, I’m hoping with your knowledge and resources you can help me out in diagnosing this issue.