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Speedometer stopped working?

Tiny
BDAB68
  • MEMBER
  • 30 POSTS
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.
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Sunday, March 12th, 2023 AT 11:41 AM
Tiny
BRENDON S
  • MECHANIC
  • 651 POSTS
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
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Sunday, March 12th, 2023 AT 12:13 PM
Tiny
BDAB68
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  • 30 POSTS
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.
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Monday, March 13th, 2023 AT 6:01 AM
Tiny
BRENDON S
  • MECHANIC
  • 651 POSTS
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
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Monday, March 13th, 2023 AT 7:52 AM
Tiny
KEN L
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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.
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Monday, March 13th, 2023 AT 8:22 AM
Tiny
BDAB68
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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.
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Monday, March 13th, 2023 AT 9:13 AM
Tiny
BDAB68
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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.
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Monday, March 13th, 2023 AT 9:48 AM
Tiny
KEN L
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Yep, it should, that is why I thought it would be the cruise module shunting the signal.
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Monday, March 13th, 2023 AT 12:23 PM
Tiny
BDAB68
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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!
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Wednesday, March 15th, 2023 AT 8:53 AM
Tiny
BRENDON S
  • MECHANIC
  • 651 POSTS
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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Thursday, March 16th, 2023 AT 1:37 AM
Tiny
KEN L
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BRENDON S is one of our best! Can you please leave us a rating? (copy entire link)

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Use 2CarPros anytime, we are here to help. Please tell a friend.
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Thursday, March 16th, 2023 AT 9:48 AM
Tiny
BDAB68
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  • 2005 HYUNDAI TUCSON
  • 250,000 MILES
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.
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Tuesday, June 20th, 2023 AT 4:15 PM (Merged)

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