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2008 Accent speedometer/odometer doesn't work

43K views 76 replies 8 participants last post by  AUTOSPARK  
#1 ·
I have a 2008 Accent two door hatchback. The speedometer started jumping and then just quit along with the odometer. The odometer displays the last mileage but doesn't increase. I replaced the speedometer sensor in the side of the transmission and found two of the pins on the connector socket going to that sensor were burnt. I have now replaced the three connector, cable and it still doesn't work. The Hyundai part number for the HMC Extension cable is 43893-23011. So, I have a new cable and new sensor. What next?
 
#44 · (Edited)
its listed on the diagrams in tiny numbers and the color codes. Have you ever read a wire diagram before? On the computer plug you will see numbers posted on the pins. These line up with the numbers on the diagrams. example pin 1 goes to pin so and so on the other connector. The connector is labels E50 R20 and so on. You will look for the speed sensor on the posted diagram and look at the pin numbers then look at the computer connector and you will see pin numbers. Attach your dvom to the correct pins on each one on the speed sensor then the other on the computer pin that is UNPLUGGED. And see if you have continuity. This will tell you when you put your new wire on it is installed correctly. Like autospark I would assume he would disconnect the computer plug and probe each pin tell the dvom reads continuity. I would use a power probe with an audible alert. It will take less than 1 min to find the correct wire to each end to fix without a wire diagram. I'm just lucky to own the entire manual.

E50 has 2 pins labeled pin1 pin2. computer c01 has pins 79 and 58.

Look at the wire diagram and check each wire according to the diagram. You can jump a new wire to bypass the broken wire to save time from cracking open the wire harness. Or you can buy a wire probe to connect a sound module to one end and probe the wire harness until the sound disappears then you will find the break in the wire if you have no continuity. Vibrations in the wiring is causing a connect no connect causing your drop out of the wheel sensor. The fired end I would suspect a power wire shorting a ground. This means the power V+ is touching GRD. This causes heat and then a melted connector. Also high resistance in a circuit like the blower motor can do the same where the motor is turning and gets debris in it causes resistance that backs into the wire MELTING the connector. Find the break then cut out the bad part and twist the wires and solder and heat shrink tube the patch. You will find that either the outer cable sheathing is broken or the wire is exposed and the wire is touching ground car body or engine block or an adjacent ground wire in the wire harness. The wires vibrate which explains the sensor reporting then falling of. I am not a ASE mechanic but do understand the concepts or reading diagrams and fixing cars.

This is important to TEST the wires to senors before assume the sensor is bad. Ive seen many posts here replacing purge valve, o2 sensor only to find out its not working. Then they find out later the wire connecting the computer is shot. Then there out the cash for the new part when it would have cost 10 cents to fix their car. Same goes with coils. Always use electric grease on the ends as this prevents moisture which can cause coils to fail premature. I use platinum plugs by bosch that have 4 contacts on the ends. Ive never replaced a coil and the car has 150,000 klm on it and it runs great. follow these tips and you will save these coil nightmares.
 
#45 ·
I do have a little experience. I installed and repaired aircraft radio and autopilot systems for four years before starting my life career as a State Trooper. When I asked which pins, I didn't see on the diagram you posted where the three pin speed sensor connects to the PCM. That is what I was looking for. The block diagram you posted looks like it is for the MFI components. So a question I don't understand, why does it use a speed sensor on the back of the transmission if it runs on a sensor off of one of the front wheels? I don't have ABS. Back to my problem. I can connect my DVM to the pink wire on the speed sensor on the back of the transmission and probe all of the pins on the PCM connector but if the pink wire is open between them, I will never know which pin it should be on the PCM connector. That is why I wanted to know that so I could back track from there if it were open. Now if the wire stays pink thru the whole harness, that would make it easier but don't know that. Thanks for all the help so far.
 
#46 ·
Now after reading thru your response several times, it seems we are talking about two difference sensors. I have been referring to the vss sensor on the back of the transmission where the pink sensor wire (and red positive wire) and connector were burned. Probably from being corroded from some source. You have been talking about a speed sensor on the right front wheel. I will check that to make sure it wasn't disconnected during the engine change out but still don't understand why two speed sensors. If the wheel sensor is what the computer uses to make the speedometer work, what purpose does the vss sensor on the back of the transmission serve?
 
#48 ·
... still don't understand why two speed sensors. If the wheel sensor is what the computer uses to make the speedometer work, what purpose does the vss sensor on the back of the transmission serve?
The ECU uses two inputs to determine if the information it receives is correct.
If they don't correlate properly then the transmission can be put into limp home mode.
It is some sort of safety feature to protect the transmission and engine.
 
#50 ·
Looks like red wire goes from speed sensor to you speedo panel and the black goes to ground the the pink goes to v+ 10 amp fuse. Think this is the correct info. So I guess check red wire pin 3 on speed sensor red wire connector c22 to red wire at m09-3 connector pin 11 on the speedo panel plug. This should fix your odo speed drop off problem if that is what you are trying to fix.
 
#51 ·
Thanks for the diagrams Ken, but it would be a big help to aztrooper if you could advise him on the locations of the harness connectors in the diagram of the VSS (post #47 ). That would be connectors CC03, EC03 and EM02.

aztrooper : use the diagram from post #47 and check for voltage on the signal wire at each harness connector starting at CC03 and work your way towards the speedo. That should help you narrow down which section of the loom the break is in. If you want to narrow it down further you'll need to probe the wire at various points along it's length in the effected section of the loom.
 
#56 ·
Thanks again for all the help. Haven't had the time to try to track it down yet as I have been very busy. Now it's record hot and getting hotter next week. Supposed to be 120 next Sunday and the clutch has gone out. My daughter was driving it to work and hit a 2x4 or something last week and blew the RF tire out. The next day the throw out bearing started making a noise when the clutch was engaged. Next trip the clutch went out. I can push in the clutch pedal, the clutch hydraulic cylinder pushes the fork forward but nothing happens. Can't even get it into a gear when the engine is not running. Going to have a local mechanic pull the tranny and see what is going on. I told her it was just a coincidence that it happened at the same time (I hope).
 
#57 ·
A lot of of things happening lately since I last posted. Traveling back and forth every other week to work on our barn/house up in the White Mountains so we can move out of this heat. Got the clutch replaced, sort of. Ordered the clutch kit and it had the wrong pressure plate in it. Needed the car and had the appointment made to have it replaced so just went ahead and put the new throw out bearing and clutch disc in and sent the pressure plate back. It was the throw out bearing that had gone out so wasn't worried about the pressure plate anyway. Going to get rid of this car anyway. Don't buy spark plug coils on Ebay, even with lifetime warranty. They last about two months and the seller gets tired of replacing them. On my last one now and have been replacing them with ones bought at an autoparts store that also has a lifetime warranty but they have not gone bad after a year. Now on to the speedometer. Haven't had time to get deeper into it lately. Daughter was driving it and got a ticket so time to get back to it. Checked a couple of connectors before it got to hot and they looked good but I need to get a new 9v battery for my multi meter before I can move on. Let you know what I find.
 
#58 ·
Do you have a GPS? If not, buy a cheap TomTom on eBay for a few bucks. Mount it in plain sight, and set the display to show the speed and few other things. It doesn't fix the speedo, but at least you'll know how fast you're traveling, and it's a LOT cheaper than tickets! ;)
 
#60 ·
"Do you have a GPS? If not, buy a cheap TomTom on eBay for a few bucks. Mount it in plain sight, and set the display to show the speed and few other things. It doesn't fix the speedo, but at least you'll know how fast you're traveling, and it's a LOT cheaper than tickets! ;)"

She was using it but hasn't been lately. I showed her that all she had to do was when it is in 5th gear, all she had to do was double the RPM reading and that would be very close to her speed. She wasn't paying attention.
 
#63 ·
I went out this morning to change the last of the cheap Ebay coils that went bad after two weeks and put in another O'Rielly's coil. While there and before it got to hot, I opened the fuse cover inside the car and looked over the fuse labels. Checked two that I thought might be the right one and they were good. I went back inside and checked the flow chart on page 5 of these posts and found the fuse was labeled TCM. Found that, pulled it and it was blown. Put in a spare 10a fuse and my daughter drove it to work. She called me and said the speedometer was not working but was doubling the actual speed meaning that at 65mph on her GPS, the speedo showed 135mph. Odometer corresponds with the speedometer. Would that be maybe a blown diode in the speedo module on the back of the speedometer?
 
#66 ·
Any body got any idea on this? Should I just buy a junk yard speedo?
Several posts back (post #23) you checked the voltages at the gearbox speed sensor and you found there was no voltage on the pink wire. At that time we were working without a circuit diagram and I mistakenly assumed the pink wire was the sensor output. Someone then kindly uploaded a wiring diagram (thanks Ken) that shows that the pink wire is actually the 12V power supply to the sensor. The speed sensor wont work without a 12V supply so did you ever trace where the supply wire was open circuit?

No, I don't think a junk yard speedo will help. You seem to have already discovered the cause of the problem. You just need to either trace and repair the open circuit and all should be well.

Regards.
Scott.
 
#67 ·
The pink line is the 12v line. As in the post above yours, I found that the pink line went to the TCM fuse that I found blown in the fuse box. I now have 12v on the pink line and the speedometer works but is reading twice as fast as it should, ie, at 65 mph actual, it is reading 130 mph. At all speeds, it is doubling the actual speed and the odometer is corresponding with the speedometer. Checking the odometer between mileposts, it is advancing 2 miles for every 1 mile the car goes. That's why I'm thinking it is now a speedometer problem. When the TCM fuse blew because of what ever happened to the original connector and speed sensor unit causing it to burn, it may have damaged some component in the actual speedometer circuit. Does that sound right?
 
#68 · (Edited)
Sorry for the misunderstanding. I should have gone back and re-read your earlier post where you mentioned the blown fuse.

When the TCM fuse blew because of what ever happened to the original connector and speed sensor unit causing it to burn, it may have damaged some component in the actual speedometer circuit. Does that sound right?
I think it is more likely your replacement sensor is incorrect. Was it a genuine Hyundai part?

I've never worked on your model of Accent before but from experience on other Hyundai models I know that the VSS should output 4 pulses per 360' of rotation of the drive gear. Before replacing the instrument cluster it would be worth confirming that your VSS is sending out the correct number of pulses. The number of pulses the sensor sends down the signal wire effects how far the needle is deflected on the instrument. Too many pulses = too high a speed displayed. You should be able to test it by removing the VSS and rotate the drive gear by hand while monitoring the voltage on the signal wire by back probing the connector.
 
#70 · (Edited)
Yeah, it's what is called a pull down sensor circuit. The instrument cluster outputs a voltage on the signal wire and the sensor pulls/pulses that voltage down to ground 4 times for every 360' of rotation.

To test it, remove the sensor from the gearbox and plug it into the harness. Connect your red voltmeter probe to battery positive and back probe the black into the signal terminal on the sensor connector. Turn the sensor drive gear until your meter shows a low voltage (maybe 2~3V) and take a note of the position of the drive gear. Now rotate the gear through 360' and count how many times the meter shows 12V. You should see four 12V pulses for every 360' you rotate the gear.
 
#72 · (Edited)
Well, this thread has dragged out for quite a while. I want to close it out so if anyone else has this problem, they will know how it was solved. Original problem was no speedo or odometer. The speed sensor connector in the back of the transmission was burnt. I replaced the short three leg harness, speedo sensor (Ebay special) and it still didn't work. After the circuit diagram was uploaded and I could see where the three leads from the sensor came from, I found the TCM 10a fuse blown. After replacing that, the speedo worked but the speedo read twice the actual speed. I replaced the speedo sensor again with a sensor that I got from Hyundai using the VIN number and now it works properly. What I learned from this? 1. Whether it is spark plug coils or speedometer sensors, get them from Hyundai, NOT EBAY. 2. Have a wiring diagram available makes tracing circuits much easier. 3. I will NEVER buy another Hyundai.

Thanks to everyone who helped.
Bob
 
#74 ·
I have had similar things happen with Toyotas and other cars. Had a brand new Corolla that needed a whole harness and 2 that needed throw out bearings. Similar thing happened (speed sensor) with a Chrysler.

However, glad you got to the bottom of it. Now you can tell us how many miles are on the car...:D