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Hey there
2002 kia magentis (optima USA), the speedometer is jumping around in drive, (up 20kmh in 1 sec, then swing back down) and in park, at zero, goes to 30 then back down.
I have an intermittent check engine light with a P0500 – vehicle speed sensor A.
I ran the scan tool on it, with live data, and i can see the VSS sensor is reading correctly at those times (VSS 0 in park while speedo is going nuts). On the test drive, the livedata also seems to work, changing with speed changes as normal.
Bad cluster or what?? I would expect the VSS reading to be jumping around if it was the sensor, right?
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Were it simply a stepper motor issue there would be no code thrown. Are you sure it’s not throwing odd values for just a couple of frames and you’re just not seeing it?
Well I suppose, i am not sure how often the tool refreshes. I guess ill get a speed sensor then and try that first anyways.
buy cheap VSS off junk yard and swap. See what happens. So far, it points towards VSS. Or, electrical wiring along the line. Bad insulation, mice had fun with it, shorting somewhere. Loose plug/-s.
Replaced VSS with $10 junkyard spare, no change on spedo activity in park. No change on scanner reading of 0 kmh when speedo is jumping around. And it jumps like a lot. I was going to clear the code as well, but the stored code was already gone. Perhaps this car loses codes on battery reset?
FYI the VSS is of the type where there are no moving parts on the sensor by the looks of it.I am going to go with replace cluster.
I find it hard to believe my scan tool is missing the speed changes. When driving it seems to update every 200ms. Wiring before the computer would affect the reading on the scan tool, and wiring after, well I dont want to worry about that just yet!!!
but I could be wrong. Never had this particular problem before.
Does the VSS affect the transmission as well? I haven’t noticed any problems with it.
Seems to be OK. Haven’t seen it jumping around again, except for the first day. I guess it was the sensor.
Just for the heck of it check the system voltage while the engine is running. Sometimes when a diode in an alternator goes bad it lets AC voltage into the electrical system. One of the most commonly effected components is the speedometer due to the nature of it’s operation. If nothing else it’s worth checking system voltage to see if that’s the case. More info on how to check that here.
http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems
God luck and keep us posted.
I constantly monitor system voltage with this:
Generally its 12.9 -14.2 which i think is fine. I’d say case closed for now. Unless the issue re-occurs. I appreciate the help!
well its part of the 12v system. Same as taking a multimeter and putting it on the battery, or any other postive and negative points in the car. You are measuring the difference between positive and negative, not amperage or anything. Basically that’s how electricity works. You can measure anywhere in the system for voltage because its all coming from the same source (battery / alternator). Unless you had a tonne of resistance on a particular circut, but then my number would be off and its in the correct range.
hilariously enough, the issue came back tonight when i was driving. Of course because i just posted it was fixed :P/ speedo went to 0 and then see-sawed around for a bit. The system voltage was 13.7 at the time.
If you mean the lighter socket voltage meter, the first week of having the car I did not have that installed, and that is when I had the most problems with the speedo. I have also used it on a 2 or 3 cars in the past. I like having them installed in all my cars. From deal extreme they are only 5 bucks shipped so why not right. I think maybe you think its just cheap and therefor problematic, but at deal extreme everything is cheap because it comes from HK direct. I have been shopping there for over 7 years and had very few problems with their products. They are just mostly illegal knockoffs of western products, i assume made in the exact same factories.
And its not in the funny lighter socket, its plugged into one of those 12v power ports.
However, next time it does it, i will straight away unplug the socket. Cant hurt.The problem is its my wifes car, and she does not notice the speedo really. I only drive it once a week or so, and it is an intermittent problem. When I bought the car, I received service records with it. They had complained of the speedo jumping around all the way back in 2009, however the dealership could not reproduce the issue and so denied it under warranty at the time. Looking at the air care records (search-able by VIN in BC, so you can see if the car blew any codes when it went through aircare), i could see that the code was set for several years regarding the speed sensor. So I was hoping it was that.
Now if it still does it with another cluster! that would be head scratching time. I am gonna try a cluster swap in the next few weeks. will post back at that time.
Just a status update. I realized that I did not replace the VSS, but rather another induction based speed sensor, forget what it was called now. The VSS had a large orange wheel on it when i pulled it out. So basically i screwed up because i mis read the haynes manual on what sensor it was and the location. When i got a dealer manual, it was clearer that I had the wrong one.
I replaced the REAL VSS with a junkyard spare and have had no problems the last 2 weeks.
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