Question about Code 24

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1BUICKT

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Sep 18, 2011
Hi, I've researched all the boards history on this issue but still need a little help. I'm running an older VDO electric speedometer (with the correct VDO vss) from my ATR dash set up and I'm receiving code 24.

The issue I have with this vs in other topics I've seen is that my speedometer sometimes works... for the most part no but sometimes it reads correct on it's own, out of the blue. Sometimes it may even just fling halfway up from 0 and right back down. Does this sound like a possible faulty speedo causing the code or ???

Any help or input would be greatly appreciated!

Thanks,
Johnny
 
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yes or a bad speedo cable to the vss
that atr is a complicated dash with a motherboard behind the gauges and you may have an issue with the motherboard or the board connection to the dash harness plug
 
pacecarta said:
yes or a bad speedo cable to the vss
that atr is a complicated dash with a motherboard behind the gauges and you may have an issue with the motherboard or the board connection to the dash harness plug
Click to expand...
Ok, so the speedo by itself can cause this. That's what I needed to know. Thanks!
 
There is a local shop near where I that looks to have been in business forever rebuilding/restoring speedometers, I drove by it today but they were closed. I'll disassemble the cluster again and run it over to them for inspection on Monday. Hopefully this will eliminate the issue.
 
the speedo is really just a speaker , if its not acting correct its mostlikely the signal that drives it is whats causing the issue
check the pin that drives the vss sender (is your sender at the speedo cable or at the transmission?
if on a cable could be a bad or binding cable or the cable ends at the trans are worn
if vss sender is being spun properly it could be the buffer (motherboard) or the connections to the board
 
pacecarta said:
the speedo is really just a speaker , if its not acting correct its mostlikely the signal that drives it is whats causing the issue
check the pin that drives the vss sender (is your sender at the speedo cable or at the transmission?
if on a cable could be a bad or binding cable or the cable ends at the trans are worn
if vss sender is being spun properly it could be the buffer (motherboard) or the connections to the board
Click to expand...
The vss is connected at the transmission... If the vss was bad could it cause the speedo to sometimes work... or just not at all? All of the topics related to this subject "Code 24" others have said that their speedo just quit functioning completely when the vss wasnt working properly.
 
And just to double check... do you believe that the speedometer itself could possibly cause this problem if faulty? Thanks
 
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on the stock setup the vss optic relies on the speedometer spinning to generate the signal , the optic is mounted to the back of the stock speedometer and as the speedometer spins its rotates a blade (like a lawn mower blade) in front of the optic and that reflects the optic led to the optical pickup and then sends that to the vss buffer by the radio ..lose the signal due to a non spinning speedometer cable and youll get the code if other conditions are met .. but yours isnt stock..

the conditions for the code are here
http://gnttype.org/maint/malf.html#24

but the cause of the missing vss signal is unique to your setup as the atr doesnt use the speedo to drive the vss.. it has the sender at the transmission that pulses as it rotates and sends signal to the speedo (which drives the needle) and to the vss buffer which feeds the ecu the signal its looking for , in your case i think the buffer is built into the motherboard ..either way the signal is not making it to the speedometer or the ecu so maybe your vss sender is bad , i dont know if the speedometer supplies the power for the vss sender , if it does it could be the speedo or the sender at the transmission or connections at the speedo , if the sender is good and recieving power and outputting a signal then you have to follow the vss signal path and see if it has any connection issues , i dont have a scemat of the ATR function or even its hookups . there was a thread looking for instructions for the ATR dash a few weeks back but i dont think any surfaced
 
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pacecarta said:
there was a thread looking for instructions for the ATR dash a few weeks back but i dont think any surfaced
Click to expand...
That thread was also mine. I was able to get a great deal of help from another member (who has a new/unused unit) in duplicating the harnesses needed to make everything function.

What I'm trying to do is process of elimination at solving this non-working speedo/code 24 issue. The first error that I immediatly see is the on and off working speedo so I figured I'd start there as it seemed to be a rarity with this issue, if it's a possibility of potentially being the cause. I really wish that I could find another to swap it out with just to see if there is any change. Btw, I really do thank you for showing interest in helping me on this.
 
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You could pick up a new vss from jagsthatrun.com if they still have them. The buffer is discontinued but they are/were on eBay for around $50. You could disconnect the cable at the transmission and at the vss, hook it up to a drill and see if it spins. Maybe the cable broke. There is a company on the east coast i believe that repairs speedometers. Do a google search. I had to send mine to them once. If all else fails you could upgrade to a modern vdo speedometer that works off a GPS signal.
 
...fixing the speedo by replacing with a gps unit would still code on the ecm
i wouldn't suspect the OE buffer because the speedo has an issue as well as the ecm so its before the buffer that theres an issue, and that is the vss signal. it could be the vss or the signal wiring to and from the dash that feeds the speedo (and ecm) or the main board has a problem
the electronic vdos dont need the hard to source two pulse vss unit , on his ATR setup i think its a 16 pulse vss and the motherboard takes that and converts it , dont know if the ATR dash converts it to two pulse for the OE buffer or to a signal the ecm can use
if you look at the gnttype code 24 causes
1) Defective or corroded VSS connections
2) Maladjusted TPS sensor. The TPS should read about 0.42 volts at closed throttle
3) Defective speedometer cable
4) Bad or missing speedo drive gear(s) in tail shaft housing of the transmission
5) Defective VSS
6) Defective ECM
because his speedo also has issues and is driven by the vss only 1,4 and 5 apply ...and because of the complicated ATR dash.. the ATR dash and its wiring need to be checked for incorrect wiring or loose wiring

does that electronic speedo go full swing on power up
reason i ask is if it does and you say speedo seems to work all the time and you saw it flip (possibly like it does when powered on) you may be loosing the power or ground to the dash cluster which would interrupt the vss signal processing to the ecm and the code would pop up ..could be a bad connection at the ATR main board contact to the dash harness plug
 
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pacecarta said:
the electronic vdos dont need the hard to source two pulse vss unit , on his ATR setup i think its a 16 pulse vss and the motherboard takes that and converts it , dont know if the ATR dash converts it to two pulse for the OE buffer or to a signal the ecm can use
Click to expand...

I believe that is what I'm running (or that's what I was sold)... the two pulse vdo vss. I purchased it from another board member here as a new/unused unit
 
pacecarta said:
...does that electronic speedo go full swing on power up
reason i ask is if it does and you say speedo seems to work all the time and you saw it flip (possibly like it does when powered on) you may be loosing the power or ground to the dash cluster which would interrupt the vss signal processing to the ecm and the code would pop up ..could be a bad connection at the ATR main board contact to the dash harness plug
Click to expand...
No, on start up the speedo needle is still. I've only occasionally see it fling up while cruising and like I said... it's random and out of the blue. Same can be said for when it functions normally or "as it should".
 
Hey, just wanted to give everyone an update and also ask a question. So I ran my speedo and vss over to my local speedo shop and all checked out great with the two so I started doing more research here on the forum.
What I've found to possibly be the problem is my factory oem speedo driven gear. It doesnt make contact with the vss shaft until halfway down the hole allowing play between the housing and vss. Below is the pic of mine which shows the top of the hole being round and not boxed until further in.
20160220_121012.jpg

This pic that I found here on the forum is more of the style of what I need so it makes contact with the vss shaft sooner.
image (2).jpg

Can anyone please tell me if the TCI replacement is internally boxed all of the way through from the top like the pic above?
 
I've got a VDO mechanical speedo in my car and it uses the in-line speedo cable driven VSS sender.
Years ago, I misplaced the small short connector (square speedo / VSS drive ) cable.......John Spina (Caspers' Electronics) was able to send me one and I was able to get my set up working again. Not sure if this is what you're looking for or not.
 
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