Speedo is dead. New VSS already. HELP!!!
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Junior Member
Joined: Jun 2008
Posts: 18
Likes: 0
From: Los Angeles, CA
Car: 1991 Camaro RS 5.0
Engine: TBI 5.0L V8
Transmission: 700R4
Axle/Gears: 2.73
Speedo is dead. New VSS already. HELP!!!
I have a 91 RS 5.0 TBI. My speedo is dead and the cruise didn't work also. Check engine light was on and it threw a 24 code (VSS). So I replaced with a new VSS. Speedo is still dead but no check engine light anymore and the cruise control works now. What is the problem now? Buffer box or ECM? Thanks for any help you guys can give me.
Supreme Member
iTrader: (3)
Joined: Jul 2004
Posts: 2,989
Likes: 9
Car: '91 Z28 convertible
Engine: TPI
Transmission: T5
Axle/Gears: 3.27 posi disc
Re: Speedo is dead. New VSS already. HELP!!!
Good troubleshooting, kudos. 
So we know that the buffer box is sending signal to the ECM and cruise module. Now you need to find out whether the speedometer doesn't work because:
1) the buffer box isn't outputting any signal on the wire to the speedometer
2) the wire to the speedometer is broken
3) the speedometer itself is bad
Do you have a friend with another 90+ Camaro with whom you could swap the instrument cluster for a minute? That would tell you if the speedometer is good/bad.
Also, do you have a friend with a TBI engine with whom you could swap the yellow buffer box for a minute? Again, that would tell you if the buffer box is good/bad.
Btw, was the speedometer always dead? Or when did it die?
If you still can't figure out what's wrong, I'm working on a simple and cheap VSS simulator that would help you find the problem. Right now it's in the drawing stage but hopefully I'll make one soon (this week).
Hope this helps.
Lou
So we know that the buffer box is sending signal to the ECM and cruise module. Now you need to find out whether the speedometer doesn't work because:
1) the buffer box isn't outputting any signal on the wire to the speedometer
2) the wire to the speedometer is broken
3) the speedometer itself is bad
Do you have a friend with another 90+ Camaro with whom you could swap the instrument cluster for a minute? That would tell you if the speedometer is good/bad.
Also, do you have a friend with a TBI engine with whom you could swap the yellow buffer box for a minute? Again, that would tell you if the buffer box is good/bad.
Btw, was the speedometer always dead? Or when did it die?
If you still can't figure out what's wrong, I'm working on a simple and cheap VSS simulator that would help you find the problem. Right now it's in the drawing stage but hopefully I'll make one soon (this week).
Hope this helps.
Lou
Thread Starter
Junior Member
Joined: Jun 2008
Posts: 18
Likes: 0
From: Los Angeles, CA
Car: 1991 Camaro RS 5.0
Engine: TBI 5.0L V8
Transmission: 700R4
Axle/Gears: 2.73
Re: Speedo is dead. New VSS already. HELP!!!
Good troubleshooting, kudos.
So we know that the buffer box is sending signal to the ECM and cruise module. Now you need to find out whether the speedometer doesn't work because:
1) the buffer box isn't outputting any signal on the wire to the speedometer
2) the wire to the speedometer is broken
3) the speedometer itself is bad
Do you have a friend with another 90+ Camaro with whom you could swap the instrument cluster for a minute? That would tell you if the speedometer is good/bad.
Also, do you have a friend with a TBI engine with whom you could swap the yellow buffer box for a minute? Again, that would tell you if the buffer box is good/bad.
Btw, was the speedometer always dead? Or when did it die?
If you still can't figure out what's wrong, I'm working on a simple and cheap VSS simulator that would help you find the problem. Right now it's in the drawing stage but hopefully I'll make one soon (this week).
Hope this helps.
Lou
So we know that the buffer box is sending signal to the ECM and cruise module. Now you need to find out whether the speedometer doesn't work because:
1) the buffer box isn't outputting any signal on the wire to the speedometer
2) the wire to the speedometer is broken
3) the speedometer itself is bad
Do you have a friend with another 90+ Camaro with whom you could swap the instrument cluster for a minute? That would tell you if the speedometer is good/bad.
Also, do you have a friend with a TBI engine with whom you could swap the yellow buffer box for a minute? Again, that would tell you if the buffer box is good/bad.
Btw, was the speedometer always dead? Or when did it die?
If you still can't figure out what's wrong, I'm working on a simple and cheap VSS simulator that would help you find the problem. Right now it's in the drawing stage but hopefully I'll make one soon (this week).
Hope this helps.
Lou
Supreme Member
iTrader: (3)
Joined: Jul 2004
Posts: 2,989
Likes: 9
Car: '91 Z28 convertible
Engine: TPI
Transmission: T5
Axle/Gears: 3.27 posi disc
Re: Speedo is dead. New VSS already. HELP!!!
The buffer box is usually next to the ECM, up in the dash on the passenger side. Not hard to get to at all. It's a bright yellow box, can't miss it. 
Do a search here, somebody recently posted about the buffer box and where you can get one for a decent price.
In my opinion (from my experience), if two of the three outputs on the buffer box are good, I'd more suspect the speedometer or wire.
If your tachometer is out of adjustment and you'd like it fixed, you can send it to me and at the same time, I can test the speedometer to see if it works. PM/email me if interested.
Hope this helps.
Lou
Do a search here, somebody recently posted about the buffer box and where you can get one for a decent price.
In my opinion (from my experience), if two of the three outputs on the buffer box are good, I'd more suspect the speedometer or wire.
If your tachometer is out of adjustment and you'd like it fixed, you can send it to me and at the same time, I can test the speedometer to see if it works. PM/email me if interested.
Hope this helps.
Lou
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