Code 24: VSS
Thread Starter
Instructor
Joined: Dec 2013
Posts: 142
Likes: 0
From: Bothell WA
Code 24: VSS
My '85 with a Richmond 6 (swapped from a 4+3) has been dying a lot. I finally got a hold of an OBD1 scanner and I was trying to force kill it (so I could scan the CEL- goes away after I turn back on) by revving up to 4k and let off the gas. Didn't die, but I got a Code 24.
I'd like to trouble shoot first by checking the sender in the circuit. Where is the thing located though?
I'd like to trouble shoot first by checking the sender in the circuit. Where is the thing located though?
Drifting
Joined: Feb 2006
Posts: 1,423
Likes: 96
From: Magnolia Tx
The VSS is in the tailshaft of the transmission. Does the speedometer work? If not, the ECM won't handle deceleration idle control very well. I swapped in a T56 and drove it around without the speedo and my car died at nearly every stop, code 24. I hooked up the speedo (with a converter box) and the issue went away totally.
Team Owner
Joined: Sep 2003
Posts: 25,393
Likes: 2,741
Did you do the 6spd conversion or was it in the car when purchased? I believe the Richmonds all use a VSS like the T10 and the VSS would have been a specialty unit I'd think and the actual conversion VSS to cluster/ECM done probably by a DRA and maybe the DRA has failed you or maybe just a connection to the DRA. If it has a DRA you need to attempt an ID of the branding.
You mention the speedo works so I'd guess the signal is fine to the cluster and the cluster I believe is the "first stop" from the VSS and the signal is distributed from there.
A good thing is that if you find the DRA you can correct the speedometer error using the dip-switches. You mention the error at 5mph BUT that can only be correct at one particular speed. A speedometer error should be a consistent percentage from actual. You could check with a GPS using various speeds and comparing.
I'd be interested in seeing what you actual find for the VSS and also a DRA that I expect will be there.
You mention the speedo works so I'd guess the signal is fine to the cluster and the cluster I believe is the "first stop" from the VSS and the signal is distributed from there.
A good thing is that if you find the DRA you can correct the speedometer error using the dip-switches. You mention the error at 5mph BUT that can only be correct at one particular speed. A speedometer error should be a consistent percentage from actual. You could check with a GPS using various speeds and comparing.
I'd be interested in seeing what you actual find for the VSS and also a DRA that I expect will be there.
Last edited by WVZR-1; Mar 26, 2014 at 10:08 PM.
Thread Starter
Instructor
Joined: Dec 2013
Posts: 142
Likes: 0
From: Bothell WA
It was done before I bought it. I have no idea how the swap was done. It's 5mph at 65,so in actuality I'm at 60mph. I figured it out with a GPS Speedo.
Looks like I've got a fun weekend ahead of me.
Looks like I've got a fun weekend ahead of me.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
You got a code 24 because you revved the engine but the car was not moving. It just means that there is no VSS signal getting to the ECM, which there won't be if the car is not moving.
The VSS signal goes to the instrument cluster and from there it goes to the ECM. That's why knowing that the speedo works tells us that the VSS is also working.
The VSS signal goes to the instrument cluster and from there it goes to the ECM. That's why knowing that the speedo works tells us that the VSS is also working.
Thread Starter
Instructor
Joined: Dec 2013
Posts: 142
Likes: 0
From: Bothell WA
You got a code 24 because you revved the engine but the car was not moving. It just means that there is no VSS signal getting to the ECM, which there won't be if the car is not moving.
The VSS signal goes to the instrument cluster and from there it goes to the ECM. That's why knowing that the speedo works tells us that the VSS is also working.
The VSS signal goes to the instrument cluster and from there it goes to the ECM. That's why knowing that the speedo works tells us that the VSS is also working.
Team Owner
Joined: Sep 2003
Posts: 25,393
Likes: 2,741
If the trouble code reappears and you still have a problem with the code 24 you'll need to look further. I wouldn't go looking unless you had further problems.
I wouldn't pull the VSS until I had ID'd the type of VSS that has been used. Since a Richmond uses I believe the T10/Muncie type cable drive I'm guessing the VSS is unusual in appearance likely connecting to the transmission with an old style nut or might also be like the one on the extreme left in this image:
I wouldn't tear into it. Take a snapshot of it! It might also be maybe cable driven to a remote mount. Do you recall at all?
The rev to 4K exceeded likely what the ECM is expecting for a signal with no VSS signal from the speedometer and set the code. I'd look elsewhere after clearing codes for a run problem.
Last edited by WVZR-1; Mar 27, 2014 at 11:18 AM.
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