Hello all, great site! I am the proud owner of a low mileage Iroc-Z that just developed a speedometer problem. The check engine light came on and the odometer/speedometer just quit working. I checked the code and am getting a 24 Vehicle speed sensor fault. From what I have read, the VSS is a pulse sensor that translates what the speedometer cable is doing for the PCM so that it can lock up the torque converter. I have a couple of questions. First, would a failed VSS cause the speedometer/odometer to stop working? Second, how do I get the cluster out? I have started and have all of the retaining screws pulled but it won't come out. Do I have to pull the speedometer cable from the back of the cluster to get the cluster to come out? Thanks in advance for all replies.

 

Welcome to TGO. No, a cable-drive speedo will read correctly regardless of the VSS. You must pop the cable from the rear of the cluster to remove it. The following link may be helpful in removal:

https://www.thirdgen.org/forums/faq-...-fix-pics.html

This link may help as well:

https://www.thirdgen.org/forums/inte...eedo-woes.html

JamesC

 

Our cars don't have a PCM , The VSS has nothing to do with torque converter lockup , it simply translates info to the cluster.

 

So does that mean if the VSS is bad the odometer/speedometer won't work?

 

It would be the other way around. VSS is the output of the speed buffer on the back of the instrument cluster (a yellow box) and it's driven by the speedometer. If your speedometer doesn't work, VSS won't either.

Just in case you missed them, there are 2 sheet nuts (10mm) at the bottom of the cluster that hold the connectors tight. Those need to come off as well as the cable to remove the cluster, use a deep well socket. It also helps to lower the steering column just a little.

 

Reread post #2.

JamesC

 

Thanks JamesC. When I first checked back with this thread your post was not up yet, so I was responding to the person who said the car does not have a PCM. I do have an update to the situation with the speedo. I looked under the dash while I was trying to pull the cluster and found the cable still attached to the back of the cluster.(I thought that maybe it had come undone) So, where would you guys suggest I go from here? The cable appears to be hooked up, but I have no speedo or odometer operation. I am thinking that maybe the cable is kinked or split in half somewhere between the tranny and the speedo head. Any opinions? Thanks for the help guys, again, great site!

 

Check post #2, link #2 for suggestions.

JamesC

 

Thanks for the help JamesC. I am going to work on the cluster a little more tomorrow and pull the cable as suggested in the link you recommended. One last thing, I cannot seem to find these 10mm bolts that are mentioned in pulling the cluster. I saw that they are in the holes for the e-brake light, but I am not seeing them. Could you point me in the right direction? Thanks for all of the help.

 

You need to look all the way down inside, one sits next to th bulb for the brake light and the other next to the bulb for the service engine light. It's possible to mistake them for bulbs if you don't know where they are.

 

ok if your speedometer stopped working and u are getting a VSS code i would assume your cable is no longer turning, which would mean one of 3 things. A the cable popped off the back of the cluster (unlikely) B. the speedo gear in the trans broke or stripped teeth, (more common) C. the cable snapped (never seen ithappen but heard of it on other cars) there are your options, i would pull the cable out of the trans and check the gear, and if it looks good have someone sit in the car and watch your speedo as you spin the gear by hand. if that works then you know your problem, if not well come on back lol.

 

ok my question is are the camaro and firebird VSS different? i have a 89 GTA and work on my friends 88 GTA all the time. i know in our cars there is no speedo cable. my speedo is run by the VSS and ECM. in the case of the firebird if the VSS were to stop working so would the speedo. does anyone know if the camaro still runs a cable and firebird doesn't?

 

The Camaro is cable driven, 82-89, the Firebird is electric 86+, IIRC.

JamesC

 

thanks for the answer. i was wondering about that as i was reading the thread.

 

Ok, I have an update for all following along. I removed the cluster and the speedometer cable looks good, no fraying or splits that I can see. Thanks Chevy 8588 for the advice on checking the speedometer gear, I am going to do that tomorrow. Any advice on making this job easier? It seems that I just pull the cable out of the transmission, then pull the gear out and replace it with a new gear if it is broken/has stripped teeth. Sorry about all of the questions, I feel ashamed asking because I am a service manager by trade and know my way around a car, but I am used to newer vehicles with electronic instrument clusters and hardware. This is my first 80's car with older tech that I have owned so I am getting a bit of a crash course!! I did pull the throttle body today and clean/adjust the IAC valve, much better/smoother idle now. Thanks to all who have helped me try to get my speedometer working again.

 

Ive taken out all the screws on the guage face and can take the clear plastic piece of the cluster off but the damn thing wont budge out! the bottom dash piece is off but i dotn see where this can come out of to swap... i have an 88 IROC, sorry for zombie-ing the thread but didnt want to make a new thread after i searched