Speedo odometer abs issues

[ethanthatcher777]

Anyone have their drac die on them? speedo isn't working neither is abs, odometer and trip meter. speedo starts moving when going 45+ mph replaced vss parking brake light turns on when braking and stays on. 1990 v10 blazer

 

[ZooMad75]

If the abs is taking down the signal, it may kill the speedo. The vss signal goes to the DRAC and then sends signals to the cluster, PCM and ABS module. Pretty easy to disconnect the ABS and see if it starts working again.

The module is discontinued anyway, besides being a half-assed setup to begin with. I pulled mine and deleted it all.

 

[ethanthatcher777]

If the abs is taking down the signal, it may kill the speedo. The vss signal goes to the DRAC and then sends signals to the cluster, PCM and ABS module. Pretty easy to disconnect the ABS and see if it starts working again.

The module is discontinued anyway, besides being a half-assed setup to begin with. I pulled mine and deleted it all.

If the abs is taking down the signal, it may kill the speedo. The vss signal goes to the DRAC and then sends signals to the cluster, PCM and ABS module. Pretty easy to disconnect the ABS and see if it starts working again.

The module is discontinued anyway, besides being a half-assed setup to begin with. I pulled mine and deleted it all.

Thanks I did see that orileys sells the abs module

 

[ZooMad75]

I’d dump the abs on general principle before replacing it. It is not worth wasting money on to repair. Leaving it unplugged is the easiest thing to do if it is actually causing your speedo issue.

 

[ethanthatcher777]

I’d dump the abs on general principle before replacing it. It is not worth wasting money on to repair. Leaving it unplugged is the easiest thing to do if it is actually causing your speedo issue.

I tried unplugging it with no luck I replaced the drac with a custom one speedo only starts moving at 40 now instead of 50 put in another vss with no luck

 

[dyeager535]

If no change id try to get my hands on another speedometer, however, does cruise work? Is the ECM reporting correct vehicle speed? Need to make sure it's not a wire or connection issue elsewhere.

I tried unplugging it with no luck I replaced the drac with a custom one speedo only starts moving at 40 now instead of 50 put in another vss with no luck

 

[ethanthatcher777]

If no change id try to get my hands on another speedometer, however, does cruise work? Is the ECM reporting correct vehicle speed? Need to make sure it's not a wire or connection issue elsewhere.

I don't think I have cruise also abs code 10 keeps popping when I hit 40 which is supposedly caused by a bad brake switch or a open circuit so the abs module is getting signal from the vss

 

[dyeager535]

I don't think I have cruise also abs code 10 keeps popping when I hit 40 which is supposedly caused by a bad brake switch or a open circuit so the abs module is getting signal from the vss

I'd want to see what the ECM is getting for a speed signal. It's pretty unlikely that everything after the DRAC is messed up, since they all use separate wires from the DRAC IIRC. ECM, cruise, ABS, Speedo, all are fed from different pins on the DRAC.

I'd expect something wrong with the wires between the VSS and DRAC if the ECM isn't seeing the speed accurately. That's a "straight" digital output, unlike the speedometer that could have mechanical issues with how it's driven, powered, grounded, etc.

Your problem doesn't sound like a complete failure of something, but the speed reported to the ECM should be indicative.

 

[ethanthatcher777]

I'd want to see what the ECM is getting for a speed signal. It's pretty unlikely that everything after the DRAC is messed up, since they all use separate wires from the DRAC IIRC. ECM, cruise, ABS, Speedo, all are fed from different pins on the DRAC.

I'd expect something wrong with the wires between the VSS and DRAC if the ECM isn't seeing the speed accurately. That's a "straight" digital output, unlike the speedometer that could have mechanical issues with how it's driven, powered, grounded, etc.

Your problem doesn't sound like a complete failure of something, but the speed reported to the ECM should be indicative.

I'm starting to believe it could be a bad cluster because the abs knows I am going 40 weird thing is that odo and trip doesn't move but speedo does after a certain speed

 

[dyeager535]

I'm starting to believe it could be a bad cluster because the abs knows I am going 40 weird thing is that odo and trip doesn't move but speedo does after a certain speed

That's why seeing what the ECM is getting matters. If it's just the speedometer with issues then wiring to it, connections, or speedometer itself.

 

[ethanthatcher777]

That's why seeing what the ECM is getting matters. If it's just the speedometer with issues then wiring to it, connections, or speedometer itself.

Ecm is getting signal but supposedly there is a vssb and a drac is that true? I thought the drac was the only one it's either that or the cluster

 

[1-ton]

You odometer may not be working because it has a step motor that has gone bad.

 

[ZooMad75]

Ecm is getting signal but supposedly there is a vssb and a drac is that true? I thought the drac was the only one it's either that or the cluster

A drac and a vssb are the same thing. In the squarebody trucks they were called drac. The later trucks used a vssb or vehicle speed sensor buffer. Same thing.


What’s important here is how the vss signal is shared. The vss signal goes to the Drac. From there the signal is sent on separate circuits to the ecm, abs and instrument cluster.

This is how you can have a vss value in the ecm and abs modules and nothing on the speedo.

The fact that the speedo works above a certain speed and the odometer is dead would lead me to a cluster. If the circuit was corrupted it wouldn’t work at all.