C5/C6 ABS sensor

[andrewb70]

Does anyone know how many pulses per revolution a stock C5 ABS sensor is?

Andrew

[andrewb70]

I found this picture:



Counting the teeth it looks like the wheel might have 45 or 48 teeth. Does anyone know for sure?

Andrew

[Rhino]

You beat me to it. I had an old pair of c5 hubs in the garage and decided to donate one to science. There are 48.

[andrewb70]

Thanks for the confirmation!

Andrew

[Rhino]

No problem. For the past few years I've been pondering the ability to use the 4th gen F-body system in my '68. At the time I didn't have any spares so I wasn't able to confirm. I may just have to start up that project again.

[andrewb70]

No problem. For the past few years I've been pondering the ability to use the 4th gen F-body system in my '68. At the time I didn't have any spares so I wasn't able to confirm. I may just have to start up that project again.

I am very interested in this as well, but this is for something else. For reasons that are mostly irrelevant to this thread, I removed the speedo gear out of my Richmond 6 speed transmission, and thus, lost my speed. Do you see any reason why the ABS sensor can't be used to feed a signal to an Autometer programmable speedo?

Also, can I feed this signal into my ECU? It is a E67 from the GMPP LS7 harness kit. The GM VSS signal is either 17 or 40 pulses, what would happen if it saw 48?

Andrew

[Rhino]

Even with the discrepancy of 40 vs 48 pulses you'd be looking at a speed error of close to 17%. Depending on what your ECU is using the speed for this may be "close enough". You may be able to resolve this error by modifying the rear end ratio in your tune, but that may have outside impact as well.
In the past I've built signal conditioners to resolve errors such as this. There are now plenty of commercial options on the market. On my car I'm currently using a Dakota Digital SGI-5. If I recall I paid about $80 for it. I'm using it to take the 17 pulse VSS and convert this to a 2000 PPM signal for my cruise control.

I can't see a reason it wouldn't work. This is nothing more than a standard hall effect sensor.

[andrewb70]

Even with the discrepancy of 40 vs 48 pulses you'd be looking at a speed error of close to 17%. Depending on what your ECU is using the speed for this may be "close enough". You may be able to resolve this error by modifying the rear end ratio in your tune, but that may have outside impact as well.
In the past I've built signal conditioners to resolve errors such as this. There are now plenty of commercial options on the market. On my car I'm currently using a Dakota Digital SGI-5. If I recall I paid about $80 for it. I'm using it to take the 17 pulse VSS and convert this to a 2000 PPM signal for my cruise control.

I can't see a reason it wouldn't work. This is nothing more than a standard hall effect sensor.

That's what I figured. Also, can't the ECU be programmed to tell it how many pulses per revolution to expect?

On the ABS sensor itself, how do I tell which wire is the hi signal and which is the low signal?

Andrew

[Rhino]

Unfortunately I'm not sure if that can be reprogrammed. I'm pretty certain this is hard coded on most GM vehicles, not sure about GMPP PCM's. Did the setup come with software or does it require the use of HPT/EFI Live?

As far as the sensor is concerned: I don't think it would technically matter since hall effect sensors would generate an A/C voltage. Additionally, both wires appear to be black.

[andrewb70]

Unfortunately I'm not sure if that can be reprogrammed. I'm pretty certain this is hard coded on most GM vehicles, not sure about GMPP PCM's. Did the setup come with software or does it require the use of HPT/EFI Live?

As far as the sensor is concerned: I don't think it would technically matter since hall effect sensors would generate an A/C voltage. Additionally, both wires appear to be black.

There is no software, but it can be tuned with HPTuners or EFI Live.

On my ECU wiring diagram the wires are labeled VSS TOSS Hi Pos 2 and VSS TOSS Lo Pos 1. The wires are Purple/white and Lt. Green/Black, respectively. Like you said, maybe it doesn't matter?

Andrew

[Rhino]

If they're specifying a high and low wire I'd have to assume there's some difference. I tried looking up a wiring diagram, however the site I have access to apparently doesn't like any browser on Linux.
Looking at CorvetteForum it appears to be mixed on whether or not it makes a difference. They seem to mention an electrical writeup however no direct link is ever given. Once I get access to some wiring diagrams I'll post up what I find.

[andrewb70]

If they're specifying a high and low wire I'd have to assume there's some difference. I tried looking up a wiring diagram, however the site I have access to apparently doesn't like any browser on Linux.
Looking at CorvetteForum it appears to be mixed on whether or not it makes a difference. They seem to mention an electrical writeup however no direct link is ever given. Once I get access to some wiring diagrams I'll post up what I find.

Thank you! You've been a great help. I'll be able to have a working speedo again and maybe the ECU will be happier with a VSS signal. I hear it helps with low speed and coasting situations.

Andrew

[andrewb70]

Here is a link to the ECU installation instructions, so you can see what I am referencing:

http://www.chevroletperformance.com/...rol_System.pdf

Andrew

[Rhino]

I did find this: http://www.justanswer.com/chevy/6spr...l-service.html
It seems to indicate that the sensors are wired differently depending on wheel position.

If you take a look at the sensor plug itself, on the side with the clip, you'll find the plugs marked A and B. On the sensor I'm looking at A is the right side plug.

Adding this all up, considering the mix of high/low values in the diagram the sensor doesn't care how it's wired. What would still need to be verified is if the VSS output is similar.

[andrewb70]

I did find this: http://www.justanswer.com/chevy/6spr...l-service.html
It seems to indicate that the sensors are wired differently depending on wheel position.

If you take a look at the sensor plug itself, on the side with the clip, you'll find the plugs marked A and B. On the sensor I'm looking at A is the right side plug.

Adding this all up, considering the mix of high/low values in the diagram the sensor doesn't care how it's wired. What would still need to be verified is if the VSS output is similar.

So which one is HI and which one is Lo? LOL

Andrew

[Rhino]

That's the funny thing, looking at the diagram there (http://ww2.justanswer.com/uploads/cr...184928_abs.pdf) it shows the polarity as follows:

Left Front: A low, B signal
Left Rear: A signal, B low
Right Front: A signal, B low
Right Rear: A signal, B low



Since the left and right sides share a common part number the sensor itself has to be identical, however the chassis side harness lists reversed polarity for the two front corners. I'd conclude that it really doesn't matter how the sensor is wired.

[andrewb70]

That's the funny thing, looking at the diagram there (http://ww2.justanswer.com/uploads/cr...184928_abs.pdf) it shows the polarity as follows:

Left Front: A low, B signal
Left Rear: A signal, B low
Right Front: A signal, B low
Right Rear: A signal, B low

Since the left and right sides share a common part number the sensor itself has to be identical, however the chassis side harness lists reversed polarity for the two front corners. I'd conclude that it really doesn't matter how the sensor is wired.

Thanks again. I really appreciate the help. I will wire pin A for Hi and B for Lo, if it matters, I have a 50/50 shot of getting it right...LOL

Andrew

[fast98]

You can use the hub for the vss and reprogram the PCM for it but wouldn't it have been easier to just get the autometer GPS unit? Just thinking out loud here.

[andrewb70]

You can use the hub for the vss and reprogram the PCM for it but wouldn't it have been easier to just get the autometer GPS unit? Just thinking out loud here.

Yes, this would be easier, but it would also be more expensive. LOL

Andrew

[andrewb70]

So I picked one wire off the ABS sensor and I hooked it up to the Hi input on the ECU and also split it off to my speedo. The speedo is still not working and I can't really tell if the ECU is acting any differently.

I am thinking that I need to feed both the Hi and the Low to the ECU. Any thoughts on this and how I might wire in my Autometer speedo?

Andrew