Vehicle speed sensor question
Team Owner
Joined: May 2001
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From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Not sure why you would be referencing the T-56 transmission as the Corvette's VSS is mounted to the differential and not the transmission, but according to the service manual:
Speedometer
"The IPC receives a 4000 pulse-per-mile Vehicle Speed Sensor (VSS) input over a dedicated input from the PCM. The PCM is responsible for processing the VSS data and sending it to the IPC."
HTH
Speedometer
"The IPC receives a 4000 pulse-per-mile Vehicle Speed Sensor (VSS) input over a dedicated input from the PCM. The PCM is responsible for processing the VSS data and sending it to the IPC."
HTH
Thread Starter
Pro
Joined: Mar 2002
Posts: 559
Likes: 0
From: Guelph Ontario
Thanks, I realize the sensor is mounted in the diff. I just thought they shared the same sensor as the T56 in a Camaro since the corvette tranny is basically a T56 ( correct? ). Are you sure this is the PPM for a manual trans? Is it the same as a automatic? If not, what is the PPM of an automatic?
Im trying to troubleshoot a resto-mod. Its a 55 chev with an LT5 and and 98 vette suspension. The motor will not engage the secondaries because it thinks the car is doing 250+ MPH even though its only doing about 60.
Its driving us crazy!!
Im trying to troubleshoot a resto-mod. Its a 55 chev with an LT5 and and 98 vette suspension. The motor will not engage the secondaries because it thinks the car is doing 250+ MPH even though its only doing about 60.
Its driving us crazy!!
Thread Starter
Pro
Joined: Mar 2002
Posts: 559
Likes: 0
From: Guelph Ontario
Not sure why you would be referencing the T-56 transmission as the Corvette's VSS is mounted to the differential and not the transmission, but according to the service manual:
Speedometer
"The IPC receives a 4000 pulse-per-mile Vehicle Speed Sensor (VSS) input over a dedicated input from the PCM. The PCM is responsible for processing the VSS data and sending it to the IPC."
HTH
Speedometer
"The IPC receives a 4000 pulse-per-mile Vehicle Speed Sensor (VSS) input over a dedicated input from the PCM. The PCM is responsible for processing the VSS data and sending it to the IPC."
HTH
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
Thanks, I realize the sensor is mounted in the diff. I just thought they shared the same sensor as the T56 in a Camaro since the corvette tranny is basically a T56 ( correct? ). Are you sure this is the PPM for a manual trans? Is it the same as a automatic? If not, what is the PPM of an automatic?
Im trying to troubleshoot a resto-mod. Its a 55 chev with an LT5 and and 98 vette suspension. The motor will not engage the secondaries because it thinks the car is doing 250+ MPH even though its only doing about 60.
Its driving us crazy!!
Im trying to troubleshoot a resto-mod. Its a 55 chev with an LT5 and and 98 vette suspension. The motor will not engage the secondaries because it thinks the car is doing 250+ MPH even though its only doing about 60.
Its driving us crazy!!
The Vehicle Speed Sensor (VSS) is located in the differential, and reads the speed at which the right hand axle is turning. The PCM "knows" the tire size ... so the PCM is responsible for actually "calculating" vehicle speed ..... if the VSS reports one revolution of the axle in one minute .... and the PCM is programmed to know that the tire size means that one revolution of the tire is (I'm exagerrating to make a point) equal to one mile ... then the PCM says "we covered one mile in one minute ..... that's 60 miles in 60 minutes .... tell the other systems on the car we are doing 60 MPH"
I suspect you need to either play with tire sizes in the PCM ... or how many pulses it expects for each turn of the axle ...... can't see what other parameters would mess you up ....
Good luck .....
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
The sensor itself is the same for the C5 A4 or MM6 and the GM part number is: 12369458 and since the reluctor wheel on the ring gear comes with the gear and is not serviced separately I assume it to be the same too. Not positive on that point though.
The VSS signal is sent straight to the PCM, which in turn sends this info to the IPC. I'm not sure if the PCM program info is where the correct info (as far as gear ratio in the diff) is determined but I would think it would be.
As far as IPC it stands for Instrument Panel Cluster.
HTH
The VSS signal is sent straight to the PCM, which in turn sends this info to the IPC. I'm not sure if the PCM program info is where the correct info (as far as gear ratio in the diff) is determined but I would think it would be.
As far as IPC it stands for Instrument Panel Cluster.
HTH
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
My stock M6 tune, the VSS pulses per mile is set at 31027.3.
The IPC receives a constant 4000 pulse/mile input from the PCM. That is different than the VSS output pulse (which is adjustable).
The IPC receives a constant 4000 pulse/mile input from the PCM. That is different than the VSS output pulse (which is adjustable).
Last edited by Y2Kvert4me; May 9, 2008 at 09:08 PM. Reason: added picture
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Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Question: Is the info in the PCM modifiable with a Tech II? I assume it would be. BTW, I did notice that the '97 and '98 each show a different (and only one is shown for each) PCM.
Another question I would have is what instrument cluster/speedo is being used?
Edit. Just saw your edit re: adjustability.
Last edited by LoneStarFRC; May 9, 2008 at 09:19 PM.
