Are miles stored in the PCM or in the gauge Cluster?
05-08-2010, 09:20 PM
#1
Are miles stored in the PCM or in the gauge Cluster? I bought a nice 01' Z-28 a few months ago that has only 38K miles on the clock.
If somebody in the past had a different cluster and then put this one back in as I have heard of other people doing would it work with these cars?
Either way it is a great car, but it has always been in the back of my mind.
If somebody in the past had a different cluster and then put this one back in as I have heard of other people doing would it work with these cars?
Either way it is a great car, but it has always been in the back of my mind.
05-10-2010, 04:16 PM
#3
That is what I was afraid of.
A friend at work told me about changing a cluster on a Caviler and he said the OD went right back to where it was with the old cluster, it just got my hopes up.
I wonder how many people pay extra for 'low mileage' cars and get duped by this?
A friend at work told me about changing a cluster on a Caviler and he said the OD went right back to where it was with the old cluster, it just got my hopes up.
I wonder how many people pay extra for 'low mileage' cars and get duped by this?
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LOCALOUTLAW (07-03-2019)
05-13-2010, 05:01 PM
#6
The mileage is stored in the Cluster AND in the PCM.
Naturally, what we 'see' is what is inside the cluster, but mileage can be read from the PCM also.
When a cluster is swapped, there is a procedure to be run from the GM scanner to sync the replacement cluster to the PCM, which will copy the mileage from the PCM to the cluster. Among other things such as airbag communications, etc.
But, if the battery was disconnected before the re-sync process, then that data is lost. All you'll have then is the cluster mileage.
Naturally, what we 'see' is what is inside the cluster, but mileage can be read from the PCM also.
When a cluster is swapped, there is a procedure to be run from the GM scanner to sync the replacement cluster to the PCM, which will copy the mileage from the PCM to the cluster. Among other things such as airbag communications, etc.
But, if the battery was disconnected before the re-sync process, then that data is lost. All you'll have then is the cluster mileage.
05-13-2010, 10:59 PM
#7
The mileage is stored in the Cluster AND in the PCM.
Naturally, what we 'see' is what is inside the cluster, but mileage can be read from the PCM also.
When a cluster is swapped, there is a procedure to be run from the GM scanner to sync the replacement cluster to the PCM, which will copy the mileage from the PCM to the cluster. Among other things such as airbag communications, etc.
But, if the battery was disconnected before the re-sync process, then that data is lost. All you'll have then is the cluster mileage.
Naturally, what we 'see' is what is inside the cluster, but mileage can be read from the PCM also.
When a cluster is swapped, there is a procedure to be run from the GM scanner to sync the replacement cluster to the PCM, which will copy the mileage from the PCM to the cluster. Among other things such as airbag communications, etc.
But, if the battery was disconnected before the re-sync process, then that data is lost. All you'll have then is the cluster mileage.
Can you produce any GM documentaion that says this? Since GM dealers send replacement speedometers to a certified shop to get the mileage set on them and the vehicle nor the PCM is ever involved.
Here is the instructions from the service manual concerning installing a replacement dash cluster
Instrument Panel Cluster (IPC) Programming/Synchronization
When installing a new Instrument Panel Cluster (IPC) it must be synchronized to the inflatable restraint sensing and diagnostic (SDM) module. In order to synchronize the new cluster, using a scan tool, perform the following steps:
Under Instrument Panel Cluster select the Special Functions option.
Select the Synchronize IPC and SIR option.
Then select yes or no. By selecting yes the IPC and SIR modules will synchronize.
When the procedure is completed successfully the scan tool will display Module synchronization is complete.
Notice no where does it say it will update the mileage
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05-13-2010, 11:23 PM
#8
WRONG....only the cluster stores mileage.
Nope.
When I decided to get the Granitelli 200mph speedo for my 1998 T/A back in 2002....I also decided that I wanted to keep my original cluster. So I called every GM dealer within 100 miles of me and asked this: Hello, I'm about to buy a used 1999 T/A and I want to know if I can bring it to you and have the mileage checked because I don't believe what the seller is telling me. He changed the cluster a few months ago but I'd like you to read the mileage from the PCM to see what the real mileage is.
They all said it can't be done....that the only mileage a scanner/computer will read is whatever is showing on the cluster readout.
SO....I then called a dealership out of state to buy the new cluster. WHY....because I knew if I bought it locally they would ask me to bring in my cluster so they can see the mileage, then program that mileage onto the new cluster. I figured since it was an out of state dealership that they would just take my word for it. NOPE....they said I had to send them my original cluster to them so they can pull the mileage off of it. WELL....hahaha....thinking fast on the phone.....I told this out of state dealership that I removed the old cluster, couldn't get it to work and I tossed it in the garbage and its gone. There were like, "Uh, ok then, just tell me what your mileage is then and we'll program that in and send it to you."
Of course, being a law abiding citizen I told them the correct mileage...lol
I got it about 1 week later and sent it to Granitelli for the 200mph speedo kit with THAT mileage on there showing on the readout, they did their thing and sent it back to me.
I still have my original cluster, which for awhile would go in when I went on long trips. But I don't bother any more doing that since my car has around 170,000 total miles.
.
Naturally, what we 'see' is what is inside the cluster, but mileage can be read from the PCM also.
When I decided to get the Granitelli 200mph speedo for my 1998 T/A back in 2002....I also decided that I wanted to keep my original cluster. So I called every GM dealer within 100 miles of me and asked this: Hello, I'm about to buy a used 1999 T/A and I want to know if I can bring it to you and have the mileage checked because I don't believe what the seller is telling me. He changed the cluster a few months ago but I'd like you to read the mileage from the PCM to see what the real mileage is.
They all said it can't be done....that the only mileage a scanner/computer will read is whatever is showing on the cluster readout.
SO....I then called a dealership out of state to buy the new cluster. WHY....because I knew if I bought it locally they would ask me to bring in my cluster so they can see the mileage, then program that mileage onto the new cluster. I figured since it was an out of state dealership that they would just take my word for it. NOPE....they said I had to send them my original cluster to them so they can pull the mileage off of it. WELL....hahaha....thinking fast on the phone.....I told this out of state dealership that I removed the old cluster, couldn't get it to work and I tossed it in the garbage and its gone. There were like, "Uh, ok then, just tell me what your mileage is then and we'll program that in and send it to you."
Of course, being a law abiding citizen I told them the correct mileage...lol
I got it about 1 week later and sent it to Granitelli for the 200mph speedo kit with THAT mileage on there showing on the readout, they did their thing and sent it back to me.
I still have my original cluster, which for awhile would go in when I went on long trips. But I don't bother any more doing that since my car has around 170,000 total miles.
.
05-15-2010, 12:42 PM
#10
The mileage is stored in the PCM, but it is soft and relies on the IPC to update it. If you remove the VSS from the IPC the mileage will still count up in the PCM, but as soon as the IPC mileage changes the PCM updates to that mileage. I have software to reprogram the IPC at any mileage. At the dealership we now update mileage on some IPC's when installing them. This procedure has only been out maybe 2 years. Before that the IPC's came programed with the mileage at the time the IPC was ordered. If you look around on the internet you can find software for IPC's.
05-15-2010, 01:57 PM
#11
The mileage is stored in the PCM, but it is soft and relies on the IPC to update it. If you remove the VSS from the IPC the mileage will still count up in the PCM, but as soon as the IPC mileage changes the PCM updates to that mileage. I have software to reprogram the IPC at any mileage. At the dealership we now update mileage on some IPC's when installing them. This procedure has only been out maybe 2 years. Before that the IPC's came programed with the mileage at the time the IPC was ordered. If you look around on the internet you can find software for IPC's.
05-15-2010, 02:06 PM
#12
A lot of the newer PCM''s also store, the number of times they were flashed and what OS's were put on them, but it wasn't always that way. I'll wait, but I don't think you'll ever produce any GM documentation, showing how to read the mileage from the (12200411) PCM in the 2001 F-bodies. So until you do, its not true
