I just finished installing my GXP gauge cluster. The swap went well with the instructions given to me by leftd. The odometer is correct and all of the features work correctly as well. The problem is that the first time I took it out, to see if the speedometer was still correct, it felt like it was reading about 5mph high. I had my dad get his truck out and run with me at various speeds, all of which showed my speedometer reading 5 mph high as I suspected. Does anyone know why this would be? I am running the stock 17'* as well as what I believe is the stock tire size, 235/55/17. Does anyone have any suggestions or solutions to this problem? I will probably take it to the dealer tomorrow and see what the service manager has to say. I know him pretty well and he might reprogram/recalibrate it if that is what is needed.
Grant

Is your transmission the same gearing as the donor car?

Almost all GM'* for years have used 4000 pulses per mile which databus unknown...is probably the same in your case.

If you found it to be off..the dealer probably can't do much for you. Call Intense and get a speedo recalibrator. I think it'* 3 or 4 wires and done. Piece of cake and makes changing tire sizes later a snap.

OK, so I did some troubleshooting today. I removed the cluster and put the original GXP chip back in. It shows the incorrect mileage as I thought it would but when I drove it, the speedometer was correct. My chip=correct mileage, incorrect speedometer, GXP chip=incorrect mileage, correct speedometer. So with this new information, are there any suggestions on getting both the correct mileage and correct speedometer reading?
EDIT: I forgot to mention that when I installed the GXP chip the DIC started giving a low coolant warning. I checked my owners manual and I don't even think my car is supposed to show low/high coolant on the DIC.
Grant

That is true, there is not a low coolant level warning on the DIC.

So my car doesn't have the option of showing low coolant on the DIC but the GXP does have this option? Does this mean that my new cluster is searching for a coolant reading but there is no feedback to it so it just shows low coolant? I am going to try and clear the code on Monday. I'll have my fingers crossed with hopes that it doesn't return. Right now I am just going to leave the whole GXP cluster assembly in there, chip and all. As I said earlier it is showing the wrong mileage but I could send that out and reprogram it if I had to. I need to get rid of this LC light first though.
Grant

That'* exactly what I was thinking. If we had a schematic for a GXP instrument cluster we might be able to trick it into thinking that the coolant low warning is clear. The Instrument Panel Cluster (IPC) gets input from various components such as the PCM, DIM, EBCM, Windshield Washer System etc. This particular function (low coolant on GXP IPC) is probably actuated by contact closure or opening at a level switch on the rad. Just a guess, then the signal may go through another module & converted, then sent to the IPC to turn the coolant low warning light or LED on. The older Bonnevilles 92-95? I think had this feature, IIRC, it was actuated by level sensing switch on the radiator.

Thanks for the response. Leftd90 has done the swap and said he was showing the same warning, low coolant on the DIC. He said that it eventually went away. Can I expect mine to dissapear soon even though I have no sensor? I realize I am in a little bit of uncharted water here and there may be no clear answer.
Grant

Yeah, okay. That is very strange, but if it goes away & doesn't come back, all is good.

Interesting.. on the 92-99'* unplugging the sensor and leaving the circuit open would keep the light off.