Speedo Recalibration Issue

iminaquagmire · June 16, 2009

I went to the dealer today to get my speedo recalibrated for my 285's. They told me it could be up to a two hour job because they have to get a GM calibration for that specific size. Something about entering a "tach" or "link" calibration. They said if its not a stock size, they have to get a code from GM and if GM didn't have it, they would have to have them make one and send it. In my head I was hearing "BULLSH!T, BULLSH!T, BULLSH!T" because I know it can be done with a programmer in a matter of minutes. But then I thought about how the GMT-900 series is loaded with more computer crap than ever and got to wondering if maybe they were telling the truth. Does this sound legit or should I take it someplace that just has a programmer. I could get my Blackbear tune redone but I don't want to do that until I get new gears and wheels/tires which is now looking like next year as far as timeframe.

Jennabear · June 16, 2009

It actually is legit, as they have to get a VCI number. However, they should not charge you for two hours, as they are spending most of the time waiting for that number to come in. Your tire size shouldn't be too far off, however, if you are really concerned, you can get Justin to retune it for the tire size.

smattei14 · June 16, 2009

I just up graded my rim/tires...check out this site...it will allow you to see how off your speed is. I am .6 mph off...so i didn't think it was needed for me to get them recal. by the dealer.

http://www.miata.net/garage/tirecalc.html

scottmoyer · June 16, 2009

From what I was told, the reason they need the code from GM is so that GM can update their records for your VIN number. They are not thinking you have a tuned vehicle, so they update their records in case you need to have the PCM reflashed, the new tire size will be there. That was the deal I was told when I needed to have the computer recognize the steering wheel controls. Now if GM decides to flash my computer, that option is preprogrammed in for my VIN. The same holds true for stereo swaps too I think.

iminaquagmire · June 16, 2009

I have 285's in place of the stock 245's, so my speedo is 4.3mph off. It doesn't sound like much but that carries over to the odometer too. Looks like I'll be heading to the dealer. Thanks everybody.

Z45 · June 16, 2009

fyi

Identifying Aftermarket Non-GM Calibrations
By Blog Admin on February 1, 2009 7:17 PM | No Comments

For more details, refer to bulletins 08-06-04-033 (Gasoline Engines) and 08-06-04-006A (Diesel Engines).

General Motors is identifying an increasing number of engine, transmission and catalytic converter part failures that are the result of non GM - aftermarket engine and transmission control calibrations being used.

When alteration to the GM released engine or transmission control calibrations occurs, it subjects powertrain and driveline components (engine, transmission, transfer case, driveshaft and rear axle) to stresses that were not tested by General Motors. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy to cancel any remaining warranty coverage to the powertrain and driveline components, whenever the presence of a non-GM / aftermarket calibration is confirmed -- even if the non-GM control module calibration is subsequently removed.

Warranty coverage is based on the equipment and calibrations that were released on the vehicle at time of sale, or subsequently updated by GM. That's because GM testing and validation matches the calibration to a host of criteria that are essential to assure reliability, durability and emissions performance over the life of the warranty coverage and beyond. Stresses resulting from calibrations different than those tested and released by GM can damage or weaken components, leading to poor performance and or shortened life.

Additionally; non-GM-issued aftermarket engine control modifications often do not meet the same emissions performance standards as GM-issued calibrations. Depending on state statutes, individuals who install engine control module calibrations that put the vehicle outside the parameters of emissions certification standards may be subject to fines and / or penalties.

GM service bulletins 08-06-04-033 and 08-06-04-006 outline procedures to identify the presence of non-GM / aftermarket calibrations. GM recommends performing this check whenever a hard part failure is seen on internal engine or transmission components, or before an engine assembly or transmission assembly is being replaced under warranty. It is also recommended that the engine calibration verification procedure be performed whenever diagnostics indicate that catalytic converter replacement is indicated.

In February 2009, PQC will begin piloting a process to confirm the ECM calibration is GM-issued. Beginning in February, PQC will require a picture of the engine calibration verification screen, as outlined in the bulletin, before authorizing any V8 engine replacement (both Gas and Diesel). (fig. 19)

If a non-GM calibration is detected by the dealership, follow the procedures outlined in the bulletin. Once documentation of the non-GM calibration has been received, and verification has taken place through GM, the remaining powertrain and driveline warranty will be cancelled and noted in VISS, and the dealership will receive the following notification:

Based on information that has been received, please inform the customer that the Powertrain portion of the New Vehicle Warranty is no longer in effect for the engine, transmission, driveline and rear axle on VIN XXXXXXXXXXXXXXXXX, due to the presence of non-GM calibrations and / or equipment. The stresses resulting from the non-GM calibrations and / or equipment were not validated by GM and therefore cannot be warranted on any components that are subject to those stresses. Repairs to powertrain or driveline components that may currently require repair should not be covered under the terms of the new vehicle warranty. The warranty group has been advised of this information and VISS will be updated accordingly.

- Thanks to Jay Dankovich

handsomerob · June 17, 2009

Actually they shouldn't be able to program for that tire size, Tach will only give authorization for tire sizes that where available stock on that vehicle, in the case of trucks either 245's or 265's.

They need to do the tire size for the ecm/tcm calibration so that the engine and Tranny know how fast you are going and so the tranny will shift at the right time in the right RPM range.

Even going to a larger rim/tire size ie: 20" rims on the denali etc. they come from GM with an Auth code needed when calling Tach to get the right program loaded to your VIN#

I would be very interested to know if your dealership somehow performed this program for 285's because we have been told it's not possible by Tach on many occasions.

iminaquagmire · June 17, 2009

Soooo, I possibly cannot get a recalibration from GM? Did you just use the Hypertech or is yours off? Maybe I should send my modules back to Justin instead. I just don't have spares so my truck would have to sit.

As for that warranty nonsense, I think that's been posted enough. They will not check for a recalibration unless there is component failure, and even then I still don't see it happening unless I put a cage inside and cover it in sponsor stickers advertising abuse. I do not drive my truck like a racetruck and any component that fails will do so because it was poorly designed or placed in a vehicle with to much weight and power for it. If the engine blows, I'll rebuild it better, stronger, and to produce more power. If the Trans fails, I'll know its because it was a poor choice to put in the truck anyway. I fully expect to put a built one in when this one fails. If anything, the tune is holding everything together.