Update 2/October/2025

You no longer need to manually correct the checksum of the GM calibration files. You can automatically correct the checksum of modified GM calibration files online using this checksum tool, which was created by a CameraLoops member.

The online checksum tool can be accessed from the website's top menu, under the "Tools & Games" button, or via the following web link. GM Online Checksum Calculator

Massive thanks to ECU-Online.com

In this tutorial, I will explain in steps how to correct the checksum after editing a GM module calibration file.

This process illustrates correcting the checksum for the first four bytes.

 

It's beneficial to read up on these other tutorials to familiarise yourself with GM's calibration files concept if you're new. 

 

 

Tools you will need.

 Hex Editor Neo

 

 

Step 1.

Open the calibration file in Neo and edit your file.

Set Predefined Layouts as Expert User Layout.

 

Step 2.

Select all the codes in the calibration file except the first four bytes/code.

 

Step 3.

At the bottom of Neo click Checksum.

 

Step 4.

In Neo's checksum window, change the option: Whole document to Selection only.

 

Step 5.

Select Sum of Big-Endian 16-bit value 

 

Step 6.

Click the  Refresh button.

 

Step 7.

Copy the last 4 digits, which is: 9730 

 

Step 8.

Convert 9730 into Binary code, then copy paste the binary code in a text editor.

 

Step 9.

Now you need to create a reverse copy of the binary code: 1001011100110000, see the example below.

 

Step 10.

Convert the reverse binary code 0110100011001111 into hexadecimal code, which equals to 68cf 

 

Step 11.

Now you need to add 1 to the hexadecimal code, which looks like this 68cf+1=

Use this online calculator to do the calculation.

68cf+1=68d0

 

Step 12.

Now you have 68d0

Replace the first four unselected bytes/code in the calibration file with 68d0.

 

Step 13.

The checksum has been corrected.

Save the calibration file and program your calibration package to the module using GM DPS.

 

 

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Great tutorial Troy.

Thank you.

Step 9 

Can you explain how I reversed it? 

2 hours ago, danial said:

Step 9 

Can you explain how I reversed it? 

Check and decipher the attached before and after photo.

Hi I can't figure out how to do this in Step 9

1 hour ago, Shavkat said:

Hi I can't figure out how to do this in Step 9

 

 

Yep, correcting the checksum can be a bit confusing.

 

In step 9 reverse the binary code.

Example: 

The binary code that needs to be reversed is: 1001011100110000

 

To reverse it.

Paste the code in a text editor like this, then type the opposite number underneath the original code 

1001011100110000

 

Change the 0 into 1 and the 1 into 0, in the same order as the original binary code.

Example the original binary code begins with 1001 the reverse code will begin with 0110

1001011100110000 Original code

011010011001111 reversed code

 

Spot the difference in the example photo below. 

In the reverse code, all the digits 1 was converted into the digit 0, and all the digits 0, was converted into the digit 1

 

If you still don't get it, let me know.

 

?

16 minutes ago, Troy said:

 

 

Yep, correcting the checksum can be a bit confusing.

 

In step 9 reverse the binary code.

Example: 

The binary code that needs to be reversed is: 1001011100110000

 

To reverse it.

Paste the code in a text editor like this, then type the opposite number underneath the original code 

1001011100110000

 

Then change the 0 into 1 and the 1 into 0, in the same order as the original binary code.

Example the original binary code begins with 1001 the reverse code will begin with 0110

1001011100110000 Original code

011010011001111 reversed code

 

Spot the difference in the example photo below. 

In the reverse code, all the digits, 1 was converted into the digit 0, and all the digits 0 was converted into the digit 1

 

If you still don't get it, let me know.

 

Thanks now I understand

I know this is a little off this topic. But in DPS get controller info. It asks for a ECU Aderess/ID$ ?  I found that 11 is the ECM But I was trying to find others like Bcm, FPCM, ABS

15 hours ago, WWEILER said:

I know this is a little off this topic. But in DPS get controller info. It asks for a ECU Aderess/ID$ ?  I found that 11 is the ECM But I was trying to find others like Bcm, FPCM, ABS

You can use gds2 to find out the ecu ID for any given module. In gds2, select the module and select ‘module identification’, the ecu ID will display on that page. 
 

ECU address ID Diagnostic pin

HMI: 8F, PIN: 6 and 14

IPC: 60, PIN 1

BCM: 40, PIN: 6 and 14

Radio: 80, PIN: 1

ECU: 11, PIN: 6 and 14

 

From insignia. 

High Speed HS-CAN Bus 

>> Base Mapping Matrix:

>> ECU 0x11 on HS-CAN (ReqCANId: 0x000007E0, RspCANId: 0x000007E8) ECM

>> ECU 0x8F on HS-CAN (ReqCANId: 0x00000252, RspCANId: 0x00000652) HMI

>> ECU 0x18 on HS-CAN (ReqCANId: 0x000007E2, RspCANId: 0x000007EA)

>> ECU 0x2B on HS-CAN (ReqCANId: 0x00000254, RspCANId: 0x00000654)

>> ECU 0x28 on HS-CAN (ReqCANId: 0x00000243, RspCANId: 0x00000643) Electronic Brake Control Module 

>> ECU 0x72 on HS-CAN (ReqCANId: 0x00000249, RspCANId: 0x00000649) K26 Headlamp Control Module

>> ECU 0x31 on HS-CAN (ReqCANId: 0x00000242, RspCANId: 0x00000642) K43 Power Steering Control Module 

>> ECU 0x40 on HS-CAN (ReqCANId: 0x00000241, RspCANId: 0x00000641) BCM

 

 

Low Speed LS-CAN Bus 

>> Base Mapping Matrix:

>> ECU 0x60 on LS-CAN (ReqCANId: 0x0000024C, RspCANId: 0x0000064C) IPC

>> ECU 0x66 on LS-CAN (ReqCANId: 0x00000246, RspCANId: 0x00000646)  A22 Radio Controls 

>> ECU 0xAF on LS-CAN (ReqCANId: 0x00000242, RspCANId: 0x00000642)

>> ECU 0x80 on LS-CAN (ReqCANId: 0x00000244, RspCANId: 0x00000644) RADIO

>> ECU 0x58 on LS-CAN (ReqCANId: 0x00000247, RspCANId: 0x00000647)

>> ECU 0x68 on LS-CAN (ReqCANId: 0x00000248, RspCANId: 0x00000648) A26 HVAC CONTROLS 

>> ECU 0xA4 on LS-CAN (ReqCANId: 0x0000024F, RspCANId: 0x0000064F) K39 Liftgate control module

>> ECU 0x99 on LS-CAN (ReqCANId: 0x00000251, RspCANId: 0x00000651) maybe hvac

>> ECU 0x8D on LS-CAN (ReqCANId: 0x00000252, RspCANId: 0x00000652)

>> ECU 0x75 on LS-CAN (ReqCANId: 0x00000253, RspCANId: 0x00000653) K101 Trailer Interface Control Module 

>> ECU 0xBB on LS-CAN (ReqCANId: 0x00000259, RspCANId: 0x00000659) K182 Parking Assist Control Module

>> ECU 0xC2 on LS-CAN (ReqCANId: 0x0000025C, RspCANId: 0x0000065C) K60 Steering Column Lock Control Module

>> ECU 0xA8 on LS-CAN (ReqCANId: 0x0000025D, RspCANId: 0x0000065D) Front seat Heating/venting/cooling/memory/ control module

>> ECU 0x73 on LS-CAN (ReqCANId: 0x0000025F, RspCANId: 0x0000065F) K82 Automatic Headlamp High Beam control Module 

>> ECU 0x40 on LS-CAN (ReqCANId: 0x00000241, RspCANId: 0x00000641)  BCM

B219 Steering Wheel angle sensor address 34

B9 obstacle 

 

 

 

Hello Troy. 

I crosschecked your calculations towards some of my saved cache files. I could be mistaken but all steps except 11 are necessary. When adding the one the checksum becomes wrong. Am I mistaken or is there a risk that the checksum calculation is differing between our versions?

8 minutes ago, Anders Johansson said:

Hello Troy. 

I crosschecked your calculations towards some of my saved cache files. I could be mistaken but all steps except 11 are necessary. When adding the one the checksum becomes wrong. Am I mistaken or is there a risk that the checksum calculation is differing between our versions?

Not sure. I’ll have to cross check it later. 

Hello, THANK YOU for your tuto Troy. ;o)

Here is an easier way to do steps 8 through 11.  The checksum in the GM calibration files is the 2s complement of the 16-bit sum.  You can use a 2s complement calculator like this: 

1's & 2's Complement Calculator

NCALCULATORS.COM

---

1's & 2's complement calculator is an online digital computation tool to find the one's & two's...

 

 

Set input type to hex.   Using the example from step 7, enter 9730.   Click the big blue Convert button on the right.

 

2s Complement Binary will be 110100011010000.   Convert that binary back to hex using your favorite tool. 

 

110100011010000 = 68D0

 

 

Thanks Troy I will have to hoopup my GDS2 and check that out?

On 8/18/2021 at 1:33 AM, HMI_Guy said:

Here is an easier way to do steps 8 through 11.  The checksum in the GM calibration files is the 2s complement of the 16-bit sum.  You can use a 2s complement calculator like this: 

1's & 2's Complement Calculator

NCALCULATORS.COM

---

1's & 2's complement calculator is an online digital computation tool to find the one's & two's...

 

 

Set input type to hex.   Using the example from step 7, enter 9730.   Click the big blue Convert button on the right.

 

2s Complement Binary will be 110100011010000.   Convert that binary back to hex using your favorite tool. 

 

110100011010000 = 68D0

 

 

Great info, thanks 

First, many many thanks, but this did not work on any of the files i tried on
2008 IPC system file

2019 BCM Automatic lighting file

also 2013 BCM System calibration file

when i check the original value of the file to test the calculation, some files it is close to your calculation, some are not near the calculated value

 

btw non of the above files have been solved yet

Hi Troy, you have some unnecessary steps there. Why are you switching from Hex to Binary?

On 8/6/2021 at 2:57 PM, Troy said:

Change the 0 into 1 and the 1 into 0, in the same order as the original binary code.

Example the original binary code begins with 1001 the reverse code will begin with 0110

1001011100110000 Original code

011010011001111 reversed code

 

68cf  XOR FFFF = 9730 

 

XOR function is probably built into your calc and its also built into windows calculator when in programmer mode

 

Not the best contribution but sharing what I have

 

Does anyone know Correct Checksum for calibration files of ECM, EPS, TCM... boxes that can guide everyone?

I have a question. when is necessary do this correction?
before create a SPAT file to load it whit DPS? for example, to load a calibration file into a BCM from another VIN download?

I means, only correct the Checksum in the files would i change. correct? if the BCM has 20 files, and i want to change 2. correct the cheksum in this 2 files. In the other 18, no change the checksum.

I think. After Calculate Checksum. We need calculate CVN of that calibration file(edited) and then need to edit calibration Utility or BCM OS, but I don't know how do.

Perhaps it's worth to mention that this checksum calculation method doesn't work for all type of calibration files such as the EBCM or TCM.

 

On 8/12/2021 at 11:51 AM, Troy said:

You can use gds2 to find out the ecu ID for any given module. In gds2, select the module and select ‘module identification’, the ecu ID will display on that page. 
 

ECU address ID Diagnostic pin

HMI: 8F, PIN: 6 and 14

IPC: 60, PIN 1

BCM: 40, PIN: 6 and 14

Radio: 80, PIN: 1

ECU: 11, PIN: 6 and 14

 

From insignia. 

High Speed HS-CAN Bus 

>> Base Mapping Matrix:

>> ECU 0x11 on HS-CAN (ReqCANId: 0x000007E0, RspCANId: 0x000007E8) ECM

>> ECU 0x8F on HS-CAN (ReqCANId: 0x00000252, RspCANId: 0x00000652) HMI

>> ECU 0x18 on HS-CAN (ReqCANId: 0x000007E2, RspCANId: 0x000007EA)

>> ECU 0x2B on HS-CAN (ReqCANId: 0x00000254, RspCANId: 0x00000654)

>> ECU 0x28 on HS-CAN (ReqCANId: 0x00000243, RspCANId: 0x00000643) Electronic Brake Control Module 

>> ECU 0x72 on HS-CAN (ReqCANId: 0x00000249, RspCANId: 0x00000649) K26 Headlamp Control Module

>> ECU 0x31 on HS-CAN (ReqCANId: 0x00000242, RspCANId: 0x00000642) K43 Power Steering Control Module 

>> ECU 0x40 on HS-CAN (ReqCANId: 0x00000241, RspCANId: 0x00000641) BCM

 

 

Low Speed LS-CAN Bus 

>> Base Mapping Matrix:

>> ECU 0x60 on LS-CAN (ReqCANId: 0x0000024C, RspCANId: 0x0000064C) IPC

>> ECU 0x66 on LS-CAN (ReqCANId: 0x00000246, RspCANId: 0x00000646)  A22 Radio Controls 

>> ECU 0xAF on LS-CAN (ReqCANId: 0x00000242, RspCANId: 0x00000642)

>> ECU 0x80 on LS-CAN (ReqCANId: 0x00000244, RspCANId: 0x00000644) RADIO

>> ECU 0x58 on LS-CAN (ReqCANId: 0x00000247, RspCANId: 0x00000647)

>> ECU 0x68 on LS-CAN (ReqCANId: 0x00000248, RspCANId: 0x00000648) A26 HVAC CONTROLS 

>> ECU 0xA4 on LS-CAN (ReqCANId: 0x0000024F, RspCANId: 0x0000064F) K39 Liftgate control module

>> ECU 0x99 on LS-CAN (ReqCANId: 0x00000251, RspCANId: 0x00000651) maybe hvac

>> ECU 0x8D on LS-CAN (ReqCANId: 0x00000252, RspCANId: 0x00000652)

>> ECU 0x75 on LS-CAN (ReqCANId: 0x00000253, RspCANId: 0x00000653) K101 Trailer Interface Control Module 

>> ECU 0xBB on LS-CAN (ReqCANId: 0x00000259, RspCANId: 0x00000659) K182 Parking Assist Control Module

>> ECU 0xC2 on LS-CAN (ReqCANId: 0x0000025C, RspCANId: 0x0000065C) K60 Steering Column Lock Control Module

>> ECU 0xA8 on LS-CAN (ReqCANId: 0x0000025D, RspCANId: 0x0000065D) Front seat Heating/venting/cooling/memory/ control module

>> ECU 0x73 on LS-CAN (ReqCANId: 0x0000025F, RspCANId: 0x0000065F) K82 Automatic Headlamp High Beam control Module 

>> ECU 0x40 on LS-CAN (ReqCANId: 0x00000241, RspCANId: 0x00000641)  BCM

B219 Steering Wheel angle sensor address 34

B9 obstacle 

 

 

 

The module ID is also contained in the utility file that is in SPS Cache folder

On 1/10/2022 at 7:28 AM, Hero Tran said:

I think. After Calculate Checksum. We need calculate CVN of that calibration file(edited) and then need to edit calibration Utility or BCM OS, but I don't know how do.

You only need to calculate the CVN for the ECM and maybe the TCM

Nice info Mr Troy, but if I may offer some advice the windows Calculator has a Programmer mode that easily takes the last four of Big-Endian HEX checksum(highlight all bytes except the first two of .bin file) and if you go to Bitwise menu, you use NOT function and add 1 and there’s your new checksum