WinOLS Mastery: Map Identification & Editing: Checksum Correction
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Checksum Correction
02.51
| 00:00 | - One of the aspects that's critical when modifying the calibration of a factory ECU is that we need to be able to perform what's referred to as check sum correction. |
| 00:09 | This is an aspect that's often discussed, however there isn't a huge amount of information on what exactly this means or what the process involves. |
| 00:17 | Failing to correct the ECU's check sum will also leave you with a car that won't start so it's pretty vital to understand and get right. |
| 00:25 | The check sum is a value that is calculated based on the contents of a block of data within the ECU. |
| 00:31 | As there is a form of error checking to verify that the contents of the data that the ECU has read does in fact match the check sum. |
| 00:38 | You could think of it in very simple terms as the check sum equalling the total value of all of the bits of information within the ECU's memory. |
| 00:46 | This isn't totally accurate but it's a suitable analogy for our purposes. |
| 00:51 | Now if we go into a map and we change the value of some of the data, the original check sum will no longer match what the ECU has read. |
| 00:58 | This means the ECU knows that something isn't right. |
| 01:01 | Either the data has been altered, or it hasn't read that data correctly. |
| 01:06 | The ECU basically doesn't know what to do in this situation and to prevent the potential for damage to the engine, the car usually won't start. |
| 01:14 | To avoid this, once the relevant modifications have been made to your file, a new check sum needs to be calculated so that once again, the check sum matches what the ECU is seeing. |
| 01:25 | This keeps the ECU happy and we can get back to the process of tuning. |
| 01:29 | If we look back to the earlier days of WinOLS, check sum correction was a lot more challenging than it is these days and required a little more work from the tuner. |
| 01:38 | Currently the check sum correction is typically handled by the flash hardware you're using and is taken care of automatically in the background when you write the file to the ECU. |
| 01:48 | In the unlikely situation where you're using a hardware interface that's not capable of performing check sum correction, there are third party services that can provide this for you. |
| 01:58 | However we'd simply recommend ensuring the interface you choose can handle this. |
| 02:03 | A word of warning before we finish this module. |
| 02:05 | We do need to be mindful of changing the data that lies outside of the given check sum area. |
| 02:11 | OLS will let you know if you're doing this and it's something you should avoid as this can cause problems with the external check sum calculation on some tools. |
| 02:20 | Let's have a quick recap before we move on. |
| 02:22 | Remember that a check sum is simply a value that the ECU uses to ensure the integrity of the data the ECU has read. |
| 02:29 | Any time we make changes to the memory contents of the ECU, a new check sum value needs to be calculated so that this matches the memory contents. |
| 02:37 | If the check sum is incorrect, the engine typically won't start. |
| 02:40 | Fortunately the check sum correction is usually taken care of automatically by the hardware interface so you shouldn't need to be doing this manually. |
