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I've notice you can't change the code for an e39
After a power cycle it goes back to its original code

mattyjf01 wrote:I've notice you can't change the code for an e39
After a power cycle it goes back to its original code

What I've found in the past, is if the ecu is blank (brand new) after an SPS it will allow a relink with Immo. However, it seems that it has to be reset and relinked with new code during the same key cycle.
I Usually reset, then SPS then relink while in car if I remember correctly.

Once they're reset (both E77 and E39) they're reset. They do still have the original code written until a relink to immo is done.

SPS doesn't care if its linked or not (generally speaking)

My experience anyway

disabled button is
- just an ecu immo code write

Waiting on a car to test them on

LangasLS wrote:Once they're reset (both E77 and E39) they're reset. They do still have the original code written until a relink to immo is done.

SPS doesn't care if its linked or not (generally speaking)

My experience anyway

Not quite right. Once they are reset... they are not reset.

Power off unit.. and they will then show as security linked.

This is becomes the normal for Global A/B vehicles. They do not save the new data to flash unless meeting certain criteria.

I'm talking pre Global A here. I've never had one that once its been reset show up as being married again.

I regularly looked up security codes for S/H ecu's and reset them on the bench prior to going onsite to link them back to peoples cars.

LangasLS wrote:I'm talking pre Global A here. I've never had one that once its been reset show up as being married again.

I regularly looked up security codes for S/H ecu's and reset them on the bench prior to going onsite to link them back to peoples cars.

Then you are referring only to things like E38's which will typically save to flash very quickly, some ECUs do not do this and hold the changes in RAM until enough time or changes have occurred that it saves to flash (Done to save the flash memory from being written too many times).

This is valid for some pre-global A ECUs but becomes common in global A and newer.

Believe it or not, Just my experiences after flashing hundreds of modules over the last decade!

Tazzi wrote:Not quite right. Once they are reset... they are not reset.

Power off unit.. and they will then show as security linked.

This is becomes the normal for Global A/B vehicles. They do not save the new data to flash unless meeting certain criteria.

Correct
E39 after a power loss is locked and has its original code.
What criteria is needed before it will save to flash?

mattyjf01 wrote:

Tazzi wrote:Not quite right. Once they are reset... they are not reset.

Power off unit.. and they will then show as security linked.

This is becomes the normal for Global A/B vehicles. They do not save the new data to flash unless meeting certain criteria.

Correct
E39 after a power loss is locked and has its original code.
What criteria is needed before it will save to flash?

Is there any other bytes that change other then the immo when reset compared to when relinked?
Any chance it flips a few bytes when a new immo is written rather then just delinked?

mattyjf01 wrote: Correct
E39 after a power loss is locked and has its original code.
What criteria is needed before it will save to flash?

Using global A/B as the example since its standardized and makes more sense to everyone, criteria can include things like:
1) Enough ram based variables changed so that it detects it requires saving to flash. This could include things like odometer readings. To maintain flash, ecu does not save this to flash on every single kilometer increase otherwise the flash memory would fail from too many writes.

2) After enough cycles/time passed for ignition on/off (keeping battery power on).

Personally I have been moving towards using my own custom bootloaders to write over the required sections to put them back to factory (new) settings and then security linking from there.

The above applies to preglobal A too, mainly anything that does not have an eeprom on board basically and uses an emulated eeprom in the CPU flash memory.