Can WRITE ALL Erase Missing ECU Settings?

[johnroberts2k]

Hi everyone,

I have a Megane IV Phase 2 with a fairly recent DDT4All ECU database.

When I select [XFBPH2] - Renault Megane IV Ph2 and run an ECU scan, it only detects a handful of ECUs. A-IVI (Navigation), UPC and ECM are missing, and UCH/BCM only shows as a partial match (blue).

I previously enabled wireless CarPlay by manually selecting A-IVI 1.13, which worked fine.

However, I've now been advised to use A-IVI 2.7 for a HMI change I need to do for auto high beam feature, and this is where I'm concerned.

Comparing the HMI settings:

A-IVI 1.13 has settings missing from 2.7:

• TPMS_Autoloc_CF = Present
• TyrePressureUnit_CF = PSI
• CFG_RemoteEngineStart = RES not present
• CFG_DSI_Setting = Absent

A-IVI 2.7 also has additional settings not found in 1.13, including Bluetooth tethering, Market, Setup Assistant, ADAS ELKA and several MPU settings.

My main concern is how READ ALL / WRITE ALL works.

Unlike other ECUs where you can write a single changed parameter, the A-IVI HMI screen appears to require reading and writing all parameters together.

My questions:

1. If I use A-IVI 2.7 and press WRITE ALL, what happens to existing settings that aren't listed in 2.7? For example, will my existing TPMS configuration remain untouched, or could it be erased/overwritten?

2. Does WRITE ALL only write the parameters defined in that ECU version, or does it rewrite an entire configuration block?

3. If READ ALL successfully retrieves every parameter in 2.7 without showing NO DATA, does that mean it's safe to use, or could there still be compatibility issues?

4. Is there any way to get DDT4All to automatically detect and match my actual A-IVI ECU rather than manually selecting a version?

I'm particularly worried about losing existing working features like TPMS or potentially bricking the unit just to change one HMI setting.

Would really appreciate some clarification from anyone familiar with how DDT4All handles WRITE ALL when the selected ECU definition isn't an exact match.

Thanks!

[tvisura-a11y]

On the A-IVI HMI screen, the READ ALL button executes only ONE read command 222108 (reads many parameters).
Accordingly, WRITE ALL writes only to the HMI.
3. If READ ALL successfully reads all parameters in version 2.7 without displaying NO DATA, then it is safe to use WRITE ALL
4. It is not possible to configure DDT4All so that it automatically detects and connects your real A-IVI ECU. You can only change the database file for automatic detection.