We’ll walk through the process of reading and writing the SID 807 ECU in a 2011 Citroen C4 1.6L Diesel (110 HP / 82 kW) using the FLEX programming tool. This demonstration covers OBD-based tuning, including how to disable Start-Stop functionality—a common request from vehicle owners.
Tools & Preparations
FLEX Programming Tool (OBD connection)
Battery Maintainer (recommended for stable voltage)
Citroen C4 SID 807 ECU (2011 model in this case)
Note:
- Always verify the ECU hardware number before proceeding.
- If unsure, the FLEX tool can auto-detect the correct ECU type.
Step-by-Step Procedure
1. Identify the ECU
- The FLEX tool allows you to manually input the vehicle details (Citroen C4, 1.6 Diesel, SID 807) or automatically detect the ECU.
- If the wrong ECU is selected, the tool won’t establish a connection, preventing accidental errors.
2. Read the ECU via OBD
- Connect the FLEX tool to the OBD port (which, in French cars, can be tricky to locate—check under dash panels!).
- Select “Read Virtual Map” – the tool downloads the current ECU data from its server.
- Save a backup before making any modifications.
3. Modify & Write the Tuning File
- In this case, the goal was to disable Start-Stop.
- The modified file is uploaded back to the ECU via OBD (no bench mode or boot mode required).
- The FLEX tool performs checks and corrections automatically before writing.
4. Complete the Process
- After writing, the tool runs a coding procedure.
- Disconnect the FLEX tool, start the car, and verify that the Start-Stop function is now deactivated.
Key Observations
Faster than OBD-only tools – The FLEX tool streamlines the process with server-based virtual maps.
No need for boot mode – Avoids the complexity of direct ECU reading in many cases.
Stable & Reliable – No reported issues with SID 807 ECU writing.