How to Read and Write PSA SID807 ECU using Flex Tool

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.

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