Start this post with one question: Can the Alientech Kess3 read and write a 2021 Citroën Berlingo with a Bosch MD1CS003 ECU?
Yes! You can safely read it in bench mode—this ECU is not locked.

So, back to the topic: how do you know if a PSA MD1CS003 ECU is locked or not?
Most MD1 ECUs produced from mid-2020 onward come with protection (Tprot), meaning they are locked. From experience, several 2021 PSA vehicles had locked ECUs.
To check whether a PSA MD1CS003 ECU is locked, look at the part number:
Locked: Series 4xx
Not Locked: Series 3xx

For example, here’s a locked ECU from a 2022 DS3:
BOSCH: 0 281 037 200 (MD1CS003)
PEUGEOT: 98 457 808 80
Manufacture Date: 14 March 2022
On the other hand, 3xx series ECUs can be read and written without issue.

A customer’s ECU with part number 98 337 was successfully programmed without any problems.

If the ECU is not locked, many ECU tools can read and write MD1CS003 ECUs. ECUHELP KT200 II is a great option for the job!