Is the MD1CS003 Really Locked? Does my tuner just have the wrong tools?
Should I keep calling every tuning company until someone tells me that they will do it?

We hear these questions almost every day — so we’ve put together this guide to clear up the confusion and save you time.

“A company told me they’ve done this ECU before — they say they do them all the time. Can they really do it?”

Let’s break it down.

Which MD1CS003 ECUs Are Fully Locked?

For vehicles produced from 2020 onward, MD1CS003 ECUs with Bosch part numbers 0281037198 and higher are currently impossible to read or write with any tuning tools on the market. This includes:

• 0281037200

• 0281039490

• 0281039556

It doesn’t matter how many tuners you contact—none of them can program these ECUs, regardless of what they claim. Sending your ECU or visiting in person will just be a wasted trip. Yes they may have done other MD1CS003 ECUs, but the locked ECUs are locked at the processor level, it’s just not possible (yet).

Note: Locked Bosch numbers differ between brands. This article specifically refers to PSA Toyota Opel vehicles with MD1CS003.

Which MD1CS003 ECUs Can Be Programmed and Remapped?

As of the time of writing this article June 2025, no tools support programming the MD1CS003 over OBD. However, programming using bench service mode is works well on ECUs which are accessible.

Bench programming this ECU is somewhat straightforward—no need to open the unit. Communication is done over CAN High, CAN Low, Power, and Ground cables direct to the ECU connector.

All MD1CS003 ECUs with Bosch numbers lower than 0281037198 can be bench programmed. For example:

• 0281034708

• 0281035332

• 0281035365

• 0281037101

Why Are Some newer ECUs Locked?

The MD1CS003 ECU uses the Infineon Aurix TC298 processor, which includes several One Time Programmable (OTP) Zones. If the lock bit is set in this area, it can never be undone—not even by the manufacturer.

The only theoretical workaround is to remove and replace the processor for a brand new and never before programmed unit, which is complex and costly. While this may be cracked in the future, for now, these ECUs are permanently locked.

It’s actually likely these will be cracked at some point, likely with a write only option, we know this because PSA does offer updates using dealer level diagnostic equipment, so of course the ECU isn’t fully write protected otherwise software updates would be locked out. Even if tuning tool suppliers had the seed keys for these ECUs, they are now unwilling to release this as a useable program, mainly because they don’t want Bosch to patch it like they already did on the post 2020 ECUs. There’s also a great business model that these tool companies can make a lot more money if they lock out every smaller tuning company in the world, and thus every tuner needs to then send the ECU to the tool providers for processor unlocking with a big fee.

Does HDI Tuning Offer a Solution?

Yes—we have developed a (partial) workaround using a replacement ECU. However, it’s complex, time-consuming, and expensive. We even had to create our own software because there isn’t a direct match available and most cars have different software so custom work is required for each new job. As it stands, we’re already fairly busy and we are not advertising or offering this service on our website just yet until we can find more time and a way to streamline the process.

Until we find a more cost-effective method, this solution will likely remain unavailable/unaffordable to most customers.

If you have a faulty ECU and you’re really stuck then we might help you out depending on how busy we are and the specifics of the job.

Please note: We will not disclose details of our method or offer support to other tuning companies. Please don’t ask.

Can I fit an unlocked ECU from an older model and then tune this ECU?

In an ideal world this would be the best/easiest solution and it’s the one we thought would be the most straight forward when we first approached this project.

Unfortunately this isn’t a feasible way to do this, there are several reasons why this doesn’t work, but mainly it’s because of software incompatibilities and different options fitted to the vehicles. There’s a lot more to it but of course that’s proprietary information.

Please do not order an unlocked ECU from our ECU store with the intentions of retro fitting it to a newer model, we will ask for a photo of your ECU so we can match the correct part, you cannot simply order a different one and fit it, there will be lots of faults and problems.

Does HDI Tuning offer an unlocked plug and play remapped ECU for MD1CS003 before 2020?

Yes, we can unlock all variants which can be accessed using our programming equipment, everything before 37198. In time these will be added to our webshop.

Currently we already have a lot to do, and every ECU must be configured to match the vehicle so it’s a time consuming process.

If you specifically need an unlocked ECU because of a fault, then get in touch. If you just want a remap then it’s easier to send us your existing ECU for tuning.