Having read a few articles like "
New Exemption to Digital Millennium Copyright Act Broadens Protection for Vehicle Data Access", I got to thinking, what if we could reverse engineer the HHT tools..? Obviously a big job... But then I thought, what would ChatGPT have to say about it, so I uploaded HHT-Win to ChatGPT.. Here is a sample of just one question i asked: (I dont think this example used the uploaded data, but for other questions, it actually started to tell me how the program is architected)
What controllers can HHT-Win read?
HHT-WIN (Hand-Held Tester for Windows) can communicate with many
legacy Mercedes-Benz control modules, primarily from vehicles manufactured in the
1980s through early 2000s, including your
2002 SL500 (R129). Its coverage focuses on
K-line (ISO 9141) and
Mercedes proprietary protocol modules, not CAN-based systems.
Typical Controllers HHT-WIN Can Read
Engine & Transmission:
| Module | Name | Function |
|---|
| ME | Motor Electronics (ME-SFI) | Engine control (fuel, air, ignition) |
| LH | LH-Jetronic | Early engine management |
| EZL | Ignition control | Timing and knock detection |
| EGS | Electronic Gear Selector | Automatic transmission |
Chassis & Brakes:
| Module | Name | Function |
|---|
| ABS/ASR/BAS | Brake systems | Anti-lock, traction, stability |
| EA/ISC | Electronic Accelerator | Throttle-by-wire / idle speed |
| ESP | Electronic Stability | Stability control module |
Body & Interior:
| Module | Name | Function |
|---|
| IC | Instrument Cluster | Gauges, warning lights |
| EZL | Central Locking/Immobilizer | Security and access |
| AAC | Automatic Air Conditioning | HVAC control |
| SAM | Signal Acquisition Module | Light and switch control |
| ZGW | Central Gateway (rare) | Bus communication |
Safety Systems:
| Module | Name | Function |
|---|
| SRS | Supplemental Restraint | Airbags, seatbelt pretensioners |
| IR/CL | Infrared Remote / Central Locking | Key fob & locking control |
How It Works in Practice
- When you enter DAS and select a module in an older Mercedes (e.g., R129), if that module is not CAN-based, DAS launches HHT-WIN in a separate window.
- You’ll then see:
- Job options (e.g., read DTCs, erase DTCs, actuator tests)
- Short test (scan all available modules)
- Live data / analog values
Limitations of HHT-WIN
| Limitation | Detail |
|---|
| No CAN Bus support | Won’t talk to modern modules (e.g., post-2003) |
| No flash programming | Cannot update ECU firmware |
| Text-based UI | Functional, but very old-school |
| Not standalone | Must be launched from DAS/Xentry |
Confirmed R129 HHT-WIN Modules (2002 SL500)
You can expect support for:
- ME 2.0 / ME 2.1 (engine ECU)
- EGS51 (transmission)
- EA/ASR (throttle)
- SRS (airbags)
- AAC (HVAC)
- IC (cluster)
- ABS/ASR/BAS
Let me know if you want a list of
exact PRG files present in your installation — these determine which modules can be accessed.
