AI enthusiast Muhammad Zulali uses Claude and Codex to hack 1994 Jeep Cherokee engine control unit, passing US California smog tests
Muhammad Zulali leveraged AI to reverse-engineer a legacy vehicle's SCI bus and inject code, solving emission failures with $15 in hardware.
According to Tom's Hardware, car owner Muhammad Zulali used Anthropic's Claude and OpenAI's Codex to fix the emissions issues of a 1994 Jeep Cherokee, allowing it to pass California smog tests. The project utilized hardware worth no more than $15, including an Arduino Nano microcontroller.
Zulali faced the challenge of communicating between a modern laptop and the vehicle's primitive Engine Control Unit (ECU). Claude guided him to identify that the car used a Chrysler SCI bus at approximately 7,800 baud, with electrical signals inverted compared to a typical serial port. By using the Arduino Nano to handle signal inversion and connect to the Cherokee's 6-pin diagnostic plug, the system was able to read data such as coolant temperature and battery voltage.
After obtaining initial data, Claude assisted in collecting engine data and fault codes during test drives at 25 mph and 50 mph to diagnose the cause of excessive NOx emissions. Since the ECU firmware was not reflashable, Zulali instead used Codex to write code that injected custom logic into a nearby EEPROM, adjusting fuel pressure and other parameters to meet emission standards.
"Claude did most of the diagnostic work and Codex did pretty much all of the memory work," admitted Zulali. "I just did the wiring and the driving." The project has been open-sourced on GitHub as xj-scanner under the GPLv3 license. This case demonstrates the practical application capabilities of large language models in reverse-engineering legacy hardware protocols and guiding embedded system debugging.