1994 Jeep Cherokee owner hacks 32-year-old car with Claude AI to pass California smog tests

An AI enthusiast managed to get his old 1994 Jeep Cherokee to pass the California smog tests, all thanks to the help of AI and a little electronics wiring skill. This 32-year-old car had only a primitive engine computer, but after connecting it to a laptop via an Arduino Nano board, many settings could be read and eventually controlled.

The above video documents Muhammad Zulali’s journey from the Jeep failing consecutive smog tests, to managing to hook it up and get readings from the ECU, to tuning and fixing the engine emission issues. All the while, Claude provided guidance, and Codex wrote any required code.

This rather old Jeep was failing the California smog tests due to producing too much NOx at certain test speeds. It initially failed at 25mph. Then, after Zulali made some adjustments to the oxygen mix, it failed at both 25mph and 50mph. Yes, it got worse.

Zulali admits he was effectively making adjustments blind, and subsequent regulatory pollution tests cost nearly $100 each time. That’s clearly a big problem, but we have AI to help us in 2026. Actually, it was AI and a $3 microcontroller, contributing to a total bill of materials of no more than $15.

The first hurdle facing the possible AI solution was the question of how to interface an old car and a new laptop. Claude told the Jeep owner that the engine communicated on a Chrysler SCI bus at ~7,800 baud, which was electrically inverted compared to a typical serial port. An Arduino Nano can handle the required inversion and hook up the data to a modern computer. The Nano was breadboarded, with a few necessary wires, three of which connected to the 6-pin diagnostic plug in the Cherokee.

The first connection attempt was a success, but only coolant temperature and battery voltage were charted by the system to begin with. Zulali wanted more data points plus some controls to fix the smog test problem. After a couple of red herrings regarding the engine “running rich” with 22% extra fuel, based on other car model data, the Jeep owner got Claude to collect data from test drives. The AI logged engine data and fault codes during a drive at 25 mph and at 50 mph to see what was happening. It was also let loose to control things like fuel pressure.

With what looked like a credible diagnosis and solution in hand, Zulali wanted to reflash the car’s main ECU with AI-tweaked code that would mean it could pass all the California smog tests. Unfortunately, this car’s computer was just a few months too old to feature reflashable firmware. Instead, the Jeep owner got Codex to inject and run custom code inside a nearby EEPROM.

“Claude did most of the diagnostic work and Codex did pretty much all of the memory work,” admits Zulali. “I just did the wiring and the driving.” He added that he didn’t need the services of a mechanic or a Chrysler dealer tool for this feat.

In addition to the video, the Cherokee emissions fixer has created a GitHub repository for this project, dubbed xj-scanner. It is free software distributed under the GPLv3 license.

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