It’s no real secret that modern-day cars are basically a collection of computers on wheels, which also means that we get all the joys of debugging complex computer systems and software with cars these days. Rather than a quick poke under the hood to rebuild a carburetor and adjust the engine timing by hand, you’ll be pulling out a scan tool to gain access to the computer and figure out why the darn thing won’t start after someone else used a scan tool on it, as happened to [DiagnoseDan].
The question was whether the third-party scan tool that was used by the owner had done something to the software settings that would prevent the engine of this 2012 Renault Megane RS from starting, such as erasing keys, or if it was something more subtle. With no stored fault codes and the engine having healthy fuel, spark, and cam sensor readings, the conclusion was that the ECU was not doing its fuel injector things for some reason.
Ultimately, the root cause was that the ECU had been modded, with a re-mapping performed in 2020, meaning that the scan tool that [Dan] was using couldn’t properly interact with the ECU. Reflashing the ECU with the original manufacturer’s firmware was thus the next step, which is pretty involved in itself.
Reinstalling the OS on the car proved to be the solution. Likely, the modded firmware had stored some fault codes, as the ECU normally doesn’t start the engine if there are active codes stored. The third-party scan tool was thus likely blameless, but the inability to just clear fault codes was the real issue.
