Ecu 3.5.5.2 - Honda

“3.5.5.2 fixed the annoying cold start stumble on my 2019 Passport. Economy mode is actually usable now without feeling like the car is asleep.”
– @JseriesV6

“Tuners say avoid 3.5.5.2 if you plan on running E30 blend. The fuel pressure logic changed.”
– @BoostedK20C honda ecu 3.5.5.2

Version 3.5.5.2 is a firmware/driver update for Honda’s ECU communication interface (the HIM – Honda Interface Module). It’s used by dealerships and independent shops running i-HDS software to talk to engine, transmission, ABS, airbag, and other ECUs on most Hondas/Acuras from roughly 1996–2020. “Tuners say avoid 3

Unlike the crude OBD1 ECUs, the 3.5.5.2 firmware uses adaptive closed-loop fueling with a wideband-like narrowband O2 sensor strategy. The ECU learns long-term fuel trims (LTFT) and short-term fuel trims (STFT) more accurately. For a naturally aspirated build (I/H/E), this ECU actually runs smoother than a chipped P28. Version 3