It`s late, and I`m at home-no books or data-, but an O2 sensor cannot cause a cold hesitation, as it is not turned on by the CTS until the engine is warmed up to a specific temperature. Heated O2 sensors turn on earlier, but not early enough to be part of a "cold hesitation."There`s something else wrong, maybe a bad connection, a leaking CTS, a basic setting wrong, whatever. John.