[mobythevan]

It would not be unusual at all for a car with a wideband O2 sensor to enter closed loop mode quickly. With the wideband the closed loop can control warmup at a richer AFR and then transition to a leaner AFR when warmed up. With a wideband there is almost no reason to stay open loop except start up and maybe after start enrichment because AFR can be controlled across a wide range. With a narrowband O2 sensor it wouldn't make a lot of sense for the car to enter closed loop until the engine is warm because you will only be correcting to 14.7 AFR. My 2 cents