Cat drive cycle

[paddlenbike]

The year difference is weird, I will have to double check, I can't remember it it was 99 or 00 where the front o2 sensor changed to an A/f sensor and the tolerances for emissions tightened up a little bit.

It depends on whether its a CA or federal emissions truck. The 99 and 00 CA models use a wideband AFR sensor, however a 00 federal emissions model (like mine) still uses the older style narrowband O2. By 2001, essentially all models were like CA models.