I have a strange issue. Six months ago I changed out an old battery and of course it reset the I/M readiness codes. I drove the car during this time, but two of the sensors never set - evap and catalyst. So I drove the car at highway speed and 'attempted' to complete a drive cycle to set the sensors. The Evap became set, but the catalyst still shows not ready. So I let it sit overnight and then drove this morning and now the EVAP sensor shows not ready along with catalyst. How can that be? I thought once set, it stays set unless the battery is disconnected. The battery is new and never disconnected since installed six months prior. Any ideas? I am using a Creader 6001 scan tool. This tool also causes the ABS / trac off light to blink. I wonder if that may be corrupting the setting.