I just got access to use a Mac Scanner for my car. I was playing around with it last night and It reads all kind of data including LT Fuel Trim and 02 mv readings. I am throwing a Cat efficency P0420 and EVAP No Purge Code P0441. I was also throwing Bank 1 & 2 Rich codes but they must have gone away when I changed plugs and wires. Can someone tell me what my mv at idle should be at RPM for my 02's? Or does it just depend? Also What should my BLM's be for my LT Fuel Trim? Also when I activate the EVAP purge solienoid with the scanner, it says it starts to Purge 100%? When I turn the test off, it's at 0% purge? When is it supposed to purge??

 

In closed loop, at idle or part load/part throttle, the O2 mV's should be cycling back and forth almost 10 times per second between 100-900mV's.... or even wider range. That is the nature of closed loop A/F ratio control.

BLM's are "long term fuel trim" and should be at or close to (+/-5%) 128. Anything higher, and the PCM is seeing lean O2 sensor readings and adding fuel to correct. Anything lower and the PCM is seeing rich O2 sensor readings and cutting fuel.

Have you read this? It's all explained there.

 

Nice!
Thanks Fred!