Originally Posted by RocketSled
Yes. The Tech-II scanner will see recorded codes even when the codes have been cleared from the DIC.
The only things I'm unsure of are whether or not all the codes are covered by this rule, for how many ignition cycles old codes are retained, and how much history is saved.
Generally, if the fault that triggered the code and light (some faults do not trigger the light but still leave a code because they do not directly have an impact on vehicle emissions or safety) does not occur for three (3) cold-hot-cold cycles, that nasty engine light will go out for the most part. The codes will stay for 40 of those cycles if I remember correctly (somebody PLEASE CORRECT ME IF I AM WRONG!!!!) assuming the code does not get set again and then will be cleared. Also, I can't remember the amount of faults needed per cycles to set a code, but if I do remember, I will post it-or someone else can post the number if they are not having a mental lapse like I am.
The scan tool will reset the majority of codes, if not all of them, and a Tech II will reset the codes for the specified system, but not all systems. The Tech II basically has this as a saftey so a tech can't accidentally reset all control modules and clear all codes in case the vehicle come in with multiple issues. I must add that the professional grade scan tools will only allow the user to reset one control unit at a time instead of resetting all, which is especially important with ABS and airbag systems as that would be a bad thing to erase those codes without diagnosing and/or repairing the problem.
I hope this helps,