Like others said; it depends on the car maker and the car type.

I just got from a Renault Megane which had a TPMS broken off so the message was constantly on display that the sensor was not right. Coded it out of the ECU really easily. Also BMW, Benz, VAG (VW/SEAT/SKODA) and some others are know to work great for the most part. Can't be sure of all since I did not do all of them yet however.

Which brands are you working on mostly?

I was playing around with maxisys and pressed the code all button for bmw e46. Now
she swings but do not want to start. It is now showing an anti tampering code on ews
3.3. The machine seems to be unable to erase the code

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 Did you try to do a ews key realignment? Not sure of your codes but it may have just got lost. Pretty easy to do a realign.you do it in either ecm or ews clear codes when done and your good to go.