what if my car is already programmed?

[JROBINSON1016]

I was thinking about getting a programmer,probably hypertech.just for the ability to change axle ratios or fan temps.I had to change my rear end a few weeks ago,& found out that it had a different ratio than is on my rpo code list.so,I'm not sure if someone has already set up a program on my vehicle,the speedo was correct.I know that you cant program another vehicle with a programmer if it hasn't been restored,what if my computer hasn't been restored because of the ratio change,if I buy a programmer,will I be able to use it?or will it not,because it is currently running a set program from another tuner?how do i know if it has been set with another tuner?

[Sarge]

I would ask the manufacturer of the handheld you are considering.

[HotRodCarts]

I have a Diablo Predator and it says to be sure you have a stock tune before using it. I'm not sure about the others.

[mrr23]

sometimes, the handheld may not be able to unlock the PCM because the guy that did the tuning put a code in the handheld won't recognize. if it does unlock the PCM, it may not overwrite every file inside the PCM which can cause running issues.