Q: p1120 out of service code

Hi. The code P1120 is a problem with the throttle position sensor. The input from the throttle position was not what the computer expected and would cause the computer to go into a failure limp mode. When the computer is in this mode, you will have low power and transmission shifting will be harsh and erratic. This is normal for the computer, as it limits some operations during a major throttle position failure. You will have to replace the throttle sensor with a new one to ensure this problem is resolved. Used parts cannot be guaranteed to work, but if the part is no longer available through the dealer or aftermarket, then a used one is the only way to go. It is hit or miss on used parts. If you need further assistance, I recommend you have a certified technician, like one from YourMechanic, replace the throttle position sensor and inspect for other possible failing components on your vehicle.