100 ENGINE COMPONENT AND LOCATION Unit injectors are categorized and coded with regard to tolerances. Whenever a unit injector is replaced, the replacement injector MUST be programmed for the cylinder in which it is installed. This is done by programming EECU parameters using the VCADS pro or the Premium Tech Tool (PTT) to set Injector Trim parameters with the trim codes marked on the injectors. Note: The dimension by which the injector nozzle extends from the head is critical. This means that machining the head in any way that changes this nozzle extension is not permitted. W2033335 1. Serial No. 2. Unit Calibration No.