For OBD II vehicles, long term and short term fuel trim values will be shown in percentages. Freeze frame will also show fuel trim values as percentages. Fuel trim represents how much compensation the powertrain control module (PCM) must make from ideal conditions. A higher positive value for fuel trim indicates the PCM is commanding more fuel into the engine, this can be caused by vacuum leaks, restricted fuel injectors, and others. A highly negative value indicates a lean engine command, possibly caused by leaky injectors, and others.