Run the car up to temperature and With VAG COM clear the fault codes, even if none appear. Look at block 99, box 4. This tells you if closed loop lambda control is active or not. When it becomes active, then look at box 3 of block 99, this is live lambda trim. Take a note of these values. Put the standard chip back into the ECU and let it idle up to temperature With VAG COM clear the fault codes, even if none appear. Again Look at block 99, box 4. This tells you if closed loop lambda control is active or not. When it becomes active, then look at box 3 of block 99, this is live lambda trim. T