Fault processing

Emission increase (CARB B1 and CARB B4) 

During the first 1000 engine revolutions, the sum of all detected misfires is calculated. If the sum of all the misfire detected at the end of the first 1000 engine revolutions is above a threshold, then a CARB B1 fault is detected.

After the first 1000 engine revolutions, the same process is used during the complete drive cycle. If at least 4 periods of misfires above threshold are recorded, then a CARB B4 fault is detected.

Catalyst damage (CARB A) 

For each individual misfire detected, a weighting factor is applied depending on the running conditions (engine load and engine speed). The sum of the weighting factor adjusted misfires is computed during 200 engine revolutions. At the end of this period, a FTP cycle recognition is performed. If the sum of the weighting factor adjusted misfires is above a threshold and a FTP cycle not recognized, then a CARB A fault is detected. If a FTP cycle is recognized and if 3 periods of sum of weighting factor adjusted misfires above the threshold are recorded, then a CARB A fault is detected.