We often get asked what B1 and B2 and S1 and S2 with scan tool error code readings on Automotive ECUs.
So I just thought to give some assistance on this.
B1 means the sensor is located on the same bank of the engine that has the #1 cylinder. B2 is located on the opposite bank.
S1 means the sensor is located BEFORE the catalytic converter
S2 means the sensor is located AFTER the catalytic converter
