Code B0133 indicates a fault in the control circuit for the washer fluid level sensor (sometimes labeled 'Av Sensor' for ambient visibility or automatic wiper systems). The monitoring module has detected an open, short, or out-of-range signal in the sensor's supply, ground, or signal wire.
The sensor float or internal reed switch can stick, corrode, or fracture, sending an erratic or fixed resistance value to the control module.
Chafed insulation, corroded terminals, or a disconnected plug at the reservoir or along the harness can create an open or short to ground/power.
Fluid with additives, oil contamination, or very low conductivity can prevent the sensor float from moving freely or alter the electrical signal.
Cracked reservoir, broken float arm, or debris blocking float travel will produce a false reading even if the sensor electronics are functional.
Internal driver or pull-up resistor failure in the BCM can mimic a sensor circuit fault; this is uncommon and should be confirmed only after sensor and wiring are verified.
Rarely. The BCM is the least likely cause; the sensor, its wiring, or the reservoir assembly are responsible in the vast majority of cases. Replace the module only after circuit and component testing confirm an internal driver fault.
Yes, the code does not affect engine or safety systems. You will lose low-washer-fluid warnings and possibly automatic wiper/headlight features until repaired.
The sensor float may be stuck, the sensor itself may have failed, or there is a wiring fault preventing the module from seeing the correct level signal.
No. B0133 is specific to the windshield washer fluid level sensor circuit; coolant level sensors use different codes and circuits.