P0133 Error code definition
P0133 O2 sensor circuit – slow response
What does P0133 mean
Bank 1 Sensor 1 is a sensor that is used by the computer (ECM) to monitor the amount of oxygen leaving the engine. The ECM uses the signal from the O2 sensor to adjust the engine’s fuel/air ratio. The air/fuel ratio is adjusted by the ECM to regulate fuel consumption and reduce the amount of air pollutants leaving the engine. The O2 sensor indicates the air/fuel ratio to the ECM by sending a voltage reading to the ECM.
Changing the amount of gas and air going to the sensor should change the O2 sensor output voltage. The O2 sensor output voltage should change as quickly as possible, because when you press the pedal, the air/fuel ratio changes immediately.
P0133 indicates that the ECM detects that the O2 sensor is not changing its output voltage fast enough to change the air/fuel ratio. Thus, the definition of error code P0133 is “slow response” of the O2 sensor circuit because the circuit is not responding fast enough.
What causes code P0133?
- O2 sensor defective
- Exhaust manifold leak
- Engine vacuum leakage
- Short circuit or open in O2 sensor wiring
- Soot or oil buildup on the O2 sensor (excessive buildup will clog the ports that the sensor uses to measure the air/fuel ratio)
- Dirty air mass flow meter
- Incorrect fuel pressure
What are the symptoms of code P0133?
- Engine shuts down or misfires
- Low fuel economy
- Engine power loss
How can a technician diagnose a P0133 code?
- Visually inspect the wires associated with the O2 sensor for wear and saturation by contaminants such as oil.
- Measure the O2 sensor output voltage with a scan tool or a multimeter.
- Visually inspect the sensor base for soot saturation, thermal stress, or oil deposits
- Check the air inlet and vacuum hoses for leaks.
Most common errors when diagnosing the P0133 code
- Omitting the fact that a dirty air mass flow meter can cause a slow response of the O2 sensor circuit.
- Failure to clean the wires and electrical terminals of the O2 sensor.
- Ignoring the fact that a leaking vacuum line or intake manifold can cause erroneous O2 sensor voltage readings. Voltage readings that may set the P0133 code
How serious is the P0133 code?
This particular code can be harmful to the environment because the O2 sensor is used to keep the amount of harmful pollutants emitted by the engine to a minimum level. The O2 sensor keeps the amount of pollutants to a minimum by adjusting the air/fuel ratio to a level where not too many pollutants will be produced.
The environment is more sensitive to exhaust pollutants than most people realize, so it is best to replace a faulty O2 sensor.
What fixes can repair a P0133 code?
- Normally, replacing the oxygen sensor will clear the P0133 code.
- Sometimes the sensor itself is not the cause of the P0133 code, so the technician should check for other malfunctions such as vacuum leaks, a dirty mass airflow sensor, or leaks in the exhaust system.
Additional notes on the P0133 code
When diagnosing a P0133 code, check for vacuum leaks, inlet leaks, and check the airflow sensor for oil mass or other debris to avoid misdiagnosis assumptions.
