Error P0133 – how to fix?

P0133 Error code definition

P0133 O2 Sensor Circuit Slow Response

What does the code 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 fuel-to-air ratio of the engine. The air-to-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 ECM’s air-fuel ratio by sending a voltage reading to the ECM.

Changing the amount of gas and air hitting the sensor should change the output voltage of the O2 sensor. The output voltage from the O2 sensor should change as fast as you can press the gas pedal because when you press the pedal, the air-fuel ratio changes instantly.

P0133 indicates the ECM detects that the O2 sensor is not changing its output voltage fast enough to change the air-fuel ratio. Hence, the definition of error code P0133 is the “slow response” of the O2 sensor circuit because the circuit is not responding fast enough.

What causes the code P0133?

• O2 sensor defective
• There is a leak in the exhaust manifold
• Vacuum leak in the engine
• O2 sensor harness shorted or open
• Soot or oil build-up on the O2 sensor (excessive build-up clogs the ports the sensor uses to measure air-to-fuel ratio)
• Dirty air mass flow meter
• Incorrect fuel pressure

What are the symptoms of the P0133 code?

• The engine stalls or fires improperly
• Low fuel economy
• Loss of engine power

How can a technician diagnose the P0133 code?

• Visually inspect the wires associated with the O2 sensor for fraying and saturation with contaminants such as oil.
• Measures the O2 sensor output voltage with a scan tool or multimeter.
• Visually inspect the sensor base for soot, thermal stress, or oil deposits
• Check the air inlet and vacuum hoses for leaks.

The most common errors when diagnosing the P0133 code

• Apart from the fact that a dirty air mass flow meter may cause the O2 sensor circuit to respond slowly.
• No cleaning of electric wires and O2 sensor terminals.
• Missing the fact that a leaking vacuum line or a leak in the intake manifold could 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 as the O2 sensor is used to keep the amount of harmful pollutants emitted by the engine to a minimum. The O2 sensor keeps contaminants to a minimum by adjusting the air-fuel ratio to a level that will not form too much contamination.

The environment is more sensitive to exhaust pollution than most people realize, so it’s best to replace a damaged O2 sensor.

What repairs can fix the code P0133?

1. Typically, replacing the oxygen sensor clears the P0133 code.
2. Sometimes the sensor itself is not the cause of the P0133 code, so the technician should check for other faults such as vacuum leaks, a dirty mass air flow sensor, or leaks in the exhaust system.

Additional comments regarding code P0133

When diagnosing the P0133 code, check for vacuum leaks, intake leaks, and check the mass air flow sensor for oil build-up or other debris to avoid any chance of misdiagnosis.