Fault code P0133 – a step-by-step guide to diagnosing and fixing it

Error code P0133 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected that the lambda sensor upstream of the catalytic converter (bank 1, sensor 1) is responding too slowly to changes in the fuel/air mixture. This DTC P0133 indicates a delayed response time of the oxygen sensor, which can affect the engine control. The designation may vary slightly for different manufacturers, but the basic problem remains the same.

What causes can this error code have?

• Defective lambda sensor (O2 sensor)
• Contaminated or aged oxygen sensor
• Damaged wiring to the lambda sensor
• Corroded or loose plug connections
• Defective engine control unit
• Leaks in the intake system
• Clogged air filter
• Fuel system problems (injectors, fuel pump)
• Exhaust gas leaks upstream of the lambda sensor

What symptoms occur in parallel with fault code P0133?

• Increased fuel consumption: The vehicle requires more fuel than usual
• Uneven idling: The engine runs unevenly when stationary
• Loss of power: Reduced engine power during acceleration
• Exhaust odor: Increased or unusual odor from the exhaust
• Engine misfires: Jerking or stuttering while driving
• Poor exhaust values: Increased emissions during the emissions test

How can the problem with error code P0133 be rectified?

• Repairing trouble code P0133 requires a systematic approach to identifying and eliminating the cause.
• Replace the lambda sensor completely, as a sluggishly reacting sensor cannot usually be repaired and must be replaced with a new original or high-quality replica sensor
• Check, clean or repair the wiring and plug connections to the oxygen sensor, including checking for corrosion, breakages or loose contacts
• Replace the air filter and check the intake system for leaks, as dirty filters or incorrect air supply can affect the sensor values
• Have the fuel system cleaned, check the injection nozzles and, if necessary, replace the fuel filter to ensure optimum mixture formation
• Check the exhaust system for leaks upstream of the lambda sensor and seal it, as extraneous air can falsify the measured values
• Read out the engine control unit, reset it and have it professionally checked or replaced if the error code occurs repeatedly