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The lambda sensor measures the oxygen in the exhaust gases and lets the ECU meter the fuel: as it ages it becomes “lazy” and the mixture stays rich. The result is high consumption, emissions out of limits and a catalytic converter under stress.

Front and rear sensor

• Upstream (before the catalytic converter): controls injection. If faulty, consumption and emissions worsen immediately
• Downstream (after the catalytic converter): monitors the converter’s efficiency. If faulty, the typical fault is P0420 with no real driving problems

Typical symptoms

• Increased consumption with no apparent reason
• Rough idle, hesitation under acceleration
• Strong smell from the exhaust
• Fault codes P0130-P0141, P0171, P0172
• Car failing the emissions test at the MOT

What to do

• Have the sensor’s live signal read: a lazy sensor is recognised by its slow oscillation
• Rule out intake and exhaust leaks before replacing
• Use quality parts: cheap universal sensors often give signal problems

How MasterTuning helps

We check the component with real measurements, not by elimination: flow rates, pressures, corrections and signals read directly from the ECU. We repair, replace and recalibrate the software when needed. Centres throughout Italy.

Read more: vehicle database · what is ECU remapping · original files archive

Want an accurate diagnosis? Contact MasterTuning and book at your nearest centre.

Frequently asked questions

How long does a lambda sensor last?

Roughly 100,000-150,000 km, but oil consumption and poor-quality fuel degrade it sooner.

Does the lambda sensor affect fuel consumption?

Yes, a lot: it is the sensor that regulates the amount of fuel injected in normal driving conditions.

Can you drive with a faulty lambda sensor?

Yes for short distances, but with high consumption and emissions, and a risk of damaging the catalytic converter.