Why does lambda coefficient outside the default limits… fail an MOT?

Lambda coefficient outside the default limits or the range specified by the manufacturer. Most commonly flagged on the Peugeot 106. The DVSA's MOT standards require this item to meet minimum safety thresholds — when it falls short, the tester logs it as a Major or Dangerous defect and the car fails outright.

How much does it cost to fix lambda coefficient outside the default limits…?

Costs vary depending on the vehicle, region, and severity. Use our MOT cost estimator for typical UK garage rates across the most common failure items.

Lambda coefficient outside the default limits… — MOT failure (42,069 cars, 2023)

Models most at risk.

Ranked by rate, not raw volume. A Fiesta shows every failure a lot because there are a lot of Fiestas. Rate = share of that model's own MOTs.

Top 30 by rate. 165 more models also logged this defect.

Cost orientation

Hard to predict in isolation — depends what's actually worn.

This defect doesn't map to a clean retail-part swap; ranges vary too widely without seeing the car. Use the estimator to bracket the all-in cost across the items most likely to surface alongside it.

Open estimator

Frequently asked.

Why does lambda coefficient outside the default limits… fail an MOT?: Lambda coefficient outside the default limits or the range specified by the manufacturer. Most commonly flagged on the Peugeot 106. The DVSA's MOT standards require this item to meet minimum safety thresholds — when it falls short, the tester logs it as a Major or Dangerous defect and the car fails outright.
How much does it cost to fix lambda coefficient outside the default limits…?: Costs vary depending on the vehicle, region, and severity. Use our MOT cost estimator for typical UK garage rates across the most common failure items.