Decat and 2nd lambda off explained

How the catalyst is monitored

A lambda sensor before the catalyst measures the mixture going in. A second sensor after the catalyst checks what comes out.

The ECU compares the two. A catalyst that is no longer storing oxygen shows a similar signal on both sensors, which triggers a catalyst efficiency fault.

What a decat or 2nd lambda off file changes

The file changes how the ECU judges the post-catalyst sensor and the efficiency monitor. The catalyst itself is not removed or modified by us.

BRV Tuning supplies the binary only. Any removal of the catalyst or pipework is outside our service.

Emissions-related files are supplied for off-road, competition, agricultural and export use only, and must not be used on public roads.

Decat / 2nd lambda off

Pricing: Master file price €45 ex VAT · slave (Tier E) €27.

Standalone calibration for supported ECUs. Send the original read, the ECU part number and the exhaust specification.

Common codes

• P0420Catalyst efficiency below threshold (Bank 1). The catalytic converter is not converting exhaust gases as well as the ECU expects.

Why the catalyst code appears

P0420 is the most common result of a worn or failed catalyst, or of a sensor fault. Check the sensors before assuming the catalyst is at fault.

Common fault codes

Codes vary by make, model and ECU. Read the stored codes on your own car before and after flashing.

• P0420Catalyst efficiency below threshold (Bank 1). The catalytic converter is not converting exhaust gases as well as the ECU expects.