SERVICE · CAT OFF
Catalyst OFF software
Disable catalyst efficiency monitoring and mirror the post-cat lambda to the pre-cat sensor — required after fitting a decat downpipe.
Typical symptoms / why workshops apply CAT OFF
- P0420 / P0430 after exhaust upgrade
- Catalyst efficiency below threshold MIL
- Post-cat lambda signal mismatched after de-cat
- MIL refusing to clear after exhaust install
What Softechpro V5 actually patches when you select CAT OFF
- Mirrors the upstream O2 sensor signal as the downstream sensor.
- Suppresses the catalyst-efficiency comparison logic.
- Disables the P0420 / P0430 trigger.
- Auto-checksum.
ECU families supported for CAT OFF
Bosch MED17 (gasoline)Bosch ME7Bosch MEVD17Siemens / Continental gasoline variantsHitachi / Denso gasoline
DTC codes commonly cleared by CAT OFF
5-step workflow
- Read out your ECU bin file via OBD or bench (KESS3, AutoTuner, MPPS, Trasdata, Flex, FRF flasher).
- Open Softechpro V5 and drop the .bin / .ori / .hex / .s19 / .frf onto the workspace. Softechpro auto-identifies the ECU family from the header signature.
- Select CAT OFF from the service tab.
- Hit Save patched .bin. The ECU-specific checksum is recomputed automatically.
- Flash the patched file back via your existing flasher. Reset adaptations via the OEM scan tool if required.
Legal notice
De-cat installations are illegal on EU road-registered vehicles. Off-road and motorsport use only.
Frequently asked questions
Do I need a wideband O2 sensor?
No. CAT OFF mirrors the existing factory lambda sensor signal. The downstream sensor can remain physically installed (it just gets ignored) or be removed.