Suzuki Club UK

Rhinoman wrote:During normal running the ECU will drive the mixture alternately rich and lean and measure the time taken for the sensor to respond, from that it deduces if the mixture requires adjusting. If the first sensor isn't fitted and the ECU does not see the reading change with the mixture then it will set a fault code and revert to base settings - how much effect that has depends on the condition of the engine. The second sensor is used to test the effectiveness of the cat, no sensor will flag a fault but you can connect the sensor and leave it in free air, that's usually enough to cheat it.