The power‑train control module has detected that the catalytic converter on bank 1 is not reducing exhaust emissions as expected. This can happen when the converter is worn, damaged, or when exhaust gases bypass it before reaching the sensor.
The converter’s internal substrate may be cracked, melted, or coated, reducing its ability to store oxygen and convert pollutants.
A leak before the catalyst allows unburned oxygen to reach the downstream sensor, falsely indicating low efficiency.
A malfunctioning sensor can cause incorrect fuel trim, leading to conditions that overwhelm the catalyst.
If the sensor reports erratic voltage, the PCM may incorrectly judge catalyst performance.
A rare software issue or sensor wiring fault can cause the module to misinterpret catalyst data.
No. The PCM itself rarely fails; the issue is usually a worn catalyst, exhaust leak, or faulty oxygen sensor.
Yes. Even a minor leak before the catalyst can introduce extra oxygen, making the PCM think the converter is inefficient.
It is the most common cause, but not the only one; exhaust leaks, bad O2 sensors, or sensor wiring problems must be ruled out first.
It should, but only if the underlying condition that triggered the code is fully resolved; otherwise the light may return.