P0425 - Catalyst Temperature Sensor Circuit Bank 1 Sensor 1
- Catalyst Temperature Sensor harness is open or shorted
- Catalyst Temperature Sensor circuit poor electrical connection
The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2 sensor).
A three way catalyst converter (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.
When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst malfunction is diagnosed.
P0425 VOLKSWAGEN Catalyst Temperature Sensor Circuit Bank 1 Sensor 1