P0421 VOLKSWAGEN - Warm Up Catalyst Efficiency Below Threshold Bank 1
P0421 VOLKSWAGEN Possible Causes
- Warm Up Three Way Catalytic converter deterioration or malfunction
- Exhaust system leaks
- Loose front or rear HO2Ss
- Faulty front heater O2 sensor
- O2 sensors harness is open or shorted
- O2 sensors poor electrical connection
First diagnose P0421 VOLKSWAGEN code
Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded terminals.
P0421 VOLKSWAGEN Tech NotesAs the code description implies the P0421 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0421 code is combined with other codes, try fixing the other codes first.
Cost of diagnosing the P0421 VOLKSWAGEN code
Labor: 1.0The cost of diagnosing the P0421 VOLKSWAGEN code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
When is the P0421 VOLKSWAGEN code detected?The P0421 code is set when the Engine Control Module (ECM) detects rear HO2S value difference becomes closer to value of front HO2S. The ECM monitors when vehicle speed is 25-60 MPH, load is 22-45 percent and engine speed is 1000-3000 RPM.
P0421 VOLKSWAGEN Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P0421 Volkswagen DescriptionThe 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.
P0421 VOLKSWAGEN More InformationNeed more information on how to fix the P0421 VOLKSWAGEN code?
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Need more help?Get the P0421 Volkswagen code diagnosed by a professional: Find a repair shop in your area
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