P0420WarningO2 Sensor & Silencer • Car, Bike, Auto
Catalytic Converter System Efficiency Below Threshold (Bank 1)
कैटेलिटिक कन्वर्टर क्षमता कम (साइलेंसर कैटालिस्ट खराबी) — common code demo from the VahanScan app’s full offline DTC library.
Multimeter Testing Specifications & Pinouts
- Power Pin (VCC)
- 12V Heater voltage on Rear O2 Sensor
- Signal Pin
- Sensor 2 Signal: Steady 0.45V – 0.65V when catalyst is good
- Ground Pin Continuity
- Chassis ground (< 0.5 Ω)
- Coil / Heater Resistance
- Downstream sensor heater: 9.0 Ω – 16.0 Ω
💡 If Sensor 2 fluctuates between 0.1V - 0.9V like Sensor 1, catalyst has failed.
Fault Symptoms
- •Check Engine MIL light on dashboard
- •Rotten egg / sulfur smell from exhaust
- •Exhaust pipe getting extremely hot (glowing red under load)
- •Mild loss of top-end power
लक्षण
- •मीटर में चेक इंजन लाइट लगातार जलना
- •साइलेंसर से सड़े अंडे या गंधक जैसी बदबू आना
- •साइलेंसर का बहुत ज्यादा गर्म होना या लाल पड़ना
- •हाई स्पीड में गाड़ी की रफ्तार दबना
Probable Causes
- •Catalytic converter honeycomb melted or degraded
- •Downstream (Sensor 2) O2 sensor lazy or failing
- •Unburnt fuel burning inside catalytic converter due to previous misfire
- •Exhaust leak between manifold and converter
संभावित कारण
- •कैटेलिटिक कन्वर्टर की जाली का पिघलना या ब्लॉक होना
- •कैटालिस्ट के पीछे लगा दूसरा O2 सेंसर खराब होना
- •इंजन मिसफायर की वजह से कच्चा पेट्रोल कैटालिस्ट में जलना
- •साइलेंसर जोड़ से गैस लीक होना
Step-by-Step Repair Guide
- 1.1. Check live O2 Sensor 1 vs Sensor 2 graph in VahanScan: Sensor 1 must oscillate 0.1-0.9V, Sensor 2 must stay steady around 0.45V - 0.6V.
- 2.2. If Sensor 2 mirrors Sensor 1 oscillation, catalytic converter is degraded or hollowed out.
- 3.3. Inspect cat converter inlet with borescope for melted substrate.
- 4.4. Fix any upstream misfires (P0300) before replacing catalyst.
- 5.5. Clear DTC Mode 04 after replacing converter or downstream sensor.
Physical Sensor Location: Downstream O2 sensor is installed right after the catalytic converter chamber under the car floor.
Diagnose this code in your garage
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