Catalyst Efficiency Low (Bank 2)
P0430 means the catalytic converter on Bank 2 is no longer cleaning the exhaust efficiently enough to satisfy the ECM. The most common root cause is a worn-out converter that can no longer store oxygen, though a slow downstream oxygen sensor can mimic the same fault. Severity is moderate: the car still runs, but it will fail an emissions test and the problem worsens over time.
01. Most Common Causes
- The ceramic substrate inside the converter has broken down or been poisoned by oil, coolant, or excess fuel, so it can no longer store oxygen or reduce pollutants; the ECM sees the rear sensor signal start to copy the front sensor.
- The downstream oxygen sensor (Bank 2, Sensor 2) has aged or become contaminated and now switches too slowly, so its trace resembles the upstream sensor and the ECM reports low catalyst efficiency even when the converter is healthy.
- An exhaust leak ahead of or near the converter is drawing in false air; that extra oxygen skews the rear sensor reading and makes the ECM calculate an incorrect conversion efficiency.
- Misfires or a chronically rich mixture have overheated and partially melted the substrate; unburned fuel ignites inside the converter and destroys the precious-metal coating.
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Possible decrease in fuel economy
- Rotten egg smell from exhaust (if converter is severely clogged)
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect exhaust system for leaks or damage near Bank 2 converter.
Step 3: Monitor oxygen sensor readings with a scan tool; compare pre-cat and post-cat sensor voltages.
Step 4: Perform a catalytic converter efficiency test (e.g., using a propane torch or manufacturer-specific procedure).
Step 5: If converter is confirmed bad, replace it; if sensor is faulty, replace the sensor.
04. Tools You Will Need
- OBD2 scan tool with live data to compare the upstream and downstream oxygen sensor signals across the catalyst
- Infrared temperature gun to measure the temperature delta between the converter inlet and outlet
- Digital multimeter to check the oxygen sensor heater circuits and signal voltage
1. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but you may fail an emissions test and fuel economy may suffer. If the converter is clogged, it can cause overheating and damage other components.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Replacing a catalytic converter can range from $500 to $2,500 or more, depending on the vehicle and parts.