MECH AI · Diagnose

All codes › P0430

P0430 — Catalyst Efficiency Below Threshold (Bank 2)

P0430 is the Bank 2 counterpart of P0420. It is set when the engine control module compares the upstream and downstream oxygen sensor signals on Bank 2 and determines that the catalytic converter for that bank is no longer storing and releasing oxygen efficiently. P0430 only applies to V-engines and inline engines with separate exhaust banks; four-cylinder engines do not set P0430.

P0430 means catalyst efficiency below threshold (bank 2). A vehicle usually stays drivable short-term with this code, but it should be diagnosed promptly. The most common cause is worn or contaminated catalytic converter on bank 2 (typically $600–$2,400). Causes and cost vary by make and model; confirm the root cause before replacing parts.

Severity: moderate powertrain Safe to drive (short term)

Reviewed by MECH AI Editorial · Last verified

What does P0430 mean?

P0430 is the Bank 2 counterpart of P0420. It is set when the engine control module compares the upstream and downstream oxygen sensor signals on Bank 2 and determines that the catalytic converter for that bank is no longer storing and releasing oxygen efficiently. P0430 only applies to V-engines and inline engines with separate exhaust banks; four-cylinder engines do not set P0430.

What are the symptoms of P0430?

What causes P0430?

Cause Likelihood Estimated repair (USD)
Worn or contaminated catalytic converter on Bank 2 Most common $600–$2,400
Failing downstream (post-catalyst) O2 sensor on Bank 2 Common $150–$450
Exhaust leak upstream of the Bank 2 downstream O2 sensor Common $100–$500
Untreated misfire or rich/lean condition on Bank 2 cooking the cat Occasional $200–$1,200
Oil or coolant contamination from internal engine wear poisoning the cat Rare $1,200–$3,500
Cheap aftermarket catalytic converter that does not meet OEM efficiency Occasional $600–$1,800

Repair costs are typical US ranges and vary by make, model, model year, and labor rate. A diagnostic trouble code is a symptom, not a guaranteed failed part — confirm the root cause before replacing anything.

Is it safe to drive with P0430?

In most cases a vehicle stays drivable for short trips with P0430 active, but you should diagnose and repair it promptly. This is a moderate-severity code — ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on your specific make and model.

How to diagnose P0430

  1. Identify Bank 2 on this engine

    Bank 2 is the cylinder bank that does not contain cylinder 1. On most transverse V6 engines (Honda, Toyota, Nissan) Bank 2 is the bank closer to the radiator. On longitudinal V8 engines like Ford modular, Bank 2 is the passenger side. Confirm in the service manual before replacing parts.

    Tools: Vehicle-specific service information

  2. Pull all stored and pending codes

    Address any misfire codes (P0300-series) or fuel trim codes (P0171, P0174) on Bank 2 first. They will continue to damage the catalyst until resolved.

    Tools: OBD-II scan tool

  3. Inspect the Bank 2 exhaust for leaks

    Cold-start the engine and listen along the Bank 2 manifold, header, flex pipe, and gasket seams. A leak upstream of the rear O2 sensor pulls in fresh air, mimics catalyst failure, and is far cheaper to repair than a converter.

    Tools: Mechanic's stethoscope, Flashlight

  4. Graph upstream vs downstream O2 sensors on Bank 2

    With the engine warmed up and held at 2000 RPM, graph the Bank 2 upstream O2 sensor (should switch rapidly between 0.1 V and 0.9 V) and the Bank 2 downstream O2 sensor (should stay relatively steady around 0.6–0.8 V). Downstream that mirrors upstream confirms catalyst loss.

    Tools: Scan tool with graphing PIDs

  5. Rap-test the Bank 2 catalytic converter

    Tap the converter body with a rubber mallet. A rattle confirms the ceramic substrate has broken apart. Visual inspection of the inlet and outlet through a flashlight beam can sometimes reveal melted cells.

    Tools: Rubber mallet, Flashlight

How do I fix P0430?

Pick your vehicle for a P0430 diagnosis

Select your exact year, make, and model below to get a diagnostic guide tuned to your vehicle's known failure patterns and TSBs.

2010-2014

2015-2019

2020-2024

Related diagnostic codes

P0430: frequently asked questions

What does diagnostic trouble code P0430 mean?

P0430 is the Bank 2 counterpart of P0420. It is set when the engine control module compares the upstream and downstream oxygen sensor signals on Bank 2 and determines that the catalytic converter for that bank is no longer storing and releasing oxygen efficiently. P0430 only applies to V-engines and inline engines with separate exhaust banks; four-cylinder engines do not set P0430.

What are the symptoms of P0430?

Check Engine Light is illuminated (steady). Slight loss of fuel economy. Faint sulfur or rotten-egg smell from the exhaust. Vehicle fails OBD-II emissions / smog testing. Rarely any drivability issue at idle or cruise

What causes P0430?

Worn or contaminated catalytic converter on Bank 2 (most-common). Failing downstream (post-catalyst) O2 sensor on Bank 2 (common). Exhaust leak upstream of the Bank 2 downstream O2 sensor (common). Untreated misfire or rich/lean condition on Bank 2 cooking the cat (occasional). Oil or coolant contamination from internal engine wear poisoning the cat (rare). Cheap aftermarket catalytic converter that does not meet OEM efficiency (occasional)

Is it safe to drive with P0430?

In most cases a vehicle stays drivable for short trips with P0430 active, but it should be diagnosed and repaired promptly — this is a moderate-severity code. Ignoring it can lead to further damage or a failed emissions test. Specific tolerance varies by make and model.