P0430 — Catalyst System Efficiency Below Threshold (Bank 2)
P0430 is the Bank 2 version of P0420. The downstream O2 sensor on Bank 2 indicates the catalyst is no longer efficient. Bank-specific O2 graphing and leak inspection prevent unnecessary converter replacement — treat P0430 exactly like P0420 but focus on Bank 2 components.
Fault Overview
Failed Bank 2 catalytic converter, lazy Bank 2 upstream O2 sensor, exhaust leaks on Bank 2, and misfires or fueling issues that damaged the Bank 2 catalyst are the primary causes. On some engines the Bank 2 converter is harder to access — confirm diagnosis before removal.
Engine & Platform Coverage
Symptoms
- •P0430
- •catalyst efficiency bank 2
- •Bank 2 catalytic converter
- •P0430 V6
- •P0430 Ford
- •P0430 GM
Possible Causes
- 1.Failed Bank 2 catalytic converter
- 2.Lazy Bank 2 upstream O2 sensor
- 3.Exhaust leaks on Bank 2
- 4.Misfires or fueling issues that damaged Bank 2 catalyst
Wiring & Circuit Notes
Bank 2 upstream and downstream O2 sensor connectors and wiring. Check for exhaust heat damage.
DVOM Specs & Sensor Tests
Bank 2 upstream O2 switching frequency and amplitude. Downstream O2 activity. Exhaust backpressure. Temperature before and after the converter.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
4 steps locked behind Technician Mode- 1Step 1 — Graph Bank 2 Upstream and Downstream O2 Sensors: Graph Bank 2 upstream and downstream O2 sensors at 2000–2500 rpm. The downstream should be relatively flat if the catalyst is working.
- 2Step 2 — Verify Upstream O2 Sensor Switching: Verify the Bank 2 upstream O2 sensor is switching properly. A lazy sensor is a very common false P0430 trigger.
- 3Step 3 — Inspect Bank 2 Exhaust for Leaks: Inspect the Bank 2 exhaust system for leaks before and around the converter.
- 4Step 4 — Review Misfire and Fuel-Trim History for Bank 2: Review misfire and fuel-trim history for Bank 2 events that may have damaged the catalyst.
- 5Step 5 — Replace Converter Only After Proof: Replace the Bank 2 catalytic converter only after all other causes are eliminated.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Typical Repair Costs
Replace Bank 2 upstream O2 $100–350; repair exhaust leaks $100–400; replace Bank 2 catalytic converter $300–2,000+.
Related Codes & Pages
Start Diagnosing This Fault Now
AI Diesel Tech walks you through every evidence gate in the correct order. Choose the plan that fits your shop.
AI Diesel Tech — The Technician's Diagnostic Engine
AI Diesel Tech diagnostic logic is built by an ASE Certified Diesel Technician and engineered for professional shop use. Trusted by technicians nationwide — used in shops, fleets, and training programs.
Summary
Use the AI Diesel Tech diagnostic engine to run this code through a structured, evidence-gated sequence and get a confirmed root cause before any parts are replaced.