EN

Severity: Low Code type: Generic (all makes)

P0430 Code: Catalyst System Efficiency Below Threshold (Bank 2)

The bank 2 converter on a V6, V8 or split-exhaust engine isn't cleaning the exhaust well enough.

At a glance

Severity: 2/5 – Low2/5

Severity: Low

Meaning
Catalyst System Efficiency Below Threshold (Bank 2)
System
Emission Controls · Powertrain
Safe to drive?
Yes, short term
Typical repair cost
$150–$3,000
DIY difficulty
Moderate

P0430 only exists on engines with two cylinder banks, each with its own catalytic converter and its own pair of O2 sensors: V6 and V8 engines, flat engines, and some straight-sixes whose exhaust manifold is split into two groups. Bank 2 is the side that does NOT contain cylinder #1. The ECU runs the same oxygen-storage test as on bank 1, comparing the front and rear sensor on that side. The big diagnostic advantage is that bank 1 acts as a built-in reference: if bank 1 passes and only bank 2 fails, the fault is local to that side (its converter, its sensors, its manifold or one of its cylinders), not something shared like fuel quality or the engine computer.

Can I keep driving? You can normally keep driving while you sort it out. If the light starts flashing or you hear a new ticking from one side of the engine, get it looked at promptly: a misfiring bank 2 cylinder or a manifold leak will keep damaging that converter.

How to read P0430

How to read P0430P10243304
  1. P Powertrain
  2. 0 Generic (SAE)
  3. 4 Auxiliary emission controls
  4. 30 Specific fault

Symptoms

  • Check engine light with no change in how the engine runs
  • Ticking from one side of the engine at cold start that fades as it warms up (manifold leak)
  • Rattle from the bank 2 converter or front exhaust pipe
  • Failed smog or emissions test
  • Sulfur smell from the exhaust
  • Loss of power at higher rpm if the bank 2 converter is plugged

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Bank 2 catalytic converter aged, poisoned or internally damaged 40%
  2. Exhaust manifold leak on bank 2: cracked manifold, broken studs or blown gasket 20%
  3. Bank 2 rear O2 sensor slow or contaminated 15%
  4. Misfire or leaking injector on a bank 2 cylinder that overheated the converter 12%
  5. Oil consumption concentrated on one bank (valve seals, PCV routing) fouling that converter 8%
  6. O2 sensor connectors swapped between banks after an earlier repair 5%

Diagnosis step by step

Diagnostic flow: P04301Confirm which side is bank 22Compare both banks side by side3Check Mode 6 for both converters4Inspect the bank 2 manifold5Check misfire counts per cylinder6Verify sensor wiring and routing

  1. Confirm which side is bank 2

    Look up where cylinder #1 is; bank 2 is the opposite side. On Ford V8 trucks bank 1 is the passenger side, while on GM and Chrysler V8s it's the driver side, and transverse V6 engines vary by maker, so check before ordering parts.

    Tools: Flashlight

  2. Compare both banks side by side

    Graph all four O2 sensors on a warm engine at steady cruise. If bank 1's rear sensor stays calm while bank 2's rear sensor mirrors its front sensor, the bank 2 converter is weak. Also compare long-term fuel trims: a bank 2 trim far more positive than bank 1 points to an air leak or injector problem on that side.

    Tools: OBD-II scanner

  3. Check Mode 6 for both converters

    Pull the catalyst monitor results for bank 1 and bank 2. Seeing bank 1 comfortably inside its limit and bank 2 far outside it strongly supports replacing just the bank 2 converter.

    Tools: OBD-II scanner

  4. Inspect the bank 2 manifold

    On a cold engine, listen for ticking and look for soot marks at the manifold-to-head joint and the manifold-to-pipe flange. Broken or missing studs are common on some V8s and let air in right ahead of the sensors.

    Tools: Flashlight

  5. Check misfire counts per cylinder

    Many scan tools show misfire counters for each cylinder in Mode 6. Even a few misfires on one bank 2 cylinder can overheat that converter without setting a misfire code.

    Tools: OBD-II scanner

  6. Verify sensor wiring and routing

    Trace each O2 sensor harness back to its connector. Swapped connectors between banks cause confusing fuel trim and catalyst results and are easy to miss after previous exhaust work.

    Tools: Flashlight, Multimeter

Where the parts are

Exhaust: catalytic converter and O2 sensors (Bank 1 / Bank 2) – P04301212345
Exhaust: catalytic converter and O2 sensors (Bank 1 / Bank 2)
  1. 1Upstream O2 sensor
  2. 2Catalytic converter
  3. 3Downstream O2 sensor
  4. 4Diesel particulate filter
  5. 5Turbocharger

Repair options & costs

RepairDIY?Estimated cost
Replace bank 2 downstream O2 sensor Yes $150–$400
Repair bank 2 manifold leak or broken studs No $300–$1,200
Aftermarket EPA-compliant bank 2 converter No $450–$1,400
OEM or CARB-approved bank 2 converter or converter/pipe assembly No $1,000–$3,000

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Notes by brand

Ford

Ford V8 trucks and SUVs, notably the 5.4L three-valve in the F-150 and Expedition, are known for broken exhaust manifold studs; the resulting leak ticks at cold start and can skew the downstream O2 reading. On Ford V8s, bank 1 is the passenger side.

P0430 on Ford in detail

Chevrolet

GM V8s have cylinder #1 on the driver side, so bank 2 is the passenger side on a Silverado, Tahoe or Camaro V8.

BMW

Many BMW straight-six engines split the exhaust into cylinders 1–3 and 4–6, each with its own converter and sensors, so they can set P0430 even though they have only one row of cylinders.

Field data

Honda 47 Pilot, Odyssey, Ridgeline
Ford 15
Nissan 5 Altima, Pathfinder, QX56
Chevrolet 4 Avalanche, Captiva, Suburban 1500
Dodge 4 Durango, Charger Srt
Jeep 4 Cherokee, Commander, Compass
GMC 3 Acadia, Yukon Xl
Toyota 2 Corolla, Tacoma

Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.

Emissions / smog test impact

Will fail

An active P0430 with the check engine light on fails an OBD-based emissions or smog test. After a repair, drive until the catalyst monitor reports 'ready' before going back, because most states allow only one incomplete monitor on 2001-and-newer vehicles.

Frequently asked questions

Which side of the engine is bank 2?

Bank 2 is the side without cylinder #1. On Ford V8s that's the driver side; on GM and Chrysler V8s it's the passenger side. Transverse V6 engines differ by manufacturer, so check the cylinder numbering for your engine.

I have both P0420 and P0430 — are both converters bad?

Not necessarily. When both banks fail together, look for a shared cause first: oil burning, a rich-running fuel system, an aftermarket tune or simply two original converters at high mileage. When only P0430 is set, the problem is almost always on that one side.

Can a four-cylinder engine set P0430?

An ordinary inline four has only bank 1, so it should never set a genuine P0430. If you see it on one, re-scan with another tool and check that the code was read from the engine computer.

Can I replace only the bank 2 converter?

Yes, if bank 1 passes its monitor. On some trucks both converters are part of one Y-pipe assembly, so you may have to buy the complete section.

Is the bank 2 converter covered by the emissions warranty?

The same federal 8-year/80,000-mile coverage for catalytic converters applies to both banks. If you're within that window, have the dealer confirm the failure before paying anyone else.

Sources