Same as P0420 but on the bank 2 (passenger) cylinder bank — V6 / V8 engines only.
P0430 — also written PO43O, P 0430, 0430 — is the OBD-II code for catalyst system efficiency below threshold (bank 2). Same code, same fix: this page covers every spelling of it.
Catalyst efficiency below threshold on bank 2 — same fault as P0420 but on the passenger-side cylinder bank of a V6 or V8. The rear (post-cat) lambda is mirroring the front sensor too closely, which tells the ECU the cat isn't scrubbing exhaust gases properly. In UK workshops this is almost always Land Rover/Jaguar V6/V8, Nissan/Infiniti VQ35, Ford Mondeo/S-Max 2.5 V6, Lexus IS/GS and older BMW/Mercedes petrol V6s past 100k.
P0430 is a emissions fault code, typically costing £180–£1400 to put right in a UK garage.
What P0430 actually feels like to drive
- MIL comes on after a motorway run then stays lit — no drivability change
- Slight sulphur/rotten-egg smell on hard acceleration
- MPG drop of 1–3 mpg you wouldn't notice unless you track it
- Fails emissions/lambda snapshot at MOT despite passing tailpipe CO
- Bank 2 short-term fuel trim slightly richer than bank 1 at cruise
What causes P0430?
- Worn bank 2 catalytic converter
- Failed bank 2 rear O2 sensor
- Exhaust leak before bank 2 cat
- Bank-specific misfire
UK vehicles that throw P0430 most often
- Land Rover Discovery 3/4 & Range Rover Sport 4.4 V8 / 3.0 V6 petrol
- Jaguar XF / XJ / F-Type 3.0 V6 supercharged petrol
- Nissan 350Z / 370Z / Infiniti G37 (VQ35/VQ37) — bank 2 rear lambda notorious
- Ford Mondeo ST220 / S-Max 2.5 V6 (Duratec 30)
- Lexus IS250 / GS300 / RX350 — bank 2 catalyst monolith cracking
- BMW 5 Series N62 4.4 V8 / older Mercedes M272 3.5 V6
- Vauxhall Vectra / Signum 3.2 V6 (Alloytec)
How P0430 is fixed
- Same diagnostic as P0420 but bank 2 side
- Replace bank 2 rear lambda first as trial
- Confirm with lambda graphing before cat replacement
The P0430 misdiagnosis that wastes money
Nine garages out of ten quote a rear catalytic converter on bank 2 as the first move — and on a Land Rover V8 or Jag V6 that's a £1,400–£2,600 bill. Don't touch the cat until you've done three checks. One — swap the front (upstream) lambdas bank-to-bank and clear the code; if the fault moves to bank 1 you've got a tired front sensor giving the ECU a bad reference, not a dead cat. Two — check for an exhaust manifold leak on bank 2. On Land Rover 4.4 V8 the manifold-to-downpipe gasket blows and pulls fresh air into the exhaust ahead of the rear sensor, which mimics a failed cat perfectly. Three — read live fuel-trim on bank 2: if long-term fuel trim is stuck at +10% or higher, you've got an intake vacuum leak or a fuel-pressure issue on that bank, not a cat problem. Only after those three tests do you consider a rear cat — and even then a JLM catalyst cleaner + a 40-minute high-load Italian tune-up recovers a marginal cat around one time in three.
What a UK garage should charge for P0430
Diagnostic + swap-and-relearn lambda test £60–£90, exhaust manifold gasket bank 2 £180–£420, front lambda (upstream) bank 2 replacement £110–£220 fitted with OE-spec, rear (downstream) lambda bank 2 £95–£190, rear catalytic converter bank 2 £480–£1,600 independent / £1,400–£2,800 main dealer on JLR and Lexus. Labour From £70/hr at Bob's. If a garage quotes a cat without a documented bank-swap test, get a second opinion.
P0430 repair cost in the UK
Most P0430 repairs land between £180–£1400 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0430
The single fastest way to prove P0430 is the sensor or the cat: buy a £15 O2-simulator dongle (or ask the garage to fit a mini-cat 'lambda spacer' as a diagnostic) — if the code clears and stays clear the rear cat is fine and the ECU was just seeing a slightly slow sensor. On JLR V8s always check the coolant crossover pipe under the manifold first — a small coolant leak drops the cat temperature just enough to trigger P0430 without any obvious external puddle. Not sure whether it's a £95 sensor, a £250 manifold gasket or a £1,500 cat on your V6/V8? <a href="/ask-a-mechanic-uk?code=P0430">Ask Bob about your P0430</a> for £14.99 with make, model, mileage and any bank-1 codes stored alongside — you'll get the right test order before you spend a penny on parts.
Can you drive with P0430?
Yes, short term — but expect MOT emissions failure.
Urgency: medium.