DTC/P0422

P0422: Main Catalyst Efficiency Below Threshold (Bank 1)

Quick Answer

Moderata GravitàSicuro da guidare (a breve termine)Emissioni

P0422 means the main catalytic converter on Bank 1 has dropped below the efficiency threshold the ECU expects. It is similar to P0420 but used on some manufacturers (notably Chrysler, Jeep, and certain European platforms) to distinguish the main cat from the upstream warm-up cat in multi-brick exhaust systems.

Costo di riparazione stimatoDa €105 a €1660+, varia in base al veicolo

Cosa significa P0422?

P0422 è un codice diagnostico di guasto relativo a emissioni, classificato con gravità moderate. Quando la centralina (ECU) del tuo veicolo rileva questa condizione, memorizza P0422 e accende la spia motore.

Quali sono i sintomi di P0422?

Se il tuo veicolo ha attivato P0422, potresti notare uno o più di questi sintomi:

Check engine light illuminated
Slight drop in fuel economy
Rotten-egg sulfur smell from exhaust
Possible rattling from under the car (substrate breaking up)
Failed emissions or periodic technical inspection

Cosa causa P0422?

Ecco le cause più comuni di P0422, ordinate in base alla probabilità che siano la causa del problema:

altaFailing or worn main catalytic converter (Bank 1)

mediaFaulty downstream O2 sensor (Bank 1, Sensor 2) with sluggish switching

mediaExhaust leak between pre-cat and main cat or after the main cat

bassaPrior misfire damaging the main converter brick

bassaOil or coolant consumption fouling the substrate

È sicuro guidare con P0422?

In genere sì, per brevi tragitti. Safe for normal driving. The check engine light will prevent emissions or periodic technical inspection passage. If the code is accompanied by rattling under the floor, the converter substrate may be breaking apart internally and replacement should be prioritised.

Come si diagnostica P0422?

Segui questi passaggi per individuare la causa principale di P0422:

Read freeze frame data and check for companion catalyst codes (P0420, P0421) that may be active at the same time
Inspect the full Bank 1 exhaust run for leaks, especially at flange joints and slip-fit connectors after the main cat
Graph the Bank 1 downstream O2 sensor at steady 2,000 to 2,500 RPM. A healthy main cat keeps it stable around 0.4 to 0.6 V
If the downstream signal swings more than 0.2 V repeatedly, the main cat is no longer storing oxygen and is failing
Test downstream sensor switching speed. Anything over 300 ms is sluggish and may be the actual fault

Quanto costa riparare P0422?

I costi di riparazione di P0422 variano a seconda della causa principale e del tuo veicolo. Ecco le stime tipiche:

Riparazione	Costo dei ricambi	Costo della manodopera	Stima totale	Difficoltà fai-da-te
Replace main catalytic converter (Bank 1)	€220–€1400	€90–€260	€310–€1660	Professionale
Replace downstream O2 sensor (Bank 1)	€55–€160	€60–€130	€115–€290	Moderata
Fix exhaust leak (gasket or pipe section)	€25–€120	€80–€220	€105–€340	Moderata

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

P0422 su veicoli specifici

P0422 si comporta in modo diverso a seconda del tuo veicolo. Seleziona la tua auto qui sotto per cause specifiche del modello, problemi noti e stime dei costi adeguate:

BMW

P0422 su BMW 3 Series

2006-2024

P0422 on BMW 3 Series with N52, N55, or B58 inline-6 engines typically points to the main underfloor cat rather than the manifold-mounted pre-cat. On these engines, the main cat is a separate unit that is easier and cheaper to replace than the integrated pre-cat. Check for VANOS rich-running history because long-term overfuelling will kill the main cat well before 200,000 km.

Cosa causa P0422 su una BMW 3 Series?

BMW 3 SeriesUnderfloor main cat degradation, often after VANOS-related rich running

BMW 3 SeriesFailing fuel injector causing intermittent enrichment on Bank 1

Costo di riparazione di P0422 per BMW 3 Series

Costi stimati per i proprietari di BMW 3 Seriesadeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici BMW

Riparazione	Costo dei ricambi	Costo della manodopera	Stima totale	Difficoltà fai-da-te
Replace main catalytic converter (Bank 1)	€308–€1960	€126–€364	€434–€2324	Professionale
Replace downstream O2 sensor (Bank 1)	€77–€224	€84–€182	€161–€406	Moderata
Fix exhaust leak (gasket or pipe section)	€35–€168	€112–€308	€147–€476	Moderata

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Volkswagen

P0422 su Volkswagen Golf

2005-2024

On Golf TSI and TFSI models with the EA888 engine, the main cat sits in the underfloor section after the pre-cat. P0422 typically shows up at 180,000 to 220,000 km on healthy engines. If the car has any history of P0171 lean codes or P0300 misfires, the main cat will fail earlier. Always inspect the flex pipe upstream of the main cat for cracks because a small exhaust leak there mimics catalyst failure.

Cosa causa P0422 su una Volkswagen Golf?

Volkswagen GolfEA888 main cat end-of-life around 200,000 km

Volkswagen GolfCracked flex pipe upstream creating false catalyst efficiency reading

Costo di riparazione di P0422 per Volkswagen Golf

Costi stimati per i proprietari di Volkswagen Golfadeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici Volkswagen

Riparazione	Costo dei ricambi	Costo della manodopera	Stima totale	Difficoltà fai-da-te
Replace main catalytic converter (Bank 1)	€253–€1610	€103–€299	€357–€1909	Professionale
Replace downstream O2 sensor (Bank 1)	€63–€184	€69–€150	€132–€334	Moderata
Fix exhaust leak (gasket or pipe section)	€29–€138	€92–€253	€121–€391	Moderata

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Audi

P0422 su Audi A6

2005-2024

The Audi A6 3.0 TFSI (EA837) and 3.0 TDI run separate main cats per bank. On Bank 1 (passenger side), the main cat is typically the first underfloor brick. P0422 here is often related to oil burning past the PCV system or, on TDI variants, soot loading from a stuck-open EGR valve. Check EGR operation before condemning the cat on diesel A6 variants.

Cosa causa P0422 su una Audi A6?

Audi A6PCV oil ingestion fouling Bank 1 main cat on TFSI

Audi A6Stuck EGR valve causing soot loading on 3.0 TDI

Costo di riparazione di P0422 per Audi A6

Costi stimati per i proprietari di Audi A6adeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici Audi

Riparazione	Costo dei ricambi	Costo della manodopera	Stima totale	Difficoltà fai-da-te
Replace main catalytic converter (Bank 1)	€286–€1820	€117–€338	€403–€2158	Professionale
Replace downstream O2 sensor (Bank 1)	€72–€208	€78–€169	€150–€377	Moderata
Fix exhaust leak (gasket or pipe section)	€33–€156	€104–€286	€137–€442	Moderata

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Mercedes-Benz

P0422 su Mercedes-Benz E-Class

2009-2024

On W212 and W213 E-Class with M276 V6 or M278 V8, P0422 commonly appears at 180,000 km. The Bank 1 main cat sits in the underfloor section and is accessible without dropping the subframe, which keeps labour reasonable compared to the pre-cat job. Check for any history of M276 balance-shaft gear wear, since that engine class has a known rough-running pattern that accelerates cat aging.

Cosa causa P0422 su una Mercedes-Benz E-Class?

Mercedes-Benz E-ClassM276 balance-shaft gear wear accelerating catalyst aging

Mercedes-Benz E-ClassBank 1 main cat end-of-life around 180,000 km

Costo di riparazione di P0422 per Mercedes-Benz E-Class

Costi stimati per i proprietari di Mercedes-Benz E-Classadeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici Mercedes-Benz

Riparazione	Costo dei ricambi	Costo della manodopera	Stima totale	Difficoltà fai-da-te
Replace main catalytic converter (Bank 1)	€308–€1960	€126–€364	€434–€2324	Professionale
Replace downstream O2 sensor (Bank 1)	€77–€224	€84–€182	€161–€406	Moderata
Fix exhaust leak (gasket or pipe section)	€35–€168	€112–€308	€147–€476	Moderata

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Questi codici compaiono spesso insieme a P0422 o indicano problemi correlati:

P0420 P0421 P0432 P0136 P0141

Domande frequenti su P0422

What is the difference between P0420 and P0422?

Both indicate Bank 1 catalyst efficiency problems. P0420 is the generic OBD-II code used by most manufacturers. P0422 is used by some manufacturers (commonly Chrysler-Jeep and some European brands) to specifically label the main catalyst when the exhaust has a separate warm-up pre-cat and main cat. The diagnosis is essentially identical.

Will P0422 cause my car to fail an emissions inspection?

Yes. P0422 is a catalyst efficiency code and the check engine light alone is an automatic fail in most EU periodic technical inspections (TÜV in Germany, ITV in Spain, SKP in Poland, TA in Lithuania).

Should I try an O2 sensor before replacing the catalyst?

Yes, because the downstream O2 sensor is roughly five to ten times cheaper than the converter. If sensor switching is slow but other readings are normal, replacing the sensor first is the sensible step. About 20 to 30 percent of catalyst efficiency codes are actually sensor faults.

How long should a replacement main catalyst last?

An OEM main cat installed in a healthy engine should last 200,000 km or more. Aftermarket units vary widely. A cheap aftermarket cat may fail again within 40,000 to 80,000 km, especially if any underlying fuel-trim or oil-consumption issue was not addressed first.

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