The Quick Answer above is the generic definition. What follows is what is documented for the Mercedes-Benz models that log P0422, checked against manufacturer data and owner reports.
DTC/P0422·Mercedes-Benz
P0422 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0422 on a Mercedes-Benz 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.
Repair cost on Mercedes-Benz€105 - €1660
Connect any standard Bluetooth OBD2 adapter to your Mercedes-Benz and Skanyx tells you what P0422 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
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Mercedes-Benz E-Class
2009-2024On 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.
What causes P0422 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0422 page, these are the documented Mercedes-Benz-specific patterns:
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
How to diagnose P0422 on a Mercedes-Benz with OBD2
Follow these steps to pinpoint the root cause of 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
How much does P0422 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0422 in EUR, compiled across makes. Expect Mercedes-Benz parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0422 on Mercedes-Benz
These codes commonly cluster with P0422 on Mercedes-Benz vehicles:
Looking for the full P0422 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0422 guideSkanyx · Mercedes-Benz
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