The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0170.
DTC/P0170·Mercedes-Benz
P0170 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0170 on a Mercedes-Benz means the fuel trim values on bank 1 have exceeded the normal correction range. The ECU can no longer properly compensate for a rich or lean condition by adjusting fuel delivery. This indicates a persistent air-fuel mixture problem that needs investigation.
Typical repair cost, all makes€20 - €500
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Mercedes C-Class
2007-2024The M271 and M274 engines can develop intake manifold swirl flap issues that cause vacuum leaks and trigger P0170. The M274 2.0T is also sensitive to MAF sensor contamination. Include the crankcase ventilation system in the diagnosis, because a split breather hose or a failed pressure regulating valve shifts the mixture the same way a manifold leak does.
What causes P0170 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0170 page, these are the patterns noted for Mercedes-Benz models:
Mercedes C-ClassIntake manifold swirl flap failure on M271/M274 engines
Mercedes C-ClassCrankcase ventilation valve failure causing positive fuel trims
How to diagnose P0170 on a Mercedes-Benz with OBD2
Follow these steps to pinpoint the root cause of P0170:
- Use a scan tool to read short-term and long-term fuel trims for bank 1. Values beyond +/- 25% indicate a significant air-fuel ratio problem. Positive trims mean lean, negative trims mean rich
- If fuel trims are positive (lean), perform a smoke test or propane enrichment test to find vacuum leaks. Check intake manifold gaskets, PCV hoses, brake booster line, and all vacuum connections
- Inspect and clean the MAF sensor with dedicated MAF cleaner spray. A contaminated MAF underreports airflow, causing lean fuel trims
- Check fuel pressure with a gauge. Low pressure causes lean trims, high pressure causes rich trims. Compare to manufacturer specifications
- Monitor the upstream O2 sensor data. If it is sluggish or stuck, it may be providing incorrect feedback that forces the fuel trims out of range
- If trims are negative (rich), check for leaking injectors by performing a fuel injector balance test or checking for fuel smell in the oil
How much does P0170 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0170 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.
Codes related to P0170
These codes are often seen alongside P0170 or point to related issues, on any make:
Looking for the full P0170 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0170 guideSkanyx · Mercedes-Benz
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