The Quick Answer above is the generic definition. What follows is what is documented for the BMW models that log P0173, checked against manufacturer data and owner reports.
DTC/P0173·BMW
P0173 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)BMW
P0173 on a BMW means the ECU has pushed long-term fuel trim on Bank 2 to the limit of its correction range and still cannot maintain the target air-fuel ratio. Because P0173 only affects one bank, it usually points to something specific to Bank 2 (a leak, a degraded sensor, or a dirty injector on that bank) rather than a whole-engine issue like a clogged fuel filter that would affect both banks.
Repair cost on BMW€70 - €420
Connect any standard Bluetooth OBD2 adapter to your BMW and Skanyx tells you what P0173 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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BMW 3 Series
2006-2024335i and 335d with the N54 inline-six are technically single-bank engines, but BMW V8 M3 (E92) and 6-cylinder V configurations historically logged P0173 with HPFP-related rough running. On modern N55/B58 inline applications P0173 is rare; on legacy V8 3 Series it typically traces to one side's pre-cat lambda sensor degrading first.
What causes P0173 on a BMW?
Beyond the generic causes listed on the main P0173 page, these are the documented BMW-specific patterns:
BMW 3 SeriesUpstream lambda sensor degradation on legacy V8 3 Series
BMW 3 SeriesCarbon on Bank 2 intake valves on direct injection variants
How to diagnose P0173 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0173:
- Read live data: focus on short-term and long-term fuel trim for Bank 2. A long-term trim above +20% or below -20% confirms the bank has been hitting its limits
- Compare Bank 2 trims to Bank 1. If only Bank 2 is out of range, the cause is bank-specific (one injector, one sensor, one manifold gasket section)
- Smoke-test the intake on Bank 2 specifically. On V engines, intake manifold gaskets fail one side at a time as plastic shrinks unevenly
- Swap the upstream sensors between banks and re-check live data. If the high trim follows the sensor, replace it; if it stays on the original bank, focus on mechanical causes
- Inspect for exhaust leaks ahead of the Bank 2 upstream sensor. A small leak can pull fresh air into the exhaust stream and trick the sensor into reading lean
How much does P0173 cost to fix on a BMW? (EUR)
Estimated repair costs for P0173 in EUR, compiled across makes. Expect BMW 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 P0173 on BMW
These codes commonly cluster with P0173 on BMW vehicles:
Looking for the full P0173 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0173 guideSkanyx · BMW
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