The Quick Answer above is the generic definition. What follows is the model-specific detail for the BMW models that log P2187.
DTC/P2187·BMW
P2187 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)BMW
P2187 on a BMW means the engine is running too lean specifically at idle speed on Bank 1. The fuel system is not delivering enough fuel relative to the amount of air entering the engine at low RPM. This is different from P0171, which indicates a lean condition across all operating ranges.
Typical repair cost, all makes€35 - €380
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BMW 3 Series
2005-2024On the E90 with the naturally aspirated N52, unmetered air at idle often comes from the crankcase ventilation system, the oil filler cap seal or the dipstick tube seal, and higher-output N52 versions also have a DISA intake valve whose seal can leak. The turbocharged N55 has no DISA valve, so on those cars look at the crankcase ventilation, the intake and the charge pipes instead.
What causes P2187 on a BMW?
Beyond the generic causes listed on the main P2187 page, these are the patterns noted for BMW models:
BMW 3 SeriesCrankcase ventilation (CCV) system leak on N52
BMW 3 SeriesDISA valve seal leak on higher-output N52
BMW 3 SeriesOil filler cap gasket and dipstick tube leaks
How to diagnose P2187 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P2187:
- With the engine idling, listen carefully for any hissing or whistling sounds around the intake manifold, vacuum hoses, and PCV system. A vacuum leak is a usual cause and is often audible.
- Use a smoke machine to pressurize the intake system and find vacuum leaks. Smoke will escape from any crack, split hose, or faulty gasket. Pay special attention to the intake manifold gasket and brake servo hose.
- Check the MAF sensor readings at idle using live data. Compare the actual airflow reading to the manufacturer's specification for your engine. A dirty MAF sensor will underreport airflow, causing the ECU to deliver too little fuel.
- Monitor short-term and long-term fuel trims at idle. Values above +10% confirm the ECU is adding fuel to compensate for a lean condition. If trims normalise at higher RPM, the leak is only significant at idle vacuum.
- If no vacuum leak or MAF issue is found, check fuel pressure at idle with a fuel pressure gauge. Low fuel pressure at idle but normal pressure at higher RPM can indicate a failing fuel pressure regulator or weak fuel pump.
How much does P2187 cost to fix on a BMW? (EUR)
Estimated repair costs for P2187 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.
Codes related to P2187
These codes are often seen alongside P2187 or point to related issues, on any make:
Looking for the full P2187 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P2187 guideSkanyx · BMW
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