The Quick Answer above is the generic definition. What follows is the model-specific detail for the BMW models that log P2188.
DTC/P2188·BMW
P2188 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)BMW
P2188 on a BMW means the engine is running too rich specifically at idle on Bank 1, meaning too much fuel relative to the amount of air entering the engine at low RPM. The ECU has detected that it cannot reduce fuel delivery enough to maintain the correct air-fuel ratio while idling.
Typical repair cost, all makes€35 - €400
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BMW 3 Series
2005-2024The E90 with the N52 uses port injection, so a rich Bank 1 there usually traces to a leaking port injector or a faulty fuel pressure sensor. The E90/F30 with the direct-injected N55 can set P2188 from a leaking injector, and its high-pressure fuel pump can overdeliver at idle, creating a rich condition. The VANOS system can also cause rich running on either engine if the intake camshaft timing is advanced too far.
What causes P2188 on a BMW?
Beyond the generic causes listed on the main P2188 page, these are the patterns noted for BMW models:
BMW 3 SeriesLeaking fuel injector, direct injection on the N55 or port injection on the N52
BMW 3 SeriesHigh-pressure fuel pump overdelivery on N55
BMW 3 SeriesVANOS intake camshaft over-advance at idle
How to diagnose P2188 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P2188:
- Check short-term and long-term fuel trims at idle with a scanner. Negative values (below -10%) confirm the ECU is trying to reduce fuel. If trims return to normal at higher RPM, the issue is idle-specific.
- Check for a leaking fuel injector. Do not open a pressurised fuel rail to look for drips. Fit a fuel pressure gauge, run the engine until pressure is stable, then switch off and watch the gauge. Pressure that bleeds away over the next few minutes points to a leaking injector or a failed check valve in the pump, and a workshop can then isolate which cylinder is at fault.
- Check the MAF sensor reading at idle. If the sensor reports higher airflow than actual, the ECU will deliver excess fuel. Clean the MAF with dedicated sensor cleaner or compare readings to known-good values.
- Measure fuel pressure at idle. Higher than specification pressure forces excess fuel through the injectors even at normal duty cycle. The fuel pressure regulator may be stuck or its vacuum reference line disconnected.
- Check the EVAP purge valve by disconnecting its vacuum hose at idle. If the idle improves and fuel trims move toward zero, the purge valve is stuck open and allowing excess fuel vapour into the intake.
How much does P2188 cost to fix on a BMW? (EUR)
Estimated repair costs for P2188 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 P2188
These codes are often seen alongside P2188 or point to related issues, on any make:
Looking for the full P2188 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P2188 guideSkanyx · BMW
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