System Too Lean at Idle (Bank 1)
The P2187 code means the vehicle's onboard diagnostic system has detected: System Too Lean at Idle (Bank 1). This is a serious severity code.
- Keep driving?
- Limited driving only
- DIY difficulty
- medium
- Estimated cost
- $0-$50 for vacuum hose repair; $0 for cleaning
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What Are the Symptoms of P2187?
- Rough idle only (normal at higher RPM)
- Check Engine Light on
- Stalling at idle
What Causes P2187? (Most Likely First)
- Small vacuum leak that only affects idle (high RPM masks it) Very High
- Dirty IAC valve or carbon-restricted throttle body idle port High
- Clogged idle air passage Moderate
Can I Still Drive with P2187?
Limited driving only. P2187 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Common Fixes by Vehicle
What techs usually find when diagnosing P2187 on specific vehicles — tap your vehicle for the fix and the exact part:
2009-2017 VW GTI/Jetta/Audi A4 2.0T TSI moderate DIY
VW 2.0T TSI P2187 is almost always the PCV valve built into the valve cover. The diaphragm tears, creating a huge idle vacuum leak. Replace the entire valve cover assembly (06K 103 469 AC for EA888 Gen3). Smoke test after install to verify all leaks are fixed.
Labor: 2-3 hours2014-2019 Mazda3/6/CX-5 2.0L/2.5L SkyActiv easy DIY
Mazda SkyActiv P2187 points to a vacuum leak from the intake manifold gasket or a torn PCV hose. Smoke test at idle. Common failure: hairline crack at the PCV elbow on top of the valve cover (Mazda). Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 30 min2005-2015 Ford Focus/Fusion 2.0L/2.5L easy DIY
Check the brake booster check valve and hose -- a cracked check valve causes a big idle vacuum leak that only shows at idle (P2187) because at cruise the manifold vacuum drops and masks it. $10 fix with a Dorman or Motorcraft replacement.
Labor: 15 minFrequently Asked Questions
What makes P2187 different from P0171?
P0171 (lean Bank 1) is triggered based on long-term fuel trim across all operating conditions. P2187 is specifically triggered at idle only. This distinction helps narrow the cause to issues that primarily affect idle: small vacuum leaks or restricted idle passages.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P2187?
-
Monitor STFT (short-term fuel trim) at idle. Large positive values confirm lean condition at idle only.
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Rev the engine to 2,000 RPM and check STFT: if it normalizes at higher RPM, the leak is small and only significant at idle.
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Search for small vacuum leaks using a smoke machine. Small leaks invisible to the eye show up clearly.
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Clean the throttle body idle bypass ports and IAC valve.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Which Vehicles Commonly Get P2187?
- Volkswagen Jetta and Passat (common idle vacuum issues)
- Audi A4 and A6
- BMW 3 and 5 Series
- Subaru Outback and Forester
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