What Does P2187 Mean?
The PCM is adding excessive fuel (positive long-term fuel trim) at idle to compensate for a lean condition on Bank 1. The air/fuel mixture contains too much air or insufficient fuel at idle speeds only.
Common Causes
40%
Vacuum leak in intake manifold, brake booster, or PCV system
25%
Dirty or failing mass airflow (MAF) sensor reading low airflow
20%
Fuel pressure too low or weak fuel pump
10%
Clogged or restricted fuel injectors on Bank 1
5%
Exhaust leak before oxygen sensor affecting readings
Diagnostic Steps
1
Step 1: Check fuel trim values at idle (LTFT and STFT); values over +15% confirm lean condition; compare to higher RPM readings
2
Step 2: Perform smoke test or propane enrichment test around intake manifold, throttle body, and vacuum lines to locate air leaks
3
Step 3: Inspect MAF sensor for contamination; clean with MAF cleaner or test voltage/frequency output against specifications
4
Step 4: Connect fuel pressure gauge and verify pressure meets specifications at idle (typically 35-60 PSI depending on system)
5
Step 5: Check for exhaust leaks before upstream O2 sensor; inspect PCV valve and hoses for proper operation
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
The PCM is adding excessive fuel (positive long-term fuel trim) at idle to compensate for a lean condition on Bank 1. The air/fuel mixture contains too much air or insufficient fuel at idle speeds only.
The most common cause of P2187 (System Too Lean at Idle Bank 1) is: Vacuum leak in intake manifold, brake booster, or PCV system
Typical repair costs for P2187 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive but may experience rough idle, hesitation, or stalling at stops. Extended driving with lean condition can damage catalytic converter and cause engine overheating.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2187 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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