Fault-Code Library · Fuel mixture
P2187: System too lean at idle, bank 1
The ECU detects a lean condition mainly at idle, where small air leaks have a larger effect on mixture control.
Common symptoms
- •Rough idle
- •Stalling
- •Whistling noise
- •Hesitation leaving idle
Likely causes
- •PCV diaphragm leak
- •Vacuum hose leak
- •Intake manifold leak
- •Purge valve stuck open
First checks
- •Compare fuel trims at idle and raised RPM
- •Smoke-test the intake and PCV system
- •Check purge valve sealing
Important
Idle-only lean faults are usually diagnosed faster with smoke testing than with parts swapping.
A fault code identifies a detected condition, not a failed part. Confirm manufacturer-specific subcodes and live data.
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