CarFaultIQ

P2187

P2187: System Too Lean At Idle Bank 1

Updated Last reviewed December 26, 2026By CarFaultIQ Editorial Team

Verify with official recall databases, service records, a mechanic inspection, and local market data before relying on this summary.

At a glance

Quick diagnostic answer

Bank 1 is running too lean at idle, meaning the computer sees too much air or not enough fuel at idle.

SeverityModerate UrgencyUrgency not yet verified EvidenceSource notes available
OBD code
P2187
System/category
Fuel & Air Metering
Severity
Moderate
Structured severity term
Urgency
Urgency not yet verified
Can I drive?
Drive with caution
Usually driveable short-term if it only idles a little rough, but do not ignore stalling, fuel smell, or repeated hard starts.
Repair/cost band
$$ · Moderate
Often a moderate diagnostic repair because vacuum, fuel, EVAP, and sensor causes can look similar.
Vehicle applicability
Generic OBD-II code across many makes and models; confirm service information for the exact vehicle.
Current applicability note is free text

Computed rule output may be more cautious than stored content and is never used to soften safety-critical risks.

Short answer

P2187 usually means bank 1 is running too lean at idle, meaning the computer sees too much air or not enough fuel at idle. Usually driveable short-term if it only idles a little rough, but do not ignore stalling, fuel smell, or repeated hard starts. Start with vacuum leaks, intake hoses, the MAF signal, and EVAP purge behavior before replacing sensors.

SeverityModerateDrive?Drive with cautionRepairProfessional

Key takeaways

  • P2187 points to a detected condition, not an automatic parts order.
  • Usually driveable short-term if it only idles a little rough, but do not ignore stalling, fuel smell, or repeated hard starts.
  • Start with vacuum leaks, intake hoses, the MAF signal, and EVAP purge behavior before replacing sensors.
  • Use scan data and a visual inspection before replacing sensors.

At a glance

Question Short answer Next move
Can I drive? Usually driveable short-term if it only idles a little rough, but do not ignore stalling, fuel smell, or repeated hard starts. Keep trips short if it runs normally; stop if symptoms get worse.
Likely cost Often a moderate diagnostic repair because vacuum, fuel, EVAP, and sensor causes can look similar. Get a written diagnosis before buying parts.
Check first Start with vacuum leaks, intake hoses, the MAF signal, and EVAP purge behavior before replacing sensors. Start with the cheap visible checks.

Can I still drive with this?

Drive with caution

Usually driveable short-term if it only idles a little rough, but do not ignore stalling, fuel smell, or repeated hard starts.

SeverityModerate

Moderate

Diagnostic flow

  1. What it meansBank 1 is running too lean at idle, meaning the computer sees…
  2. Check this firstCheck for obvious vacuum leaks and cracked intake hoses.
  3. Likely causeVacuum leak
  4. Can you drive?Drive with caution

Reference retained — diagnostic guidance withheld

P2187 is not yet in the verified diagnostic catalogue

CarFaultIQ is preserving this historical code URL, but it does not yet have an authoritative Layer K definition and evidence chain for this code. Causes, severity, drivability and repair guidance are therefore intentionally withheld rather than inferred.

Use manufacturer service information or a qualified technician for the vehicle-specific definition. If braking, steering, overheating, oil-pressure, fuel-leak or fire-risk symptoms are present, treat the symptom itself as the safety signal.

Check the symptomBrowse verified OBD references

What it means

Bank 1 is running too lean at idle, meaning the computer sees too much air or not enough fuel at idle.

Common symptoms

  • Rough idle
  • Hard start
  • Whistling or hissing noise
  • Fuel smell in some cases

Likely causes

  • Vacuum leak
  • Dirty or faulty MAF sensor
  • EVAP purge valve stuck open
  • Weak fuel delivery
  • O2 sensor data issue

Diagnosis steps

  1. Check for obvious vacuum leaks and cracked intake hoses.
  2. Inspect and test the MAF signal.
  3. Check whether the purge valve is stuck open.
  4. Review fuel trims at idle and under light throttle.

What a mechanic should check

A mechanic should compare idle and off-idle fuel trims to separate vacuum leaks from fuel-delivery or sensor issues.

Vehicle applicability

Generic OBD-II code across many makes and models; confirm service information for the exact vehicle.

Repair actions / cost band

$$ · Moderate

Often a moderate diagnostic repair because vacuum, fuel, EVAP, and sensor causes can look similar.

P2187 — vehicles with official records naming this code

P2187 is named in NHTSA-published manufacturer communications or investigations for 1 vehicle family, including:

A code named in a manufacturer communication means the document refers to it for those vehicles. It is not a diagnosis of any car, and it does not mean the code is common on that vehicle.

Frequently asked questions

What does P2187 mean?

bank 1 is running too lean at idle, meaning the computer sees too much air or not enough fuel at idle.

Is P2187 safe to drive with?

Usually driveable short-term if it only idles a little rough, but do not ignore stalling, fuel smell, or repeated hard starts.

What should I check first?

Start with vacuum leaks, intake hoses, the MAF signal, and EVAP purge behavior before replacing sensors.

Continue exploring

Related codes

Known faults that trigger this code

Related symptoms

Keep going

Next diagnostic step

Check warning lights Use the dashboard light to decide what to do now. Trace the symptom Match what you can see, hear, smell, or feel. Find vehicle coverage Check model-year problem windows and related faults.

Source & evidence notes

  • What this is based on: generic OBD-II code references, EPA OBD background, and standard diagnostic practice.
  • This page is not based on complaint counts, repair-cost averages, or CarFaultIQ owner submissions.
  • Sources used: AutoZone P2187 reference; CarParts P2187 reference; US EPA OBD background.
  • URLs: https://www.autozone.com/diy/diagnostic-trouble-codes/p2187-system-too-lean-at-idle-bank-1-dtc; https://www.carparts.com/blog/p2187-code-system-too-lean-at-idle-bank-1/; https://19january2021snapshot.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd_.html.
  • Confirm the exact diagnosis with live scan data, the owner manual, or service information for the specific vehicle.