What does P2187 mean?
The computer constantly adjusts how much fuel it adds based on the oxygen sensors. This code means it has reached the limit of its correction on bank 1 at idle.
A lean code means the engine is getting more air than the fuel being delivered. Either air is getting in that the computer did not measure, or fuel delivery is falling short.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light
- Rough or unstable idle
- Hesitation when accelerating
- Lower fuel economy
- Sometimes misfire codes too
Common causes
- Vacuum leak (cracked hose, intake gasket, PCV valve or hose)
- Dirty or failing MAF sensor reading low
- Low fuel pressure (weak pump, clogged filter, bad regulator)
- Clogged or leaking fuel injectors
- Exhaust leak ahead of the upstream O2 sensor
- On idle-only lean codes, small vacuum leaks are the usual suspect because they matter most at low airflow
How to diagnose P2187
- Look at long-term fuel trim. Readings above about +10% at idle point to a lean condition.
- If trims are high at idle and improve at 2,500 rpm, suspect a vacuum leak. If they get worse at higher rpm, suspect fuel delivery or the MAF.
- Smoke-test the intake for leaks.
- Check fuel pressure against spec.
- Clean the MAF sensor and recheck.
How to fix it
- Repair vacuum or intake leaks
- Clean or replace the MAF sensor
- Replace the PCV valve or hose
- Repair fuel pressure problems (pump, filter, regulator)
- Clean or replace injectors
Estimated repair cost
Likely repairs for P2187 run from about $20 to $1,300, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Diagnostic fee (scan + testing) | $100 - $200 |
| Vacuum leak repair (hose/gasket) | $100 - $450 |
| PCV valve / hose replacement | $50 - $300 |
| MAF sensor cleaning | $20 - $100 |
| Mass airflow sensor replacement | $150 - $450 |
| In-tank fuel pump (gasoline) | $500 - $1,300 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P2187?
Moderate severity
You can usually drive it short term, but a lean engine can misfire and run hot, so fix it soon.
P2187 FAQ
What does P2187 mean?
P2187 stands for "System Too Lean at Idle (Bank 1)". The computer constantly adjusts how much fuel it adds based on the oxygen sensors.
Can I drive with a P2187 code?
You can usually drive it short term, but a lean engine can misfire and run hot, so fix it soon.
How much does it cost to fix P2187?
It depends on the cause. The likely repairs for P2187 range from about $20 to $1,300 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P2187?
The most common causes are: vacuum leak (cracked hose, intake gasket, PCV valve or hose); dirty or failing MAF sensor reading low; low fuel pressure (weak pump, clogged filter, bad regulator).