P0172: System Too Rich (Bank 1)
11 vehicles · 9 makes · $50-$2,800 repair
Most Reported On
P0172 is an OBD-II diagnostic trouble code meaning “System Too Rich (Bank 1).” P0172 means the engine computer has determined the air/fuel mixture on bank 1 is too rich — there is too much fuel relative to air. The PCM watches the oxygen sensors and fuel trims; when it must repeatedly cut back fuel to compensate for an over-rich condition and hits its correction limit, it sets this code. Bank 1 is the side of the engine containing cylinder number one. You may notice poor fuel economy, rough idle, a sulfur/rotten-egg smell, black exhaust smoke, or fouled spark plugs. This code is most commonly reported on 2022-2024 Jeep Grand Wagoneer, 2008-2011 Buick Enclave, and 2017-2018 Honda CR-V, plus 8 other vehicles, with repair costs ranging from $50 to $2,800.
Common Causes
Typical Repair Cost
Based on 12 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0172, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (11)
CSFI 'Spider' Central Port Injector / Poppet Valve Failure (5.7L Vortec)
5.7L Vortec CSFI 'Spider' Poppet Injector Failure
CSFI "spider" poppet fuel injector failure (special coverage 99066F)
FAQ
What does P0172 mean?
P0172 stands for "System Too Rich (Bank 1)." P0172 means the engine computer has determined the air/fuel mixture on bank 1 is too rich — there is too much fuel relative to air. The PCM watches the oxygen sensors and fuel trims; when it must repeatedly cut back fuel to compensate for an over-rich condition and hits its correction limit, it sets this code. Bank 1 is the side of the engine containing cylinder number one. You may notice poor fuel economy, rough idle, a sulfur/rotten-egg smell, black exhaust smoke, or fouled spark plugs.
What are the most common causes of P0172?
The most common causes of P0172 are: Dirty or faulty mass airflow (MAF) sensor, Leaking or stuck fuel injector, High fuel pressure (faulty regulator), Faulty oxygen sensor giving skewed readings, Clogged or dirty air filter, Leaking evaporative purge valve adding fuel vapor, Engine coolant temperature sensor reading too cold, Worn spark plugs causing inefficient combustion. The specific cause varies by vehicle.
How much does it cost to fix P0172?
Repair costs for P0172 range from $50 to $2,800, depending on the vehicle and root cause.
Which vehicles are affected by P0172?
Au7o has documented P0172 across 11 vehicle models from 9 manufacturers: Buick, Chevrolet, GMC, Honda, Jeep, Kia, Nissan, Ram, Volvo.
Sources (12)
- TSBGM Preliminary Information PI0746 - PCV, Ice and Oil Deposits
- TSBWarranty Extension TSB 19-032 — 2017-18 CR-V: Software Update with A/C Control Unit Replacement; DTC P0300-P0304/P0172 (NHTSA bulletin PDF)
- articleJudge Approves Honda Oil Dilution Class Action Settlement (2017-2018 CR-V & 2016-2018 Civic 1.5T)
- Forum2018 Honda CR-V Fuel In Oil With Overfilled Oil Level, Gas Smell In Cabin (CarComplaints — 63 complaints)
- videoYouTube - How to Replace Fuel Pressure Regulator on 1996 GMC Jimmy - ChrisFix
- ForumReddit r/MechanicAdvice Thread Discussing Oil Dilution in Kia Telluride 3.8L V6
- articleGMC/Chevy Light Truck: Central Port Fuel Injection Diagnosis - UnderhoodService
- Forum97 5.7 Vortec - injectors and poppet/spider issue - Chevrolet Forum
- Forum97 5.7 Vortec Injectors and Poppet/Spider Issue - Chevrolet Forum (Suburban)
- articleHow To Test the 'Spider' Fuel Injector Assembly (5.7L) - TroubleshootMyVehicle
- articleLiving Under the Hood: Diagnosing Central Port Fuel Injection
- ForumMisfire and Hard Start Troubles [SOLVED - fuel pressure damper] - NICOclub
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.