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P0172ModerateFuel System

P0172: System Too Rich (Bank 1)

Found on 7 vehicle models across 6 makes

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P0172 is an OBD-II diagnostic trouble code meaning “System Too Rich (Bank 1).” The engine is running rich on Bank 1 — too much fuel or not enough air. Opposite of P0171 lean condition. According to Au7o's database, this code appears across 7 vehicle models from 6 manufacturers. Full vehicle-specific causes and solutions at au7o.io.

7
Vehicles Affected
6
Makes
7
Related Issues

Common Causes

1Leaking fuel injector
2Faulty fuel pressure regulator
3Dirty MAF sensor reading low
4Stuck closed EVAP purge valve
5Faulty O2 sensor

Diagnostic Tools

To diagnose P0172, you'll need an OBD-II scanner. Here are our recommendations at every price point.

Budget Pick$10–$20

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
Check Price on Amazon
Best Value$90–$120

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)
Check Price on Amazon
Advanced$180–$230

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
Check Price on Amazon
Professional$350–$450

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
Check Price on Amazon

As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.

Vehicles Affected by P0172

Click any vehicle to see the full issue details, symptoms, and repair guide.

Related Codes

P0171System Too Lean (Bank 1)P0174System Too Lean (Bank 2)P0087Fuel Rail/System Pressure - Too LowP0088Fuel Rail/System Pressure - Too HighP0130O2 Sensor Circuit Malfunction (Bank 1, Sensor 1)P0131O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)P0135O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)P0136O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)

Frequently Asked Questions

What does P0172 mean?

P0172 stands for "System Too Rich (Bank 1)." The engine is running rich on Bank 1 — too much fuel or not enough air. Opposite of P0171 lean condition.

What are the most common causes of P0172?

The most common causes of P0172 are: Leaking fuel injector, Faulty fuel pressure regulator, Dirty MAF sensor reading low, Stuck closed EVAP purge valve, Faulty O2 sensor. The specific cause varies by vehicle — Au7o documents vehicle-specific causes for 7 models.

How much does it cost to fix P0172?

Repair costs vary widely depending on the root cause and vehicle. Check the vehicle-specific issues below for estimated costs.

Which vehicles are affected by P0172?

Au7o has documented P0172 across 7 vehicle models from 6 manufacturers: BMW, Ford, GMC, Kia, Subaru, Volvo. See the full list below for vehicle-specific causes and repair costs.

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