Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

SYS.OK|MANUAL.DB● LIVE

HOMESERVICE MANUALSMAZDA20086 S SPORT, 4D HATCHBACK, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 688 (ON-BOARD DIAGNOSTIC (ENGINE CONTROL SYSTEM L3) (3 OF 5))DTC P0172NOTES

2008 Mazda 6 s Sport, 4D Hatchback, Standard

DTC P0172: Notes

2008 Mazda 6 s Sport, 4D Hatchback, StandardSECTION Notes

WARNING: This page is about a different car, the 2007 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0172 DETECTION CONDITION AND POSSIBLE CAUSES

DTC P0172

Fuel trim system too rich

DETECTION CONDITION

PCM monitors short fuel trim (SHRTFT) and long fuel trim (LONGFT) values when closed loop fuel control. If the LONGFT and the sum total of these fuel trims exceed preprogrammed criteria, PCM determines that the fuel system is too rich.

Diagnostic support note

This is a continuous monitor. (Fuel system)
MIL illuminates if PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while DTC for the same malfunction has been stored in PCM.
PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
FREEZE FRAME DATA is available.
DTC is stored in the PCM memory.

POSSIBLE CAUSE

Misfire
Front HO2S deterioration
Front HO2S heater malfunction
MAF sensor malfunction
EGR valve improper operation
Variable tumble solenoid valve improper operation
Purge solenoid valve improper operation
Pressure regulator malfunction
Fuel pump malfunction
Fuel return hose clogged
Purge solenoid valve malfunction
Purge solenoid hoses improper connection
PCV valve malfunction
PCM malfunction

RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready Tools Free Quote Check Quote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.