SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSMAZDA20066 I, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMON-BOARD DIAGNOSTIC [ENGINE CONTROL SYSTEM L3)DTC P2178NOTES
2006 Mazda 6 i, 4D Sedan, Automatic

DTC P2178: Notes

2006 Mazda 6 i, 4D Sedan, AutomaticSECTION Notes
DTC P2178 DETECTION CONDITION AND POSSIBLE CAUSES

DTC P2178 Fuel system too rich at off idle
DETECTION CONDITION 
  • PCM monitors short term fuel trim (SHRTFT), long term fuel trim (LONGFT) during closed loop fuel control at off-idle. If the LONGFT and the sum total of these fuel trims exceed preprogrammed criteria. PCM determines that fuel system is too rich at off-idle.

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
  • Pressure regulator (built-in fuel injection pump) malfunction
  • Fuel pump malfunction
  • EGR valve improper operation
  • VTCS improper operation
  • Purge solenoid valve improper operation
  • Purge solenoid valve malfunction (stuck open)
  • Purge solenoid hoses improper connection
  • PCV valve malfunction
  • Variable valve timing control system improper operation
  • 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 ToolsFree Quote CheckQuote 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.