Mazda 3 - Dtc P2178 [Lf]

Mazda 3 Workshop Manual – Engine + Wiring Diagrams + Diagnostic Trouble Codes
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409
DTC P2178 [LF]
B3E010202100W02
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 or 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 the above malfunctioning condition in two
consecutive drive cycles or in one drive cycle while the DTC for the same malfunction
has been stored in the PCM.
• PENDING CODE is available if PCM detects the above malfunction conditions
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
Diagnostic procedure
STEP
INSPECTION
ACTION
1
VERIFY FREEZE FRAME DATA HAS
BEEN RECORDED
• Has FREEZE FRAME DATA been
recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA on the
repair order, then go to the next step.