2006 Mazda MX-5 Miata BaseFACTORY OEM SERVICE PROCEDURE

DTC P0133: Notes

DETECTION CONDITION AND POSSIBLE CAUSE (DTC P0133)

DTC P0133 Front HO2S circuit problem
DETECTION CONDITION 
  • Front HO2S malfunction is detected by measuring of the average frequency of front HO2S signal, time required to pass from rich to lean, time required to pass from lean to rich. If the average frequency of front HO2S signal is more than the threshold value, the PCM determines that there is the front HO2S circuit problem.
MONITORING CONDITIONS 
  • HO2S heater, HO2S, and TWC Repair Verification Drive Mode
  • Following conditions are met:
  • Engine speed is 1,750-3,500 rpm  .
  • Charging efficiency is 25-63%  (at engine speed 2,500 rpm  ).
  • Engine coolant temperature is above 70°C {158°F} 
  • Front HO2S heater monitor is completed.
  • Fuel system loop status is closed loop fuel control.
Diagnostic support note 
  • This is an intermittent monitor. (HO2S)
  • The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
  • DIAGNOSTIC MONITORING TEST RESULTS is available.
  • PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.
  • FREEZE FRAME DATA is available.
  • The DTC is stored in the PCM memory.
POSSIBLE CAUSE 
  • Front HO2S deterioration
  • Front HO2S malfunction
  • Front HO2S looseness
  • Pressure regulator (built-in fuel pump unit) malfunction
  • Fuel pump malfunction
  • Clogged or restricted fuel filter (built-in fuel pump unit)
  • Fuel leakage in fuel line between fuel distribution pipe and fuel pump
  • Exhaust system leakage
  • Purge solenoid valve malfunction
  • Improper connection purge solenoid hose
  • Insufficient compression
  • Engine malfunction (Engine coolant leakage)
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  • • You smell fuel, burning insulation, or see smoke.
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  • • 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.

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