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Home >> Mazda >> 2006 >> MX-5 Miata Base >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System] >> DTC P0138 >> Notes
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DTC P0138: Notes

DETECTION CONDITION AND POSSIBLE CAUSE (DTC P0138)

DTC P0138 Rear HO2S circuit high input
DETECTION CONDITION 
  • The PCM monitors input voltage from rear HO2S. If the input voltage from the rear HO2S sensor is above 1.2 V  for 0.8 s  , the PCM determines that circuit input is high.
Diagnostic support note 
  • This is a continuous 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.
  • 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 
  • Rear HO2S malfunction
  • Short to power supply in wiring harness between rear HO2S terminal A and PCM terminal 2Q
  • Rear HO2S or PCM terminal shorted
  • PCM malfunction
G04317712Courtesy of MAZDA MOTORS CORP.