Dtc P0138 [Lf] - Mazda 3 Workshop Manual

Mazda 3 Workshop Manual – Engine + Wiring Diagrams + Diagnostic Trouble Codes
DTC P0138
DETECTION
CONDITION
POSSIBLE CAUSE
Diagnostic procedure
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DTC P0138 [LF]

Rear HO2S circuit high input
• 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).
• 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 first drive cycle.
• FREEZE FRAME DATA is available.
• DTC is stored in the PCM memory.
• Rear HO2S malfunction
• Short to power supply in wiring harness between rear HO2S terminal A and
PCM terminal 2AH
• Rear HO2S or PCM terminal shorted
• PCM malfunction
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