DTC P0138: Notes

DTC P0138 (LF, L3) DETECTION CONDITION AND POSSIBLE CAUSES

DTC P0138

Middle⁽¹⁾/Rear⁽²⁾⁽³⁾ HO2S circuit high input

DETECTION CONDITION

The PCM monitors input voltage from middle⁽¹⁾ rear⁽²⁾⁽³⁾ HO2S. If the input voltage from the middle⁽¹⁾/ rear⁽²⁾⁽³⁾ HO2S sensor is above 1.2 V for 0.5 s ⁽¹⁾ /0.8 s ⁽²⁾ ⁽³⁾ , the PCM determines that circuit input is high.

Diagnostic support note

This is a continues 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 first drive cycle.
FREEZE FRAME DATA is available.
DTC is stored in the PCM memory.

POSSIBLE CAUSE

Middle⁽¹⁾/Rear⁽²⁾⁽³⁾ HO2S malfunction
Short to power supply in wiring harness between middle⁽¹⁾/rear⁽²⁾⁽³⁾ HO2S terminal A and PCM terminal 2R⁽¹⁾, 2AH⁽²⁾, 2Q⁽³⁾
Middle⁽¹⁾/Rear⁽²⁾⁽³⁾ HO2S or PCM terminal shorted
PCM malfunction

G04954293

Courtesy of MAZDA MOTORS CORP.

⁽¹⁾	California emission regulation applicable model

⁽²⁾	Except for California emission regulation applicable model with LF ATX

⁽³⁾	Except for California emission regulation applicable model with LF MTX, L3