DTC P0140 [LF]: Notes

DTC P0140 (LF) DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0140	HO2S no activity detected
DETECTION CONDITION	The PCM monitors the input voltage from the HO2S when the following conditions are met. Under the following monitoring conditions, if the input voltage from the HO2S does not even exceed 0.55 V though the short term fuel trim is controlled up to 20.5% for 9.6 s , the PCM determines that sensor circuit is not activated. MONITORING CONDITIONS PCM Adaptive Memory Production, EGR System, A/F Sensor Heater, HO2S Heater, A/F Sensor, HO2S, and TWC Repair Verification Drive Mode Following conditions are met for above 20.8 s : Engine speed: above 1,500 RPM Engine coolant temperature: above 70°C {158°F} HO2S voltage: above 0.1 V Diagnostic support note This is an intermittent monitor (A/F sensor, 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 (Mode 2/Mode 12) is available. The DTC is stored in the PCM memory.
POSSIBLE CAUSE	HO2S looseness HO2S connector or terminals malfunction HO2S heater malfunction Short to ground in wiring harness between HO2S terminal A and PCM terminal 2Q PCM connector or terminals malfunction Open circuit in wiring harness between HO2S terminal A and PCM terminal 2Q HO2S malfunction Leakage exhaust system HO2S deterioration Engine malfunction Leakage engine coolant to combustion chamber Insufficient compression PCM malfunction
Courtesy of MAZDA MOTORS CORP.

DTC P0140

HO2S no activity detected

DETECTION CONDITION

The PCM monitors the input voltage from the HO2S when the following conditions are met. Under the following monitoring conditions, if the input voltage from the HO2S does not even exceed 0.55 V though the short term fuel trim is controlled up to 20.5% for 9.6 s , the PCM determines that sensor circuit is not activated.
MONITORING CONDITIONS
- PCM Adaptive Memory Production, EGR System, A/F Sensor Heater, HO2S Heater, A/F Sensor, HO2S, and TWC Repair Verification Drive Mode
- Following conditions are met for above 20.8 s :
  - Engine speed: above 1,500 RPM
  - Engine coolant temperature: above 70°C {158°F}
- HO2S voltage: above 0.1 V

Diagnostic support note

This is an intermittent monitor (A/F sensor, 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 (Mode 2/Mode 12) is available.
The DTC is stored in the PCM memory.

POSSIBLE CAUSE

HO2S looseness
HO2S connector or terminals malfunction
HO2S heater malfunction
Short to ground in wiring harness between HO2S terminal A and PCM terminal 2Q
PCM connector or terminals malfunction
Open circuit in wiring harness between HO2S terminal A and PCM terminal 2Q
HO2S malfunction
- Leakage exhaust system
- HO2S deterioration
Engine malfunction
- Leakage engine coolant to combustion chamber
- Insufficient compression
PCM malfunction

Courtesy of MAZDA MOTORS CORP.