DTC P0031 [LF]: Notes

DTC P0031 (LF) DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0031	A/F sensor heater circuit low input
DETECTION CONDITION	The PCM monitors the A/F sensor heater control voltage when the PCM turns the A/F sensor heater on. If the control voltage is less than 50% of the battery voltage, the PCM determines that the A/F sensor heater control circuit voltage is low. Diagnostic support note This is a continuous monitor (A/F sensor heater, HO2S heater). 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	A/F sensor connector or terminals malfunction Open circuit or short to ground in A/F sensor heater power supply circuit Short to ground in wiring harness between ignition relay and A/F sensor terminal C A/F sensor heater power supply circuit related fuse malfunction Open circuit in wiring harness between ignition relay and A/F sensor terminal C A/F sensor heater malfunction Short to ground in wiring harness between A/F sensor terminal D and PCM terminal 2BG PCM connector or terminals malfunction Open circuit in wiring harness between A/F sensor terminal D and PCM terminal 2BG PCM malfunction
Courtesy of MAZDA MOTORS CORP.

DTC P0031

A/F sensor heater circuit low input

DETECTION CONDITION

The PCM monitors the A/F sensor heater control voltage when the PCM turns the A/F sensor heater on. If the control voltage is less than 50% of the battery voltage, the PCM determines that the A/F sensor heater control circuit voltage is low.

Diagnostic support note

This is a continuous monitor (A/F sensor heater, HO2S heater).
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

A/F sensor connector or terminals malfunction
Open circuit or short to ground in A/F sensor heater power supply circuit
- Short to ground in wiring harness between ignition relay and A/F sensor terminal C
- A/F sensor heater power supply circuit related fuse malfunction
- Open circuit in wiring harness between ignition relay and A/F sensor terminal C
A/F sensor heater malfunction
Short to ground in wiring harness between A/F sensor terminal D and PCM terminal 2BG
PCM connector or terminals malfunction
Open circuit in wiring harness between A/F sensor terminal D and PCM terminal 2BG
PCM malfunction

Courtesy of MAZDA MOTORS CORP.