DTC P0031:00 [L5]: Notes

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DETECTION CONDITIONS & POSSIBLE CAUSES

DTC P0031:00	A/F sensor heater control circuit low input
DETECTION CONDITION	The PCM monitors the A/F sensor heater output voltage. If the PCM turns the A/F sensor heater off but the A/F sensor heater circuit remains low voltage, the PCM determines that the A/F sensor heater circuit has a malfunction. 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 is available The DTC is stored in the PCM memory.
POSSIBLE CAUSE	A/F sensor connector or terminal malfunction Short to ground in wiring harness between main relay terminal D and A/F sensor terminal A Open circuit in wiring harness between main relay terminal D and A/F sensor terminal A PCM connector or terminal malfunction Short to ground in wiring harness between A/F sensor terminal E and PCM terminal 2A A/F sensor heater malfunction Open circuit in wiring harness between A/F sensor terminal E and PCM terminal 2A PCM malfunction
Courtesy of MAZDA MOTORS CORP.

DTC P0031:00

A/F sensor heater control circuit low input

DETECTION CONDITION

The PCM monitors the A/F sensor heater output voltage. If the PCM turns the A/F sensor heater off but the A/F sensor heater circuit remains low voltage, the PCM determines that the A/F sensor heater circuit has a malfunction.

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 is available
The DTC is stored in the PCM memory.

POSSIBLE CAUSE

A/F sensor connector or terminal malfunction
Short to ground in wiring harness between main relay terminal D and A/F sensor terminal A
Open circuit in wiring harness between main relay terminal D and A/F sensor terminal A
PCM connector or terminal malfunction
Short to ground in wiring harness between A/F sensor terminal E and PCM terminal 2A
A/F sensor heater malfunction
Open circuit in wiring harness between A/F sensor terminal E and PCM terminal 2A
PCM malfunction

Courtesy of MAZDA MOTORS CORP.