DTC P0031 [LF ATX (FN4A-EL), L3 ATX]

id0102b6802000

DTC P0031

A/F sensor heater 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 or on but the A/F sensor heater circuit remains low voltage, the PCM determines that the A/F sensor heater circuit has a malfunction.
Note
•  The A/F sensor heater is controlled by duty signal.
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 heater malfunction
•  Connector or terminal malfunction
•  Open circuit in wiring harness between main relay and A/F sensor terminal A
•  Short to ground in wiring harness between main relay and A/F sensor terminal A
•  Open circuit in wiring harness between A/F sensor terminal E and PCM terminal 2G
•  Short to ground in wiring harness between A/F sensor terminal E and PCM terminal 2G
•  PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
VERIFY FREEZE FRAME DATA HAVE BEEN RECORDED
•  Have FREEZE FRAME DATA been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA on the repair order, then go to the next step.
2
VERIFY RELATED SERVICE INFORMATION AVAILABILITY
•  Verify related Service Information availability.
•  Is any related Service Information available?
Yes
Perform repair or diagnosis according to the available Service Information.
•  If the vehicle is not repaired, go to the next step.
No
Go to the next step.
3
INSPECT A/F SENSOR CONNECTOR FOR POOR CONNECTION
•  Turn the ignition switch off.
•  Disconnect the A/F sensor connector.
•  Inspect for poor connection (such as damaged/pulled-out pins, and corrosion).
•  Is there any malfunction?
Yes
Repair or replace the terminal, then go to Step 9.
No
Go to the next step.
4
INSPECT A/F SENSOR HEATER POWER CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GROUND
•  Turn the ignition switch to the ON position (Engine off).
•  Measure the voltage between A/F sensor terminal A and body ground.
•  Is the voltage B+?
Yes
Go to the next step.
No
Repair or replace the wiring harness for a possible open circuit or short to ground, then go to Step 9.
5
INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR SHORT TO GROUND
•  Turn the ignition switch off.
•  Inspect for continuity between A/F sensor terminal E and body ground.
•  Is there continuity?
Yes
Repair or replace the wiring harness for a possible short to ground, then go to Step 9.
No
Go to the next step.
6
INSPECT A/F SENSOR HEATER
•  Inspect the A/F sensor heater.
•  Is there any malfunction?
Yes
Replace the A/F sensor, then go to Step 9.
(See AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [LF, L3].)
No
Go to the next step.
7
INSPECT PCM CONNECTOR FOR POOR CONNECTION
•  Turn the ignition switch off.
•  Disconnect the PCM connector.
•  Inspect for poor connection (such as damaged/pulled-out pins, and corrosion).
•  Is there any malfunction?
Yes
Repair or replace the terminal, then go to Step 9.
No
Go to the next step.
8
INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR OPEN CIRCUIT
•  Turn the ignition switch off.
•  Inspect for continuity between A/F sensor terminal E and PCM terminal 2G.
•  Is there continuity?
Yes
Go to the next step.
No
Repair or replace the wiring harness for a possible open circuit, then go to the next step.
9
VERIFY TROUBLESHOOTING OF DTC P0031 COMPLETED
•  Make sure to reconnect all disconnected connectors.
•  Clear the DTC from the PCM memory using the M-MDS.
•  Perform the KOEO or KOER self-test.
•  Is the DTC P0031 present?
Yes
Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION [LF, L3].)
No
Go to the next step.
10
VERIFY AFTER REPAIR PROCEDURE
•  Perform the “AFTER REPAIR PROCEDURE”.
•  Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [LF ATX (FN4A-EL), L3 ATX].)
No
DTC troubleshooting completed.