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DTC P0031

DTC P0031 A/F sensor heater control circuit low input
DETECTION CONDITION 
  • The input voltage to the A/F sensor heater drive terminal in the PCM is at the set value or less for 1 s or more  even though the A/F sensor heater is duty-controlled at under 90%  by the PCM.

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
  • Short to ground or open circuit in A/F sensor heater power supply circuit
    • Short to ground in wiring harness between main relay terminal C and A/F sensor terminal C
    • A/F sensor heater related fuse malfunction
    • Open circuit in wiring harness between main relay terminal C 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
G07878092
DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 VERIFY FREEZE FRAME DATA (MODE 12) AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED 
  • Have the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS (A/F sensor heater, HO2S heater related) been recorded?
 Yes Go to the next step.
No Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2 VERIFY RELATED REPAIR INFORMATION AVAILABILITY 
  • Verify related Service Bulletins and/or on-line repair information availability.
  • Is any related repair information available?
 Yes Perform repair or diagnosis according to the available repair 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 connector and/or terminals, then go to Step 9.
No Go to the next step.
4 INSPECT A/F SENSOR HEATER POWER SUPPLY CIRCUIT FOR SHORT TO GROUND OR OPEN CIRCUIT 
  • A/F sensor connector is disconnected.
  • Turn the ignition switch to the ON position (engine off).
  • Measure the voltage between A/F sensor terminal C (wiring harness-side) and body ground.
  • Is the voltage B+? 
 Yes Go to the next step.
No Inspect the A/F sensor heater related fuse.
  • If the fuse is melt:
    • Repair or replace the wiring harness for a possible short to ground.
    • Replace the fuse.
  • If the fuse is deterioration:
    • Replace the fuse.
  • If the fuse is normal:
    • Repair or replace the wiring harness for a possible open circuit.

Go to Step 9.
5 INSPECT A/F SENSOR HEATER 
 Yes Replace the A/F sensor, then go to Step 9.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION ).
No Go to the next step.
6 INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR SHORT TO GROUND 
  • A/F sensor connector is disconnected.
  • Turn the ignition switch off.
  • Inspect for continuity between A/F sensor terminal D (wiring harness-side) and body ground.
  • Is there continuity?
 Yes If the short to ground circuit could be detected:
  • Repair or replace the wiring harness for a possible short to ground.

If the short to ground circuit could not be detected:
Go to Step 9.
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 connector and/or terminals, then go to Step 9.
No Go to the next step.
8 INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR OPEN CIRCUIT 
  • A/F sensor and PCM connectors are disconnected.
  • Turn the ignition switch off.
  • Inspect for continuity between A/F sensor terminal D (wiring harness-side) and PCM terminal 2BG (wiring harness-side).
  • 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.

    (See AFTER REPAIR PROCEDURE ).

  • Perform the KOEO or KOER self test.

    (See KOEO/KOER SELF TEST ).

  • Is the PENDING CODE same as the DTC present?
 Yes Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION ).
No Go to the next step.
10 VERIFY AFTER REPAIR PROCEDURE 
 Yes Go to the applicable DTC inspection.
(See DTC TABLE ).
No DTC troubleshooting completed.
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