DTC P0031 [L3]

BME010201084201

DTC P0031

Front HO2S heater circuit low input

DETECTION CONDITION

• The PCM monitors the front HO2S heater control signal at PCM terminal 4A. If the PCM turns the front HO2S heater off but the front HO2S heater circuit has low voltage, the PCM determines that the front HO2S heater circuit has a malfunction.
Note
• The front HO2S heater is controlled by duty signal.
Diagnostic support note
• This is an intermittent monitor (O2 sensor heater).
• MIL illuminates if PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while DTC for the same malfunction has been stored in PCM.
• PENDING CODE is available if PCM detects above malfunction condition during first drive cycle.
• FREEZE FRAME DATA is available.
• DTC is stored in PCM memory.

POSSIBLE CAUSE

• Front HO2S malfunction
• Open circuit between ignition switch and front HO2S terminal C
• Open circuit between front HO2S terminal D and PCM terminal 4A
• Short to ground circuit between front HO2S terminal D and PCM terminal 4A
• Poor connection at front HO2S or PCM connector
• PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION

1
PERFORM DTC CONFIRMATION PROCEDURE
• Perform DTC CONFIRMATION PROCEDURE.
• Is the same DTC present?
Yes
Go to the next step.
No
Intermittent concern exists. Go to INTERMITTENT CONCERN TROUBLESHOOTING procedure.
2
INSPECT POOR CONNECTION OF FRONT HO2S CONNECTOR
• Turn the ignition switch off.
• Disconnect the front HO2S connector.
• Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
• Is there any malfunction?
Yes
Repair or replace the terminal, then go to Step 8.
No
Go to the next step.
3
INSPECT FRONT HO2S HEATER
• Inspect the front HO2S heater.
• Is the front HO2S heater normal?
Yes
Go to the next step.
No
Replace the front HO2S, then go to Step 8.
4
INSPECT POWER CIRCUIT OF FRONT HO2S HEATER FOR OPEN CIRCUIT
• Turn the ignition switch to the ON position (Engine off).
• Measure the voltage between front HO2S terminal C (wiring harness-side) and body ground.
• Is the voltage B+?
Yes
Go to the next step.
No
Repair or replace the wiring harness for open circuit, then go to Step 8.
5
INSPECT POOR CONNECTION OF PCM CONNECTOR
• Turn the ignition switch off.
• Disconnect the PCM connector.
• Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
• Is there any malfunction?
Yes
Repair the terminal, then go to Step 8.
No
Go to the next step.
6
INSPECT CONTROL CIRCUIT OF FRONT HO2S HEATER FOR SHORT TO GROUND
• Inspect for continuity between front HO2S terminal D (wiring harness-side) and body ground.
• Is there continuity?
Yes
Repair or replace the wiring harness for short to ground, then go to Step 8.
No
Go to the next step.
7
INSPECT CONTROL CIRCUIT OF FRONT HO2S HEATER FOR OPEN CIRCUIT
• Inspect for continuity between front HO2S terminal D (wiring harness-side) and PCM terminal 4A.
• Is there continuity?
Yes
Go to the next step.
No
Repair or replace the wiring harness for open circuit, then go to the next step.
8
VERIFY TROUBLESHOOTING OF DTC P0031 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Perform KOEO/KOER self-test.
• Is the same DTC present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
9
VERIFY AFTER REPAIR PROCEDURE
• Perform "After Repair Procedure".
• Is there any DTC present?
Yes
Go to the applicable DTC inspection.
No
Troubleshooting completed.