DTC P0031 [L3]

BME010200001W01

DTC P0031

Front HO2S heater circuit low input

DETECTION CONDITION

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