DTC P0031 [LF, L3]

id0102008020a3

DTC P0031

Front HO2S heater circuit low input

DETECTION CONDITION

• The PCM monitors the front HO2S heater control signal at the 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 front HO2S heater circuit has a malfunction.
Note
• The front HO2S heater is controlled by a duty signal.
Diagnostic support note
• This is a continuous monitor (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.
• The PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.
• The FREEZE FRAME DATA is available.
• The DTC is stored in the 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 the PCM terminal 4A
• Short to ground between front HO2S terminal D and the PCM terminal 4A
• Poor connection at the front HO2S or the PCM connector
• PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION

1
PERFORM DTC CONFIRMATION PROCEDURE
• Perform the DTC CONFIRMATION PROCEDURE.
• Is the same DTC present?
Yes
Go to the next step.
No
Intermittent concern exists. Go to the INTERMITTENT CONCERN TROUBLESHOOTING procedure.
2
INSPECT FRONT HO2S FOR POOR CONNECTION
• Turn the ignition switch to the OFF position.
• Disconnect the front HO2S connector.
• Inspect for poor connection (damaged, pulled-out pins, corrosion, etc.).
• Are there any malfunctions?
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 an open circuit CIRCUIT
• Turn the ignition switch to the ON position (Engine off).
• Measure the voltage between front HO2S terminal C (harness-side) and body ground.
• Is the voltage B+?
Yes
Go to the next step.
No
Repair or replace the wiring harness for an open circuit, then go to Step 8.
5
INSPECT PCM FOR POOR CONNECTION
• Turn the ignition switch to the OFF position.
• Disconnect the PCM connector.
• Inspect for poor connection (damaged, pulled-out pins, corrosion, etc.).
• Are any malfunctions?
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 the continuity between front HO2S terminal D (harness-side) and body ground.
• Is there continuity?
Yes
Repair or replace the wiring harness for a short to ground, then go to Step 8.
No
Go to the next step.
7
INSPECT CONTROL CIRCUIT OF FRONT HO2S HEATER for an open circuit CIRCUIT
• Remove the PCM with the PCM connector connected.
• Inspect the continuity between front HO2S terminal D (harness-side) and the PCM terminal 4A.
• Is there continuity?
Yes
Go to the next step.
No
Repair or replace the wiring harness for an 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 the 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 the "After Repair Procedure".
• Are any DTCs present?
Yes
Go to the applicable DTC troubleshooting.
No
Troubleshooting completed.