DTC P0031


DTC P0031	HO2S heater circuit low input
DETECTION CONDITION	• The PCM monitors the HO2S heater control signal at PCM terminal 2AM. If the PCM turns the HO2S heater off but the HO2S heater circuit has low voltage, the PCM determines that the HO2S heater circuit has a malfunction. Note • The HO2S heater is controlled by a duty signal. Diagnostic support note • This is a continuous monitor (Oxygen sensor 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 PCM memory.
POSSIBLE CAUSE	• HO2S malfunction • Open circuit between HO2S terminal C and PCM terminal 2T • Open circuit between HO2S terminal D and PCM terminal 2AM • Short to ground between HO2S terminal D and PCM terminal 2AM • Poor connection at the HO2S or PCM connector • PCM malfunction


STEP	INSPECTION		ACTION
1	PERFORM DTC CONFIRMATION PROCEDURE • Perform the DTC CONFIRMATION PROCEDURE. (See DTC CONFIRMATION PROCEDURE.) • Is the same DTC present?	Yes	Go to the next step.
1		No	Intermittent concern exists. Go to the INTERMITTENT CONCERN TROUBLESHOOTING procedure. (See INTERMITTENT CONCERN TROUBLESHOOTING.)
2	INSPECTH2OS FOR POOR CONNECTION • Turn the ignition switch off. • Disconnect the HO2S 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 8.
2		No	Go to the next step.
3	INSPECT HO2S HEATER • Inspect the HO2S heater. (See HEATED OXYGEN SENSOR (HO2S) INSPECTION.) • Is the HO2S heater normal?	Yes	Go to the next step.
3		No	Replace the HO2S, then go to Step 8.
4	INSPECT POWER CIRCUIT OF HO2S HEATER FOR OPEN CIRCUIT • Turn the ignition switch to the ON position (engine off). • Measure the voltage between HO2S terminal C (wiring harness-side) and body ground. • Is the voltage B+?	Yes	Go to the next step.
4		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 off. • Disconnect the PCM connector. • Inspect for poor connection (such as damaged, pulled-out pins, and corrosion). • Is there any malfunction?	Yes	Repair the terminal, then go to Step 8.
5		No	Go to the next step.
6	INSPECT CONTROL CIRCUIT OF HO2S HEATER FOR SHORT TO GROUND • Inspect continuity between the HO2S terminal D (wiring 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.
6		No	Go to the next step.
7	INSPECT CONTROL CIRCUIT OF HO2S HEATER FOR OPEN CIRCUIT • Remove the PCM with the PCM connector connected. • Inspect continuity between HO2S terminal D (wiring harness-side) and PCM terminal 2AM (wiring harness-side). • Is there continuity?	Yes	Go to the next step.
7		No	Repair or replace the wiring harness for an open circuit, then go to Step 8.
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. (See KOEO/KOER SELF-TEST.) • Is the same DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION.)
8		No	Go to the next step.
9	VERIFY AFTER REPAIR PROCEDURE • Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE.) • Are any DTCs present?	Yes	Go to the applicable DTC troubleshooting. (See DTC TABLE.)
9		No	Troubleshooting completed.