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DTC P0031 [L8, LF, L3]

id0102a1802000

DTC P0031 | A/F sensor heater circuit low input
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DETECTION CONDITION | • The PCM monitors the A/F sensor heater output voltage. if the PCM turns the A/F sensor heater off or on but the A/F sensor heater circuit remains low voltage, the PCM determines that the A/F sensor heater circuit has a malfunction. Note • The A/F sensor heater is controlled by duty signal. Diagnostic support note • This is an intermittent 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 is available. • The DTC is stored in the PCM memory.
POSSIBLE CAUSE | • A/F sensor heater malfunction • Connector or terminal malfunction • Open circuit in wiring harness between main relay and A/F sensor terminal 2B • Short to ground in wiring harness between main relay and A/F sensor terminal 2B • Open circuit in wiring harness between A/F sensor terminal 2D and PCM terminal 2BG • Short to ground in wiring harness between A/F sensor terminal 2D and PCM terminal 2BG • PCM malfunction

Diagnostic procedure

STEP | INSPECTION | ACTION
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1 | VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded? | Yes | Go to the next step.
No | Record the FREEZE FRAME on the repair order, then go to the next step.
2 | VERIFY RELATED REPAIR INFORMATION AVAILABILITY • Verify related Service Information availability. • Is any related Service Information available? | Yes | Perform repair or diagnosis according to the available Service 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 terminal, then go to Step 9.
No | Go to the next step.
4 | INSPECT A/F SENSOR HEATER POWER CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GROUND • Turn the ignition switch to the ON position (Engine off). • Measure the voltage between A/F sensor terminal 2B (wiring harness-side) and body ground. • Is the voltage B+? | Yes | Go to the next step.
No | Repair or replace the wiring harness for a possible open circuit or short to ground, then go to Step 9.
5 | INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR SHORT TO GROUND • Turn the ignition switch off. • Inspect for continuity between A/F sensor terminal 2D (wiring harness-side) and body ground. • Is there continuity? | Yes | Repair or replace the wiring harness for a possible short to ground, then go to Step 9.
No | Go to the next step.
6 | INSPECT A/F SENSOR HEATER • Inspect the A/F sensor heater. (See AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) INSPECTION [L8, LF, L3].) • Is there any malfunction? | Yes | Replace the A/F sensor, then go to Step 9. (See EXHAUST SYSTEM REMOVAL/INSTALLATION [L8, LF, L3 2WD].) (See EXHAUST SYSTEM REMOVAL/INSTALLATION [L3 4WD].)
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 terminal, then go to Step 9.
No | Go to the next step.
8 | INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR OPEN CIRCUIT • Turn the ignition switch off. • Inspect for continuity between A/F sensor terminal 2D (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 WDS or equivalent. • Perform the KOEO or KOER self-test. (See KOEO/KOER SELF TEST [L8, LF, L3].) • Is the DTC P0031 present? | Yes | Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [L8, LF, L3].)
No | Go to the next step.
10 | VERIFY AFTER REPAIR PROCEDURE • Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE [L8, LF, L3].) • Are any DTCs present? | Yes | Go to the applicable DTC inspection. (See DTC TABLE [L8, LF, L3].)
No | DTC troubleshooting completed.