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Home >> Hyundai >> 2002 >> Accent GL Hatchback L4-1.6L >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0031

P0031



P0031 - O2 Sensor Heater Circuit Low (bank 1, sensor 2)




Component Location

General Description

In order to control the emission of the CO, HC and NOx components of the exhaust gas, a heated oxygen sensor (HO2S), mounted on the front side and rear side of the catalytic converter, detects the oxygen content in the exhaust gas. The front HO2S signal is used to control air/fuel ratio (closed loop fuel control) and the rear HO2S signal is used to monitor front HO2S and catalyst for proper operation. The HO2S requires a minimum temperature to operate properly and provide a closed loop fuel control system. So the HO2S contains a heater element to reduce warm-up time and ensure proper performance during all driving conditions, which allows for closed loop fuel control or catalyst monitoring immediately upon engine start-up. The ECM controls this heater element by duty cycle. The main relay supplies voltage to the heater and the PCM provides a ground circuit for activating the heater.

DTC Description

The PCM sets P0031 if the PCM detects that the front HO2S heater control line is short to ground.





DTC Detecting Condition




Specification




Schematic Diagram

Signal Waveform




This figure shows the wave form measured at terminal 3 of HO2S.


1. Point (1) is the duration heater operates and the normal voltage is below 0.8V.

A. In case the output voltage is over 0.8V.

>> Possible cause:Poor PCM ground connection Or poor PCM connector�s connection

2. Point (2) is the duration heater doesn't operates and the normal voltage is battery voltage.

Monitor DTC Status

This is the inspection procedure to determine whether it is present DTC or memoried one by monitoring the current signal or by using the function of oscilloscope with Hi-scan pro.

1. Connect scantool to Data Link Connector(DLC).

2. Warm up the engine to normal operating temperature.




3. Monitor the "A/F CLOSE LOOP" parameter on the scantool.

NOTE: The data shown above is only for reference and there may be a little difference actually.

4. Is parameter displayed within specifications?

YES
1) Fault is intermittent caused by poor contact in the sensor�s and/or PCM�s connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination,deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.

NO
1) Go to "W/Harness Inspection" procedure


Terminal and Connector Inspection

1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination,deterioration, or damage.

3. Has a problem been found?

YES
1) Repair as necessary and go to "Verification of vehicle Repair" procedure.

NO
1) Go to "Power Circuit inspection" procedure



Power Supply Circuit Inspection

1. Ignition "OFF"

2. Disconnect HO2S sensor connector.

3. Ignition "ON" & Engine "OFF"




4. Measure voltage between terminal 4 of sensor harness connector and chassis ground.

A. Specification : approximately B+

5. Is measure voltage within Specification?

YES
1) Go to "Control circuit inspection" procedure.

NO
1) Open or short circuit to chassis ground between HO2S harness connector and control relay. Repair as necessary and then go to "Verification of Vehicle Repair" procedure.



NOTE: In case,when checking sensor voltage,the output voltage is 0V.

>Possible cause: Blown fuse or open circuit in harness between E/C-J/BOX and terminal 4 of HO2S heater.


Control Circuit Inspection

1. Ignition "OFF"

2. Disconnect HO2S sensor connector.

3. Ignition "ON" & Engine "OFF"




4. Measure voltage between terminal 3 of sensor harness connector.

A. Specification : approximately 3.7V

5. Is measure voltage within Specification?

YES
1) Go to "Component Inspection" procedure.

NO
1) Check for open or Short to ground in control circuit. Repair as necessary and then go to "Verification of Vehicle Repair" procedure.


Component Inspection

1. Check HO2S heater





(1) Measure resistance between terminal 3 and 4 of sensor connector(To sensor side)

A. Specification : 80�C : 8.0~14.ohms


(2) Is measure resistance within Specification?

YES
1) Substitute with a known good PCM and check for proper operation. If the problem is corrected, replace PCM and then go to "Verification of Vehicle Repair" procedure.

NO
1) Substitute with a known-good HO2S heater and check for proper operation. If the problem is corrected, replace HO2S heater and then go to "Verification of Vehicle Repair" procedure.


Verification Vehicle Repair

After a repair, it may be necessary to check that fault is properly rectified.

1. Review and record the Freeze Frame Data for the Diagnostic Trouble Code (DTC) which has been diagnosed.
2. Using a Scantool, Clear DTC.


Caution

Record all freeze frame data before disconnecting any connectors or clearing code(s). When DTCs are cleared, the Freeze Frame data which may help diagnosed an intermittent fault will also be erased from ECM's memory.

3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.


Caution

Freeze Frame Data: The Freeze Frame function is designed to provide technicians with engine and vehicle information at the time a code is set. Freeze Frame can be thought of as a snapshot of certain operating conditions present at the time the MIL is turned on and a code set. Because this data is critical to determining the cause of a malfunction, this particular data is locked into a Freeze Frame Data memory location. If more than one DTC is encountered, the first one detected will have Freeze Frame Data available.

4. Review Scantool data referring Readiness Test mode and check the test result is complete


Caution

Readiness Test Incomplete message indicates the ECM has not tested a system. If a customer complaint is present at the time of repair, it is important to run (complete) of the readiness tests. If a vehicle has DTC, some readiness tests will not complete since some electrical problems will make it impossible for the ECM to monitor signals during system operation. Run all the OBD monitors to get suitable readiness tests to complete after repair the system.

5. Monitoring for (pending) DTC. Is the same DTC set?

YES
1) Go to the applicable troubleshooting procedure.
NO
1) System OK


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