COMPONENT LOCATION
GENERAL DESCRIPTION

The rear heated oxygen sensor is mounted on the rear side of the Catalytic Converter (warm-up catalytic converter) or in the rear exhaust pipe, which is able to detect catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0V and 1V. This rear heated oxygen sensor is used to estimate the oxygen storage capability. If a catalyst has good conversion properties, the oxygen fluctuations are smoothed by the oxygen storage capacity of the catalyst. If the conversion provided by the catalyst is low due to aging, poisoning or misfiring, then the oxygen fluctuations are similar to signals from the front oxygen sensor.

DTC DESCRIPTION

Checking output signals from HO2S under detecting condition, if HO2S's signal is lean during power enrichment conditions, PCM sets P2270. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible cause

DTC Strategy

●

Monitor HO2S's signal

●

Poor Connection

●

Faulty HO2S

●

Clogging of fuel filter in fuel pump

●

Faulty PCM

Enable Conditions

●

Battery voltage ≥ 10V

●

Engine running ≥ 60sec.

●

Power Enrichment conditions

●

Engine warm-up state

●

Not in Transient Conditions

Threshold value

●

HO2S's signal ＜ 0.35V and Air Fuel Ratio ≤ 13.5

Diagnosis Time

●

Continuous

(More than 8 sec. failure for every 9 sec. Test)

MIL On Condition

●

2 Driving Cycles

SIGNAL WAVEFORM AND DATA

After warming-up, if accelerator pedal is released suddenly around 4000rpm, the HO2S signal reading will be lower than 200mV resulting from Fuel cut-off for the moment. Conversely, if suddenly accelerator pedal is depressed, HO2S signal reading will be around 0.6V ~1.0V. At idle, Normally HO2S signal will switch from lean to rich with 3 Hz. And as racing, Its frequency rises.

SPECIFICATION
(Reference only)

Test Condition

HO2S Voltage(Sensor1)

HO2S Voltage(Sensor2)

HO2S Signal

at idle after warm-up

Signal is commonly switching from rich to lean more than 3 times in 10 sec.

Signal is commonly above 0.6V.

HO2S signal at open circuit

(Pumping current OFF)

Approx. 0.45V

HO2S signal at open circuit

(Pumping current ON)

Approx. 3.5V

SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1.

Check DTC Status

(1)

Connect scantool to Data Link Connector(DLC).

(2)

IG "ON".

(3)

Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu

(4)

Read "DTC Status" parameter.

(5)

Is parameter displayed "Present fault"?

▶ Go to "Component Inspection" procedure.

▶ 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, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

COMPONENT INSPECTION
1.

Check the condition of HO2S

(1)

Check HO2S for poor connection or loose terminal.

(2)

Check if HO2S is ensurely installed.

(3)

Is the conditions of HO2S normal ?

▶ Go to "Check the Signal waveform of HO2S" as follows.

▶ Repair it and then go to "Verification of Vehicle Repair" procedure.

2.

Check the Signal waveform of HO2S

(1)

IG "OFF" and connect HO2S connector.

(2)

Engine start.

(3)

After warming-up, monitor signal waveform of HO2S with scantool.?

(4)

Is the sensor switching properly?

▶ Go to "Check fuel filter" as follows.

▶ Substitute with a known - good HO2S and check for proper operation.

If the problem is corrected, go to "Verification of Vehicle Repair" procedure.

3.

Check the fuel filter of fuel pump

(1)

IG "OFF" and disconnect the fuel pump connector.

(2)

Start the engine and wait until fuel in fuel line is exhausted. After the engine stalls, IG "OFF"

(3)

Remove the fuel pump assembly.

(4)

Check the fuel filter for clogging by dust, a foreign substance.

(5)

Is the fuel filter O.K.?

▶ Substitute with a known - good PCM and check for proper operation.

If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.

▶ Substitute with a known - good fuel filter and check for proper operation.

If the problem is corrected, go to "Verification of Vehicle Repair" procedure.

note

There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others.

VERIFICATION OF VEHICLE REPAIR

After a repair, it is essential to verify that the fault has been corrected.

1.

Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode

2.

Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions

3.

Read "DTC Status" parameter

4.

Is parameter displayed "History(Not Present) fault"?

▶ System performing to specification at this time. Clear the DTC.

▶ Go to the applicable troubleshooting procedure.

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