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.

Checking output signals from HO2S under detecting condition, if HO2S's signal is rich during fuel cut-off conditions, PCM sets P2273. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

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.

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.

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?

▶ 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 HO2S 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 automaticallydetected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others.

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

4.

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

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

▶ Go to the applicable troubleshooting procedure.