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 an output signal is above 1.3V for more than predeterminate time, PCM sets P0138. 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 signal voltage
●
Poor connection
●
Short to battery in harness
●
HO2S(B1/S2)
●
PCM
Enable Conditions
●
Battery voltage ≥ 10V
●
Engine running ≥ 60 sec
●
Engine warm-up state
Threshold value
●
The voltage of HO2S(B1/S2) ＞ 1.3V
Diagnosis Time
●
Continuous
(more than 12.5 sec.failure for every 15 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 "Terminal and connector 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.
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?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to " Signal Circuit Inspection " procedure.
SIGNAL CIRCUIT INSPECTION
1.
IG "OFF" and disconnect HO2S(B1/S2) connector.
2.
IG "ON" and ENG "OFF"
3.
Measure voltage between terminal 1 of HO2S(B1/S2) harness connector and chassis ground.
Specification : Approx. 3.5V - when pumping current is ON
Approx. 0.45V - when pumping current is OFF
4.
Is the measured voltage within specification?
▶ Go to "Component Inspection" procedure.
▶ Repair short to battery in harness, and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1.
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 HO2S" as below.
▶ Substitute with a known - good HO2S and check for proper operation.
If the problem is corrected, go to "Verification of Vehicle Repair" procedure.
2.
Check HO2S
(1)
IG "OFF" and disconnect HO2S connector.
(2)
Check that the HO2S is securely installed.
(3)
Check the HO2S for contamination or damage
(4)
Is the sensor normal?
▶ Substitute with a known - good PCM and check for proper operation.
If the problem is corrected, 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 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.
