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 lean during power
enrichment conditions, PCM sets P2272. MIL(Malfunction Indication Lamp)
turns on when the malfunction lasts till consecutive 2 driving
cycles.
Item
|
Detecting
Condition
|
Possible cause
|
DTC
Strategy
|
|
| •
|
Clogging of fuel filter in fuel
pump |
|
EnableConditions
|
| •
|
Engine running ≥
60sec. |
| •
|
Power Enrichment
conditions |
| •
|
Not in Transient
Conditions | |
Threshold
value
|
| •
|
HO2S's signal < 0.35V and Air Fuel
Ratio ≤ 13.5 | |
DiagnosisTime
|
| •
|
Continuous
(More than 8 sec. failure for every 9
sec. Test) | |
MIL On
Condition
|
|
Test Condition
|
HO2S
Voltage(Sensor1)
|
HO2S
Voltage(Sensor2)
|
HO2S
Signal at idle after warm-up
|
Signal is
normally switching from rich to lean more than 3 times in 10
sec.
|
Signal is
normally 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
|
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. At higher engine RPM, the
switching frequency increases.
| 1. |
Check DTC Status
| (1) |
Connect scantool to Data Link
Connector(DLC). |
| (3) |
Select "DTC" button, and then Press "DTC
Status" 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) |
Are 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. |
| (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
| (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.
|
|
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
before reusing the
PCM | | |
| Verification Of Vehicle
Repair |
After a repair, it is
essential to verify that the fault has been corrected.
| 1. |
Connect scantool and select "DTC"
button. |
| 2. |
Press "DTC Status" button and confirm that
"DTC Readiness Flag" indicates "Completed". 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.
|
|
