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 an output signal is below 0.04V
for more than predetermined time, PCM sets P0137. MIL(Malfunction
Indication Lamp) turns on when the malfunction lasts till consecutive 2
driving cycle.
Item
|
Detecting
Condition
|
Possible cause
|
DTC
Strategy
|
|
| •
|
Short to ground in
harness |
|
Enable
Conditions
|
| •
|
Engine running ≥ 60
sec. |
|
Threshold
value
|
| •
|
The voltage of HO2S(B1/S2) <
0.04V | |
Diagnosis
Time
|
| •
|
Continuous
(more than 12.5 sec. failure for every
15 sec.test) | |
MIL On
Condition
|
|
(Reference only)
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
|
The amplitude of the
signal output of the rear HO2S is small compared to the front HO2S because
the rear HO2S detects emission gas purified by the catalytic converter.
This is the normal signal waveform of the rear HO2S at idle.
| 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 "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 terminal condition. 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 |
■ Check Short To Ground In Harness
| 1. |
IG "OFF" and disconnect
HO2S(B1/S2) |
| 3. |
Measure voltage between signal terminal 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 ground in harness, and go to "Verification of Vehicle
Repair"
procedure.
|
|
| 1. |
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 HO2S" as indicated 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.
|
|
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 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.
|
|
