In order to provide the
best possible combination of drivability, fuel economy and emission
control, the ECM uses a closed loop air/fuel metering system. The ECM
monitors the HO2S signal voltage and adjusts fuel delivery based it in
closed loop fuel control. Changes in fuel delivery will be indicated by
the long-term and the short-term fuel trim values. The ideal fuel trim
value is around 0%. The ECM will add fuel when the HO2S signal is
indicating a lean condition. Additional fuel is indicated by fuel trim
values that are above 0%. The ECM will reduce fuel when the HO2S signal is
indicating a rich condition. Reduction in fuel is indicated by fuel trim
values that are below 0%. The DTC relevant to fuel trim will be set when
the amount reaches excessive levels because of a lean or rich
condition.
If the lambda controller
reaches the maximum or minimum threshold, then feedback control is no
longer possible and emissions will be increased. The ECM sets DTC P2098 if
no proportional post catalyst fuel trim adaptation occurs for a defined
time after the lambda controller has reached its maximum
threshold.
Item
|
Detecting
Condition
|
Possible cause
|
DTC
Strategy
|
| •
|
Fuel Trim Rear Sensor Control Limits
Exceeded | |
| •
|
Air leakage in exhaust
System |
|
Enable
Conditions
|
| •
|
Barometric Pressure ≥ 74
kPa |
| •
|
Intake Air Temperature ≥ -10
°C |
| •
|
System Voltage ≥ 10.9936
V |
| •
|
Disabling Fault not
present | |
Threshold
value
|
| •
|
Front O2 Sensor switch point ≥
0.6V
Rear O2 Sensor Voltage <
0.25V | |
Diagnosis
Time
|
| •
|
Fail count > 60 within 80 samples
250ms continuous loop | |
MIL On
Condition
|
|
|
If any codes relating to Rear HO2S or
TWC(ThreeWay Catalyst Converter) are stored, do ALL REPAIRS
associated with those codes before proceeding with this
troubleshooting tree. |
| 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 "History(Not
Present) fault"?
| - |
History (Not Present) fault
: DTC occurred but has been
cleared. |
| - |
Present fault : DTC is
occurring at present
time. | |
|
|
▶
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, poorconnection, ending, corrosion,
contamination, deterioration, or damage. Repair or
replace asnecessary and go to "Verification of Vehicle
Repair" procedure.
|
|
|
▶ Go
to "Component Inspection"
procedure.
|
| |
| 1. |
Check Exhaust system
| (1) |
Visually/physically inspect the
following conditions:
| A. |
Exhaust system between HO2S and
Three way catalyst for air leakage, restriction and
damage. |
| B. |
Damage, and for loose or missing
hardware | |
| (2) |
Was a problem found in any of the above
areas?
|
|
▶
Repair or replace as necessary and go to "Verification
of Vehicle Repair" procedure
|
|
|
▶ Go
to next step as
below
|
| |
| 2. |
Check TWC
| (1) |
Visually/physically inspect the
three-way catalyst(TWC) converter for the following
damage:
| A. |
Severe discoloration caused by
excessive temperature |
| C. |
Internal rattle caused by a
damaged
catalyst | |
| (2) |
Also, ensure that the TWC is a proper
original equipment manufacturer
part. |
| (3) |
Was a problem found?
|
|
▶
Replace TWC and go to "Verification of Vehicle Repair"
procedure
|
|
|
▶ Go
to next step as
below
|
| |
| 3. |
Check HO2S
| (1) |
Visually/physically inspect the HO2S for
the following conditions:
| A. |
Ensure that the HO2S is securely
installed.(Pigtail and wiring harness not making contact
with the exhaust pipe) |
| B. |
Check for corrosion on terminals
and terminal tension (at the HO2S and at the
ECM) |
| C. |
Front HO2S for silicon
contamination. This contamination will be indicated by a
white powderycoating on the portion of the sensor
exposed to the exhaust stream and this will result in a
butfalse(high) voltage
signal |
| D. |
Fuel, engine coolant or oil
contamination |
| E. |
Use of improper
sealant |
| F. |
If contamination is evident on the
HO2S, Fix the source of the sensor contamination before
replacingthe sensor to prevent future contamination. Go
to "Verification of Vehicle Repair"
procedure. | |
| (2) |
Warm up the engine to normal operating
temperature and let it idle. |
| (3) |
Connect Scantool and monitor the "O2
SNSR VOL.-B2/S1" and "O2 SNSR VOL.-B2/S2"parameters on the
Scantool data list.
Specification :
- Front HO2S(O2 SNSR VOL.-B2/S1) :
Approx. 0~1V with idle after warm upSensor voltage
increase during engine acceleration and decrease during
enginedeceleration
Approx. 0V ~ 0.4 V when fuel
cut
- Rear HO2S(O2 SNSR VOL.-B2/S2) :
Above 0.4V at idle
| |
| (4) |
Was a problem found in any of the above
areas?
|
|
▶
Repair or replace as necessary and go to "Verification
of Vehicle Repair" procedure
|
|
|
▶
Check for poor connection between ECM and component:
backed out terminal, improper mating,broken locks or
poor terminal to wire connection. Repair as necessary
and go to "Verification ofVehicle Repair"
procedure
|
| |
| Verification Of Vehicle
Repair |
| 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.
|
|
