Isuzu 1999 RODEO Workshop Manual page 787

6E1–160 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
f A history Diagnostic Trouble Code P0137 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
f Diagnostic Trouble Code P0137 can be cleared by
using the Scan Tool's "Clear Info" function.
Diagnostic Aids
Check for the following conditions:
f Heated oxygen sensor wiring – The sensor pigtail may
be mispositioned and/or contacting the exhaust
system.
f Poor PCM to engine grounds.
f Fuel pressure – A condition which causes a lean
exhaust can cause Diagnostic Trouble Code P0137 to
set. The system will go lean if pressure is too low. The
PCM can compensate for some decrease. However, if
fuel pressure is too low, a Diagnostic Trouble Code
P0137 may be set. Refer to Fuel System Diagnosis.
f Lean injector(s) – Perform "Injector Balance Test."
f Vacuum leaks – Check for disconnected or damaged
vacuum hoses and for vacuum leaks at the intake
manifold, throttle body, EGR system, and PCV system.
f Exhaust leaks – An exhaust leak may cause outside air
to be pulled into the exhaust gas stream past the
DTC P0137 – O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
Step
1 Was the "On–Board Diagnostic (OBD) System Check"
performed?
2 1. Install the Tech 2.
2. Run the engine at operating temperature.
3. Operate the vehicle within the parameters specified
under "Conditions for Setting the Diagnostic
Trouble Code" criteria included in Diagnostic
Support.
4. Using a Tech 2, monitor Bank 1 HO2S 2 voltage.
Does the Bank 1 HO2S 2 voltage remain below the
specified value?
3 1. Ignition ON, engine OFF review and record Tech 2
Failure Records data and note parameters.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using a Tech 2, monitor "Diagnostic Trouble Code"
info for Diagnostic Trouble Code P0137 until the
Diagnostic Trouble Code P0137 test runs.
4. Note the test result.
Does the Tech 2 indicate Diagnostic Trouble Code
P0137 failed this ignition?
4 1. Turn ignition OFF.
2. Disconnect the PCM.
3. Check the Bank 1 HO2S 2 high and low signal
circuits for a short to ground or a short to the heater
ground circuit.
Were Bank 1 HO2S 2 signal circuits shorted?
5 Repair the Bank 1 HO2S 2 signal circuit.
Is the action complete?
Action
HO2S, causing the Diagnostic Trouble Code P0137 to
set. Check for exhaust leaks near the Bank 1 HO2S 2
sensor.
f Fuel contamination – Water, even in small amounts,
can be delivered to the fuel injectors. The water can
cause a lean exhaust to be indicated. Excessive
alcohol in the fuel can also cause this condition. For
procedure to check for fuel contamination, refer to Fuel
System Diagnosis.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
3. Diagnostic Trouble Code P0137 being set in power
enrichment mode conditions may indicate a
condition described in the "Diagnostic Aids" above.
If the Diagnostic Trouble Code P0137 test passes
while the Failure Records conditions are being
duplicated, an intermittent condition is indicated.
Reviewing the Failure Records vehicle mileage
since the diagnostic test last failed may help
determine how often the condition that caused the
Diagnostic Trouble Code to be set occurs. This may
assist in diagnosing the condition.
Value(s)
— Go to Step 2
26 mV Go to Step 4
— Go to Step 4
— Go to Step 5
— Verify repair
Yes No
Go to OBD
System
Check
Go to Step 3
Refer to
Diagnostic
Aids
Go to Step 6
—