Isuzu 1999 RODEO Workshop Manual page 772

Trouble Code P0131 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
HO2S, causing the system to appear lean. Check for
exhaust leaks that may cause a false lean condition to
be indicated.
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 the
procedure to check for fuel contamination, Refer to
Fuel System Diagnosis.
If none of the above conditions are present, replace the
affected HO2S.
DTC P0131 – O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
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 1 voltage.
Does the Bank 1 HO2S 1 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 P0131 until the
Diagnostic Trouble Code P0131 test runs.
Note test result.
Does Tech 2 indicate DTC P0131 failed this ignition?
4 1. Turn the ignition OFF.
2. Disconnect the PCM.
3. Check the Bank 1 HO2S 1 high and low circuits for a
short to ground or a short to the heater ground
circuit.
Are the Bank 1 HO2S 1 signal circuits shorted to
ground?
5 Repair the Bank 1 HO2S 1 signal circuit.
Is the action complete?
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
Action
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
3. Diagnostic Trouble Code P0131 failing during
operation may indicate a condition described in the
"Diagnostic Aids" above. If the Diagnostic Trouble
Code P0131 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
300 mV Go to Step 4
— Go to Step 4
— Go to Step 5
— Verify repair
6E1–145
Yes No
Go to OBD
System
Check
Go to Step 3
Refer to
Diagnostic
Aids
Go to Step 6
—