Isuzu 1999 RODEO Workshop Manual page 784

f A history Diagnostic Trouble Code P0135 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
f Diagnostic Trouble Code P0135 can be cleared by
using the Scan Tool's "Clear Info" function.
Diagnostic Aids
Check for the following conditions:
f Poor connection at PCM – Inspect harness connectors
for backed–out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal–to–wire connection.
f Damaged harness – Inspect the wiring harness for
damage; shorts to ground, shorts to battery positive
and open circuits. If the harness appears to be OK,
observe the ECT display on the Tech 2 while moving
connectors and wiring harnesses related to the sensor.
A change in the display will indicate the location of the
fault.
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.
DTC P0135 – O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
Step
1 Was the "On–Board Diagnostic (OBD) System Check"
performed?
2 NOTE: If the engine has just been operating, allow
engine to cool for about one half hour before
proceeding.
1. Ignition OFF, engine OFF.
2. Install a Tech 2.
3. Ignition ON engine OFF monitor the Bank 1 HO2S 1
voltage.
Does the HO2S voltage go from bias voltage to above
and below the specified values?
3 Inspect the fuse for the Bank 1 HO2S 1 ignition feed.
Is the fuse open?
4 1. Ignition OFF.
2. Raise the vehicle.
3. Disconnect the Bank 1 HO2S 1 electrical connector.
4. Using a test light connected to a good ground (do
not use Bank 1 HO2S 1 heater ground or Bank 1
HO2S 1 low), probe the ignition feed circuit at the
Bank 1 HO2S 1 electrical connector (PCM harness
side).
Does the test light illuminate?
5 Connect the test light between the Bank 1 HO2S 1
ignition feed and the Bank 1 HO2S 1 heater ground.
Does the test light illuminate?
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
Action
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
2. The HO2S should be allowed to cool before
performing this test. If the HO2S heater is
functioning, the signal voltage will gradually increase
or decrease as the sensor element warms. If the
heater is not functioning, the HO2S signal will
remain near the 450 mV bias voltage.
4. Ensures that the ignition feed circuit to the HO2S is
not open or shorted. The test light should be
connected to a good chassis ground, in case the
HO2S low or HO2s heater ground circuit is faulty.
5. Checks the HO2S heater ground circuit.
6. Checks for an open or shorted HO2S heater
element.
10.An open HO2S signal or low circuit can cause the
HO2S heater to appear faulty. Check these circuits
before replacing the sensor.
Value(s)
— Go to Step 2
Above 650
mV or below
Diagnostic
250 mV
Go to Step 15
—
— Go to Step 5
— Go to Step 6
6E1–157
Yes No
Go to OBD
System
Check
Refer to
Aids Go to Step 3
Go to Step 4
Go to Step 7
Go to Step 8