Diagnostic Trouble Code (Dtc) P0135 Ho2S Heater Circuit Bank 1 Sensor 1 - Isuzu 1999 RODEO Workshop Manual

6E2–174
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0135 HO2S Heater Circuit Bank 1 Sensor 1

Circuit Description
Heated oxygen sensors are used to minimize the amount
of time required for "closed loop" fuel control operation
and to allow accurate catalyst monitoring. The oxygen
sensor heater greatly decreases the amount of time
required for fuel control sensors Bank 1 HO2S 1 and Bank
2 HO2S 1 to become active. Oxygen sensor heaters are
required by post-catalyst monitor sensors to maintain a
sufficiently high temperature which allows accurate
exhaust oxygen content readings further from the engine.
The powertrain control module (PCM) will run the heater
test only after a cold start (determined by engine coolant
and intake air temperature at the time of start-up) and only
once during an ignition cycle. When the engine is started
the PCM will monitor the HO2S voltage. When the HO2S
voltage indicates a sufficiently active sensor, the PCM
looks at how much time has elapsed since start-up. If the
PCM determines that too much time was required for the
Bank 1 HO2S 1 to become active, a DTC P0135 will set.
The time it should take the HO2S to reach operating
temperature is based on the accumulated amount of air
that has passed through the MAF sensor and into the
engine (more accumulated air flow = shorter time to
HO2S activity).
Conditions for Setting the DTC
f No related DTCs.
f Intake air temperature (IAT) is less than 32°C (90°F)
at start-up.
f Engine coolant temperature (ECT) is less than 32°C
(90°F) at start-up.
f IAT and ECT are within 6°C (11°F) of each other at
start-up.
f Ignition voltage is between 11 and 18 V.
f Average mass air flow is less than 21 g/second during
sample period.
f Bank 1 HO2S 1 voltage does not change more than
150 mV from the bias voltage (between 400 mV and
500 mV) for a longer amount of time than it should. The
maximum amount of time to come up to operating
range is 150 seconds. This warm-up time depends on
the engine coolant temperature at start-up and
accumulate air flow since start-up.
Action Taken When the DTC Sets
f The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
f The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
f The PCM will turn the MIL "OFF" on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
f A history DTC P0135 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
D06RW060