Isuzu 2000 Trooper UX, Workshop Manual

Page: 1063 / 2150

6E–194
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0141 HO2S Heater Circuit Bank 1 Sensor 2
D06RY00173
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 Bank
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 2 to become active, a DTC P0141
will set. The time it should take the HO2S to reach
operating temperature is based on the total amount of air
that has passed through the MAF sensor and into the
engine (more total airflow = shorter time to HO2S
activity).
Conditions for Setting the DTC
D
No related DTCs.
D
Intake air temperature (IAT) is less than 32
°
C (90
°
F)
at start-up.
D
Engine coolant temperature (ECT) is less than 32
°
C
(90
°
F) at start-up.
D
IAT and ECT are within 6
°
C (11
°
F) of each other at
start-up.
D
Ignition voltage is between 11 volts and 18 volts.
D
Average mass airflow is less than 23 g/second during
the sample period.
D
Bank 1 HO2S 2 voltage does not change more than
150 mV from the bias voltage (between
400 mV–500 mV) for a longer amount of time than it
should. The maximum amount of time to come up to
operating range is 120 seconds. This warm-up time
depends on the engine coolant temperature at start-up
and accumulated air flow since start-up.
Action Taken When the DTC Sets
D
The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
D
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
D
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.
D
A history DTC P0141 will clear after 40 consecutive
warm-up cycles have occurred without a fault.