Isuzu 1999 RODEO Workshop Manual page 795

6E1–168 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
DIAGNOSTIC TROUBLE CODE (DTC) P0141 O2 SENSOR HEATER CIRCUIT
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 catalyst monitor sensors Bank 1 HO2S 2 and
Bank 2 HO2S 2 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
Diagnostic Trouble Code P0141 will set. DTC P0141 is a
type B code.
Conditions for Setting the DTC
f No related Diagnostic Trouble Codes.
f Intake air temperature (IAT) is less than 32°C (90°F)
at start–up.
MALFUNCTION (BANK 1 SENSOR 2)
f Engine coolant temperature (ECT) is less than 32°C
(90°F) at start–up.
f IAT and ECT are within 5°C (9°F) of each other at
start–up.
f Ignition voltage is between 11 volts and 16.6 volts.
f Throttle angle is less than 40%.
f Average calculated airflow is less than 18 g/second
during the sample period.
f Bank 1 HO2S 2 voltage does not change more than
148 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 405 seconds. This warm–up time depends on
the engine coolant temperature at start–up and intake
air temperature at 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 Diagnostic Trouble Code 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 duringwhich the diagnostic has been run and
the fault condition is no longer present.
D06RX047