P0140 Ho2S Circuit Insufficient Activity Bank 1 Sensor 2 - Isuzu 2000 Trooper Workshop Manual

P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2

Circuit Description
To control emissions of hydrocarbons (HC), carbon
monoxide (CO), and oxides of nitrogen (NOx), a
three-way catalytic converter is used. The catalyst within
the converter promotes a chemical reaction which
oxidizes the HC and CO present in the exhaust gas,
converting them into harmless water vapor and carbon
dioxide. The catalyst also reduces NOx, converting it to
nitrogen. The powertrain control module (PCM) has the
ability to monitor this process using the Bank 1 HO2S 1
and the Bank 1 HO2S 2 heated oxygen sensors. The
Bank 1 HO2S 2 sensor produces an output signal which
indicates the amount of oxygen present in the exhaust
gas entering the three-way catalytic converter. The Bank
1 HO2S 2 sensor produces an output signal which
indicates the oxygen storage capacity of the catalyst; this
in turn indicates the catalyst's ability to convert exhaust
gases efficiently. If catalyst is operating efficiently, the
Bank 1 HO2S 1 signal will be far more active than that
produced by the Bank 1 HO2S 2 sensor. If the Bank 1
HO2S 2 signal voltage remains between 400 mV and
500 mV for an extended period of time, DTC P0140 will be
set. 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.
heaters are required by post-catalyst monitor sensors to
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code(DTC)
Oxygen sensor
maintain a sufficiently high temperature for accurate
exhaust oxygen content readings further from the engine.
Conditions for Setting the DTC
D No related DTCs.
D Battery voltage is above 10 volts.
D Engine run time is longer than 40 seconds.
D Oxygen sensor heater is functioning properly.
D Engine is operating in "closed loop"
D Bank 1 HO2S 2 signal voltage remains between
426 mV and 474 mV for a total of 106 seconds over a
125-second period of time.
Action Taken When the DTC Sets
D The PCM will illuminate the malfunction indicator lamp
(MIL) the first time 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 Cleaning 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 P0140 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
D DTC P0140 can be cleared by using the Tech 2 "Clear
Info" function or by disconnecting the PCM battery
feed.
6E–191
D06RY00173