Diagnostic Trouble Code (Dtc) P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1) - Isuzu 1999 RODEO Workshop Manual

6E1–144 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
DIAGNOSTIC TROUBLE CODE (DTC) P0131 O2 SENSOR CIRCUIT LOW VOLT-
Circuit Description
The powertrain control module (PCM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal and low circuits. When measured
with a 10 megaW digital voltmeter, this may display as low
as 350 mV. The oxygen sensor varies the voltage within a
range of about 1000 mV when the exhaust is rich, down
through about 10 mV when exhaust is lean. The PCM
constantly monitors the HO2S signal during "Closed
Loop" operation and compensates for a rich or lean
condition by decreasing or increasing injector pulse width
as necessary. If the Bank 1 HO2S 1 voltage remains
excessively low for an extended period of time,
Diagnostic Trouble Code P0131 will be set. DTC P0131 is
a type A code.
Conditions for Setting the DTC
f No related Diagnostic Trouble Codes.
f Vehicle is operating in "Closed Loop".
f Engine coolant temperature is above 60°C (140°F)
f "Closed Loop" commanded air/fuel ratio is between
14.5 and 14.8.
f Throttle angle is between 3% and 19%.
All above conditions met for 0.3 seconds and the following
condition is met:
f Bank 1 HO2S 1 signal voltage remains below 22 mV
during normal "Closed Loop" operation for a total of
76.5 seconds over a 90–second period of time.
AGE (BANK 1 SENSOR 1)
Action Taken When the DTC Sets
f The PCM will illuminate the malfunction indicator lamp
(MIL) the first time 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.
f "Open Loop" fuel control will be in effect.
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 Diagnostic Trouble Code P0131 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
f Diagnostic Trouble Code P0131 can be cleared by
using the Scan Tool's "Clear Info" function.
Diagnostic Aids
Check for the following conditions:
f Heated oxygen sensor wiring – The sensor pigtail may
be routed incorrectly and/or contacting the exhaust
system. Also, check for shorts to ground, shorts to
battery positive and open circuits.
f Poor PCM to engine block grounds.
f Fuel pressure – The system will go lean if pressure is
too low. The PCM can compensate for some decrease.
However, if fuel pressure is too low, a Diagnostic
D06RX046