Suzuki XL7 2007 Service Manual page 169

Circuit Description
The heated oxygen sensor (HO2S) heater reduces the
time required for the oxygen sensor to reach operating
temperature and maintains the operating temperature
during extended idle periods. When the ignition is turned
to the ON position, ignition voltage is supplied directly to
the sensor heater. The engine control module (ECM)
controls the heater operation by first modulating the
control circuit to ground when the sensors are cold. This
prevents the possibility of thermal shock to the sensor,
from condensation build-up on the sensor, by controlling
the sensors rate of heating. After a predetermined
amount of time, the ECM commands the heaters ON
continuously. Once the sensor reaches operating
temperature, the ECM may modulate the heater control
circuit to ground, to maintain a desired temperature.
The ECM controls the heater by grounding the control
circuit with a solid state device called a driver. The driver
is equipped with a feedback circuit that is pulled-up to
voltage. The ECM can determine if the control circuit is
open, shorted to ground, or shorted to a voltage by
monitoring the feedback voltage.
The HO2S utilizes the following circuits:
• A signal circuit
• A low reference circuit
• An ignition voltage circuit
• A heater control circuit
Conditions for Running the DTC
P0030, P0031, P0032, P0050, P0051, P0052
• The ignition voltage is between 10.5-18 volts.
• The engine speed is more than 80 RPM.
• The HO2S heater is commanded ON and OFF at
least once during the ignition cycle.
• The DTCs run continuously once the above conditions
are met for 1 second.
P0036, P0037, P0038, P0056, P0057, P0058
• The ignition voltage is between 10.5-18 volts.
• The engine speed is more than 80 RPM.
• The HO2S heater is commanded ON and OFF at
least once during the ignition cycle.
• The secondary HO2S is at operating temperature.
• The DTCs run continuously once the above conditions
are met for 1 second.
Engine General Information and Diagnosis:
Conditions for Setting the DTC
P0030, P0036, P0050, and P0056
The ECM detects an open in the heater circuits of the
HO2S when the heater is commanded OFF. The
condition exists for more than 4 seconds or a cumulative
of 50 seconds.
P0031, P0037, P0051, and P0057
The ECM detects a ground in the heater circuits of the
HO2S when the heater is commanded OFF. The
condition exists for more than 4 seconds or a cumulative
of 50 seconds.
P0032, P0038, P0052, and P0058
The ECM detects a short to voltage in the heater circuits
of the HO2S when the heater is commanded ON. The
condition exists for more than 4 seconds or a cumulative
of 50 seconds.
Action Taken When the DTC Sets
DTCs P0030, P0031, P0032, P0036, P0037, P0038,
P0050, P0051, P0052, P0056, P0057, and P0058 are
Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0030, P0031, P0032, P0036, P0037, P0038,
P0050, P0051, P0052, P0056, P0057, and P0058 are
Type B DTCs.
Diagnostic Aids
• If the condition is intermittent, move the related
harnesses and connectors, with the engine operating,
while monitoring the circuit status for the component
with a scan tool. The circuit status parameter changes
from OK or Indeterminate to Fault if there is a
condition with the circuit or a connection.
• An open fuse in the HO2S heater circuit may be
caused by the heater element in one of the sensors.
The condition may not be present until the sensor
operates for a period of time. If no fault is present in
the heater circuit, monitor the amperage of each
heater using the DMM to determine if one of the
heater elements is the cause of the open fuse. Inspect
the sensor pigtail or the harness for contacting the
exhaust system.
1A-64