6E1–47
X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
PRIMARY SYSTEM–BASED
DIAGNOSTICS
Primary System–Based Diagnostics
There are primary system–based diagnostics which
evaluate system operation and its effect on vehicle
emissions. The primary system–based diagnostics are
listed below with a brief description of the diagnostic
function:
Oxygen Sensor Diagnosis
The fuel control heated oxygen sensor (HO2S 1) is
diagnosed for the following conditions:
D
Heater performance (time to activity on cold start)
D
Slow response
D
Response time (time to switch R/L or L/R)
D
Inactive signal (output steady at bias voltage –
approx. 450 mV)
D
Signal fixed high
D
Signal fixed low
The catalyst monitor heated oxygen sensor (HO2S 2) is
diagnosed for the following conditions:
D
Heater performance (time to activity on cold start).
D
Signal fixed low during steady state conditions or
power enrichment (hard acceleration when a rich
mixture should be indicated).
D
Signal fixed high during steady state conditions or
deceleration mode (deceleration when a lean mixture
should be indicated).
D
Inactive sensor (output steady at approx. 438 mV).
If the oxygen sensor pigtail wiring, connector or terminal
are damaged, the entire oxygen sensor assembly must
be replaced. DO NOT attempt to repair the wiring,
connector or terminals. In order for the sensor to function
properly, it must have clean reference air provided to it.
This clean air reference is obtained by way of the oxygen
sensor wire(s). Any attempt to repair the wires, connector
or terminals could result in the obstruction of the
reference air and degrade oxygen sensor performance.
Refer to On–Vehicle Service, Heated Oxygen Sensors.
Fuel Control Heated Oxygen Sensors
The main function of the fuel control heated oxygen
sensors is to provide the control module with exhaust
stream oxygen content information to allow proper fueling
and maintain emissions within mandated levels. After it
reaches operating temperature, the sensor will generate
a voltage, inversely proportional to the amount of oxygen
present in the exhaust gases. The control module uses
the signal voltage from the fuel control heated oxygen
sensors while in ”Closed Loop” to adjust fuel injector
pulse width. While in ”Closed Loop”, the ECM can adjust
fuel delivery to maintain an air/fuel ratio which allows the
best combination of emission control and driveability. The
fuel control heated oxygen sensors are also used to
determine catalyst efficiency.
HO2S Heater
Heated oxygen sensors are used to minimize the amount
of time required for ”Closed Loop” fuel control to begin
operation and to allow accurate catalyst monitoring. The
oxygen sensor heater greatly decreases the amount of
time required for fuel control sensor (HO2S 1) to become
active. Oxygen sensor heaters are required by the
catalyst monitor sensor (HO2S 2) to maintain a
sufficiently high temperature which allows accurate
exhaust oxygen content readings further away from the
engine.