RayTek Rayst25 Autopro User Manual page 18

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Engine Performance (Cont.)
verify ECT and IAT sensor inputs, a scan tool or
other data device with proper software installed
will need to be connected to the vehicle to enable
viewing of the actual ECT and IAT sensor
temperature readings.
Start engine and run until normal operating
temperature of 85-105°C (190-220°F) is reached
and temperature stabilizes. For vehicles
equipped with electric cooling fans, ensure fans
cycle on and off three times prior to checking
temperatures.
To verify ECT sensor temperature, monitor ECT
sensor temperature reading on scan tool. On
most vehicles the ECT sensor is threaded into
the cooling system, near the thermostat.
Measure temperature where ECT sensor threads
into engine. Compare temperature readings. If
temperature readings are not approximately the
same, check for the following before diagnosing:
Damaged ECT sensor, connector or wiring.
Air in cooling system (possibly from not
being properly bled).
To verify IAT sensor temperature, turn engine off
and ignition on. Monitor IAT sensor temperature
reading on scan tool. On some vehicles the IAT
sensor may be threaded into the intake air
ducting before the throttle body. On other
vehicles it may be threaded directly into the
intake manifold after the throttle body. After
engine reaches operating temperature, it may be
difficult to verify IAT sensor temperature when
threaded into the intake manifold. On vehicles
where the IAT is threaded into the intake air
ducting, remove ducting to access IAT sensor
without disconnecting IAT sensor. Measure air
temperature around IAT sensor. Compare
temperature readings. If temperature readings
are not approximately the same, check for the
following before diagnosing:
Contaminated or damaged IAT sensor,
connector or wiring.
Damaged intake air ducting.
Catalytic Converter - Efficiency
An engine may run fine yet fail an emissions test.
The catalytic converter efficiency can be
checked. Start engine and test drive vehicle until
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normal operating temperature of 85-105°C (190-
220°F) is reached and temperature stabilizes. On
some vehicles the catalytic converter
temperatures will lower and become insufficient
for testing purposes if the vehicle is left idling for
a prolonged period of time. For vehicles
equipped with electric cooling fans, ensure fans
cycle on and off three times prior to testing
catalytic converter. During test, hold throttle to
keep engine running at 1000 RPM.
Fig. 6: Measuring Converter Inlet & Outlet
Temperatures
Using the IR thermometer, measure the inlet and
outlet temperatures of the converter. See Fig. 6.
Compare inlet temperature to outlet temperature.
On vehicles equipped with 2-way catalytic
converters, temperature differential will be 55°C
(100°F) or more. On vehicles equipped with 3-
way catalytic converters, temperature differential
will be 20°C (30°F) or more. The outlet
temperature will be hotter when the converter is
operating properly. If temperature differential
between converter inlet and outlet are less than
specified or the application, then the converter
needs to be inspected further. Before replacing
the catalytic converter, determine cause of
failure. Catalytic converters are designed to last
the life of the vehicle. If vehicle has high mileage
of over 240,000 kilometers (150,000 miles) it is
probably just expired. If the vehicle has low
mileage of less 240,000 kilometers (150,000
miles) then check for the following:
Ignition system malfunction (misfire).
Fuel system malfunction (over-lean or
over- rich condition).
Emission system operation (O , air
2
injection, etc).
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