9-5 Sedan (9600) L4-2.3L Turbo (B235) (2000)
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Exhaust Temperature Sensor: Description and Operation
Temperature Warning For Overheated Three-Way Catalytic Converter
To meet the legal requirements for grass fire protection, a monitoring system is fitted to cars for the Japanese market.
The system consists of a temperature sensor in the catalytic converter, a relay on the main relay board in the dashboard and a warning lamp in the main
instrument unit. When the catalytic converter temperature reaches 825°C ±25°C (1517°F ±45°F), the warning lamp comes on. It does not go out until
the temperature falls by 10°C (18°F).
A fire-prevention shield is fitted under the three-way catalytic converter to prevent the ground vegetation catching fire.
Description of Operation
When a voltage of +15 V is applied to relay pin 4 (i.e. when the ignition is switched on), the relay grounds the warning lamp for about 3 seconds.
Normally the warning lamp then goes out and does not come on again until the catalytic converter temperature exceeds the specified value. If the lamp
does not go out, a break in the temperature sensor circuit is indicated. When the voltage applied constantly to temperature sensor pins 1 and 2 reaches a
specific value due to changes in the sensor resistance as the temperature rises, the relay is activated and the lamp lights. Similarly, the lamp goes out
when the temperature falls or when the voltage of +15 V is interrupted (i.e. when the ignition is turned off).
