Page 101 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Chapter 1.4

Toyota Motor Co. Ltd.

Toyota has presented since 1990 a significant number of methods concerning diagnostic
methods of deterioration of catalytic converters. Most of these methods, except otherwise
mentioned, have been applied for an engine layout similar to that of fig. 40.

In fig. 40, an air-intake passage of the engine is provided with a potentiometer-type airflow
meter for detecting an amount of air drawn into the engine and generates an analog voltage
signal proportional to the amount of air flowing through. The signal from the air-flow meter is
transmitted to a multiplexer incorporating analog-to-digital (AD) converter of the control
circuit.
Crank angle sensors, for detecting the angle of the crankshaft (not shown) of the engine, are
disposed at a distributor. The first of the crank angle sensors generates a pulse signal at every
720 DEG crank angle (CA) and the second crank angle sensor generates a pulse signal at every
30 DEG CA. The pulse signals from the crank angle sensors are supplied to an input/output
(VO) interface of the control circuit. Further, the pulse signal of the second crank angle sensor
is then supplied to an interruption terminal of a central processing unit (CPU) .
In the air intake passage, a fuel injection valve is provided at an inlet port of each cylinder of
the engine, for supplying pressurized fuel from the he1 system to the cylinders of the engine.

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