Monitor Description

The ECM detects pressure change with the pressure sensor to determine malfunctioning parts in the system, and stores the DTCs. The ECM measures pressure and/or exhaust pulsation of the system at 6 points, A to F, when the air injection system is in operation or when not in operation. When the pressure is high, the ECM determines that the pump operates. When exhaust pulsation is detected, the ECM determines that the Air Switching Valve (ASV) is open. The ECM determines malfunction parts based on the measured value, and stores the DTCs.

Points A and B:

ECM detects pressure changes (decrease), and determines that the No. 2 Air Switching Valve (No. 2 ASV) is open.

Points C and F:

ECM detects pressure and exhaust pulsation, and determines the pressure pattern of the system.

Point D:

ECM operates the system, as indicated by the dashed lines, to determine which of the No. 2 ASV is malfunctioning only when pressure changes cannot be detected at point A or B.

Point E:

ECM detects exhaust pulsation to determine the condition of the system.

Fig 1: Monitor Operation Outline Graph

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Pressure condition in Secondary Air Injection System (Point C and F) 

Pattern 1: 

Pattern 2: 

Pattern 3: 

Pattern 4: 

Judgment and decision of failure mode: