EG–438 ENGINE – 2JZ–GE ENGINE TROUBLESHOOTING DTC 31 Volume Air Flow Meter Circuit CIRCUIT DESCRIPTION As shown in the figure at right, when a pillar (Vortex generating body is placed in the path of a uniform flow, vortices called Karman–Vortex are generated downstream of the object. Using this principle, a vortex generator is placed inside the volume air flow meter. By measuring the frequency of the vortices generated, the ECM can determine the volume of air flowing through the volume air flow meter. The vortices are detected by their exerting pressure on thin metal foil mirror) surfaces and a light emitting element and light receptor (LED and photo transistor) positioned opposite the mirror which optically senses the vibrations in the mirror. The ECM uses these signals mainly for calculation of the basic injection volume and the basic ignition advance angle. Karman-Vortex Leaf Spring Luminous Diode Mirror Air Flow Karman-Vortex Vortex Generating Object Pressure Directing Hole Photo Transistor FI3045 FI4504 DTC No. | Diagnostic Trouble Code Detecting Condition | Trouble Area 31 All conditions below are detected: (a) No volume air flow meter signal to ECM for 2 sec. when engine speed is above 300 rpm (b) Engine stall • Open or short in volume air flow meter circuit • Volume air flow meter • ECM if the ECM detects diagnostic trouble code "31", it operates the fail safe function, keeping the ignition timing and fuel injection volume constant and making it possible to drive the vehicle. WIRING DIAGRAM Volume Air Flow Meter 4 L-R 41 E9 VCC 5 V 5 BR 3 LG-B 66 E9 KS 5 V BR 69 E9 E1 BR ED Engine Control Module FI6880