{"model":"mk4","model_name":"MK4 Supra","vehicle":"Toyota Supra A80 (1993–2002, 2JZ-GE / 2JZ-GTE)","document":"Repair Manual","section":"TGTE","section_name":"Troubleshooting 2JZ-GTE","page":58,"pages_in_section":113,"title":"Dtc 31 Mass Air Flow Meter Circuit","section_header":"Engine — 2JZ–GTE Engine Troubleshooting","ocr_text":"EG–544\n\nENGINE – 2JZ–GTE ENGINE TROUBLESHOOTING\n\nDTC 31 Mass Air Flow Meter Circuit\n\nCIRCUIT DESCRIPTION\n\nThe mass air flow meter is an air flow meter which uses a platinum hot wire. The hot wire air flow meter works on the principle that when the electrically heated platinum hot wire is positioned inside the intake air bypass, the intake air volume can be calculated according to the change in the hot wire temperature. This change in temperature is measured by the thermistor at the rear of the hot wire. And feedback from the circuit maintains the hot wire at a set temperature by controlling the current flowing through the hot wire. This current flow is then measured as the output voltage of the air flow meter. The circuit is constructed so that the platinum hot wire and the thermistor provide a bridge circuit, with the power transistor controlled so that the potential of (A) or (B) remains equal to maintain the set temperature.\n\nB+\nPower Transistor\nThermistor\nPlatinum Hot Wire\nA\nB\nOutput Voltage\n\nFI6929\nFI6972\n\nPlatinum Hot Wire\nThermistor\n\nDTC No. | Diagnostic Trouble Code Detecting Condition | Trouble Area\n\n31 | Open or short in mass air flow meter circuit for 3 sec. or more with engine speed less than 3,000 rpm | • Open or short in mass air flow master circuit\n• Mass air flow meter\n• ECM\n\nIf the ECM detects diagnostic trouble code \"31\", it operates the fail safe function whereby the turbo pressure sensor is used, making it possible to continue to drive the vehicle.\n\nWIRING DIAGRAM\n\nR/B No.2\nEngine Control Module\n2  3  5  2  B-R\nB+\n2  2  1  2  GR\n8  GR  24\nEA1  E10  M-REL\nEFI Main Relay\n5 EA2\nB-Y\nR/B No.2\nW-B\nEFI No.1\n2A\nB\nBattery\n\nY-R  66  VG\n2  E9\nBR  28\n5  E9  E21\nE1\n\nMass Air Flow Meter\n\nFI6830","image":"https://tsrm.sasquatchvc.com/images/mk4/TGTE/TGTE_058.png","url":"https://tsrm.sasquatchvc.com/mk4/tsrm/TGTE/58","prev":{"page":57,"url":"https://tsrm.sasquatchvc.com/mk4/tsrm/TGTE/57","api":"https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/57"},"next":{"page":59,"url":"https://tsrm.sasquatchvc.com/mk4/tsrm/TGTE/59","api":"https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/59"},"section_url":"https://tsrm.sasquatchvc.com/mk4/tsrm/TGTE","section_api_pages":["https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/1","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/2","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/3","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/4","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/5","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/6","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/7","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/8","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/9","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/10","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/11","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/12","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/13","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/14","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/15","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/16","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/17","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/18","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/19","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/20","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/21","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/22","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/23","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/24","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/25","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/26","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/27","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/28","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/29","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/30","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/31","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/32","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/33","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/34","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/35","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/36","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/37","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/38","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/39","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/40","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/41","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/42","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/43","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/44","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/45","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/46","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/47","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/48","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/49","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/50","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/51","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/52","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/53","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/54","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/55","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/56","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/57","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/58","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/59","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/60","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/61","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/62","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/63","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/64","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/65","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/66","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/67","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/68","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/69","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/70","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/71","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/72","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/73","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/74","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/75","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/76","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/TGTE/77","https://tsrm.sasquatchvc.com/api/pages/mk4/tsrm/T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transcript of a scanned Toyota factory manual page; verify critical values (torque specs, part numbers) against the image."}