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Home >> Toyota >> 2003 >> Matrix Base, FWD, Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System Self Diagnostics >> Diagnostic Tests >> DTC P0171: System Too Lean (Fuel Trim Bank No. 1) & DTC P0172: System Too Rich (Fuel Trim Bank No. 1) >> Diagnosis & Repair

Diagnosis & Repair

NOTE: Read freeze frame data using hand-held tester or OBD II scan tool. Because freeze frame records engine conditions when malfunction is detected, when trouble shooting it is useful for determining whether vehicle was running or stopped, engine warmed up or not, air-fuel ratio lean or rich, etc. at time of malfunction.

For wiring diagram, see DTC P0125: INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED LOOP FUEL CONTROL . For diagnosis and repair, see Fig 1-Fig 3. For testing of systems or components, see BASIC DIAGNOSTIC PROCEDURES - 4-CYL article or SYSTEM & COMPONENT TESTING - 4-CYLINDER article. For vacuum hose routing, see VACUUM DIAGRAMS article. For removal and installation of components, see REMOVAL & INSTALLATION - 4-CYLINDER article. To identify circuits referenced in testing, See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. To check ECM inputs and outputs, see PIN VOLTAGE CHARTS article. To check for intermittent problems, see INTERMITTENT PROBLEM CHECK  under SELF-DIAGNOSTIC SYSTEM.

Fig 1: DTCs P0171 & P0172 Diagnostic Procedure (Steps 1-7)
G00241570Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 2: DTCs P0171 & P0172 Diagnostic Procedure (Steps 8-9)
G00241571Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 3: DTCs P0171 & P0172 Diagnostic Procedure (Steps 10-12)
G00241572Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002