Diagnosis & Repair

NOTE: Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

After confirming DTC P0125, use Toyota hand-held tester or scan tool to access CURRENT DATA to read output voltage for A/F sensors. The ECM controls the voltage of AF1A+/AF2A+ and AF1A-/AF2A- terminals of the ECM to the fixed voltage. Therefore, it is impossible to confirm the A/F sensor output voltage without the OBD II scan tool or TOYOTA hand-held tester. A/F sensor output voltage on scan tool is displayed at one fifth the voltage of that displayed on a Toyota hand-held tester.

For diagnosis and repair procedure, see Fig 1-Fig 6 . For A/F sensor circuit wiring diagram, see Figure. For location of A/F sensors, see Fig 7.

When instructed to "Perform Confirmation Driving Pattern", go to TEST DRIVE CONFIRMATION procedure.

When access to, or replacement of ECM is necessary, Engine Control Module (ECM) is located behind glove box. See Figure. For ECM connector terminal view, see Figure.

For vacuum or EVAP hose routing, see VACUUM DIAGRAMS article. For testing of systems or components, see BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article or SYSTEM & COMPONENT TESTING - 4-CYLINDER article. For removal and installation of components, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

Fig 1: DTC P0125 Diagnostic Procedure (Steps 1-3)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 2: DTC P0125 Diagnostic Procedure (Step 3 Cont.)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 3: DTC P0125 Diagnostic Procedure (Step 3 Cont. & Steps 4-8)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 4: DTC P0125 Diagnostic Procedure (Step 8 Cont. & Steps 9-12)

Fig 5: DTC P0125 Diagnostic Procedure (Steps 13-17)

Fig 6: DTC P0125 Diagnostic Procedure (Steps 18-19)

Fig 7: Locating A/F Sensors & Heated Oxygen Sensors