1999 Lexus ES 300FACTORY OEM SERVICE PROCEDURE

ECM Power Source Circuit (Ignition Keyed): Es300

  1. Access ECM behind glove box. Turn ignition on. Backprobing connector, connect DVOM negative lead to terminal No. 17 (Brown wire) at ECM E10 connector and positive lead to terminal No. 16 (Black/Yellow wire) at ECM E7 connector. See Fig 1. If 9-14 volts is present, ECM power circuit is okay. Diagnose by symptom. See TROUBLE SHOOTING - NO CODES article. If 9-14 volts is not present, go to next step.
  2. Check for an open circuit in Brown wire between ground and terminal 17 at ECM E10 connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, go to next step.
  3. Measure voltage between chassis ground and terminal No. 2 (Black/Red wire) at ECM E7 connector. If 9-14 volts is present, go to step  5. If 9-14 volts is not present, check IGN fuse in instrument panel junction box under left side of instrument panel.
  4. If fuse is blown, repair cause of blown fuse. If fuse is okay, check ignition switch. See STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT. Replace ignition switch as necessary and retest. If ignition switch is okay, repair open circuit between battery and ignition switch, or between ignition switch and ECM.
  5. Turn ignition on. Measure voltage between chassis ground and terminal 8 (Black/White wire) at ECM E7 connector. If 9-14 volts is not present, replace ECM. If 9-14 volts is present, check EFI fuse located in engine compartment fuse/relay box at left front of engine compartment. If fuse is okay, go to next step. If EFI fuse is blown, repair cause of blown fuse.
  6. Check EFI main relay located in engine compartment fuse/relay box at left front of engine compartment. See RELAYS  under RELAYS & SOLENOIDS. If EFI main relay is okay, check circuit between chassis ground and terminal No. 8 at ECM E7 connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, repair circuit between battery and EFI fuse.
Fig 1: Identifying Electronic Control Module (ECM) Connector Terminals (ES300)
G99G51322Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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