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Engine Control Module Power Source Circuit: Avalon

  1. Remove glove box for access to ECM. For illustration of ECM location, see THEORY & OPERATION article. Note ECM electrical connector terminal identification. See Figure.
  2. Turn ignition on. Using voltmeter, check voltage between terminals No. 16 (Black/White wire) at ECM electrical connector E8 and No. 17 (Brown wire) at ECM electrical connector E5. This is the +B and E1 terminals at ECM. Voltage should be 9-14 volts. If voltage is within specification, diagnose by symptom. See TROUBLE SHOOTING - NO CODES article. If voltage is not within specification, check for open in wiring harness and electrical connectors between terminal No. 17 (Brown wire) at ECM electrical connector E5 and body ground. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector are defective, repair as necessary.
  3. Ensure ignition is on. Using voltmeter, check voltage between body ground and terminal No. 2 (Black/Orange wire) at ECM electrical connector E8. This is the IGSW terminal at ECM. Voltage should be 9-14 volts. If voltage is not within specification, go to next step. If voltage is within specification, go to step  7.
  4. Check for defective AM2 fuse. AM2 fuse is located in fuse/relay box at driver's side front corner of engine compartment, near battery. If AM2 fuse is okay, go to next step. If AM2 fuse is defective, repair short in wiring harness and components connected to AM2 fuse. See WIRING DIAGRAMS article.
  5. Check ignition switch. See appropriate STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT. If ignition switch is okay, go to next step. If ignition switch is defective, replace ignition switch.
  6. Check for open in wiring harness and electrical connectors between battery and ignition switch, and between ignition switch and terminal No. 2 (Black/Orange wire) at ECM electrical connector E8. See WIRING DIAGRAMS article. Repair wiring harness or electrical connectors as necessary.
  7. Ensure ignition is on. Using voltmeter, check voltage between body ground and terminal No. 8 (Blue/Orange wire) at ECM electrical connector E8. This is the MREL terminal at ECM. Voltage should be 9-14 volts. If voltage is within specification, go to next step. If voltage is not within specification, check ECM ground circuit. See WIRING DIAGRAMS article. If ECM ground circuit is defective, repair ground circuit as necessary. If ECM ground circuit is okay, replace ECM. On models equipped with engine immobilizer system, if ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. Models equipped with engine immobilizer system may be identified by looking at the ignition key. On models equipped with engine immobilizer system, the top of the ignition key is thicker than a standard ignition key, as a transponder chip is incorporated into the top of the ignition key. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT.
  8. Check for defective EFI No. 1 and 2 fuses. EFI No. 1 and 2 fuses are located in fuse/relay box at driver's side front corner of engine compartment, near battery. If EFI No. 1 and 2 fuses are okay, go to next step. If EFI No. 1 fuse or EFI No. 2 fuse is defective, repair short in wiring harness and components connected to the appropriate EFI fuse. See WIRING DIAGRAMS article.
  9. Check operation of EFI main relay. See EFI MAIN RELAY  under MODULES, MOTORS, RELAYS & SOLENOIDS. If EFI main relay operates properly, go to next step. If EFI main relay is defective, replace EFI main relay.
  10. Check for open and short in wiring harness and electrical connectors between terminal No. 8 (Blue/Orange wire) at ECM electrical connector E8 and EFI main relay, and for open in White/Black wire between EFI main relay and body ground. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector are defective, repair as necessary.
  11. Check wiring harness and electrical connectors between battery and EFI No. 1 fuse. See WIRING DIAGRAMS article. Repair wiring harness or electrical connectors as necessary.
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