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Engine Control Module Power Source Circuit: Celica

  1. Remove cover for access to Engine Control Module (ECM). ECM is located in engine compartment, below cover, just in front of battery, next to driver's side strut tower. For illustration of ECM location, see THEORY & OPERATION article. Note ECM electrical connector terminals. See Figure.
  2. Turn ignition on. Using voltmeter, check voltage between terminals No. 16 (Black/Red wire) at ECM electrical connector E2 and No. 17 (Brown wire) at ECM electrical connector E4. 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 E4 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 is defective, repair as necessary.
  3. Ensure ignition is on. Using voltmeter, check voltage between body ground and terminal No. 8 (Black/Orange wire) at ECM electrical connector E2. 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  5.
  4. Check ignition switch. See IGNITION SWITCH  under ENGINE SENSORS & SWITCHES. If ignition switch is defective, replace ignition switch. See IGNITION SWITCH under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article. If ignition switch is okay, check for open and short in wiring harness and electrical connectors between battery and ignition switch, and between ignition switch and terminal No. 8 (Black/Orange wire) at ECM electrical connector E2. See WIRING DIAGRAMS article. If necessary to check AM2 fuse, AM2 fuse is located in fuse/relay box at driver's side front corner of engine compartment, just in front of strut tower. Repair wiring harness or electrical connectors as necessary.
  5. 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.
  6. Check for defective EFI fuse. EFI fuse is located in fuse/relay box at driver's side front corner of engine compartment, just in front of strut tower. If EFI fuse is okay, go to next step. If EFI fuse is defective, repair short in wiring harness between battery and EFI fuse. See WIRING DIAGRAMS article.
  7. Check for defective EFI No. 1 fuse. EFI No. 1 fuse is located in fuse/relay box at driver's side front corner of engine compartment, just in front of strut tower. EFI No. 1 fuse may also be referred to as EFI1 fuse. If EFI No. 1 fuse is okay, go to next step. If EFI No. 1 fuse is defective, repair short in wiring harness and components connected to EFI No. 1 fuse. See WIRING DIAGRAMS article.
  8. Check for open and short in wiring harness and electrical connectors between terminal No. 21 (Blue/Black wire) at ECM electrical connector E3 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 is defective, repair as necessary.
  9. Check wiring harness and electrical connectors between battery and EFI fuse, and between EFI No. 1 fuse and terminal No. 16 (Black/Red wire) at ECM electrical connector E2. Repair wiring harness or and electrical connectors as necessary.
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