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Engine Control Module Power Source Circuit: MR2

  1. Remove necessary components for access to Engine Control Module (ECM). ECM is located on inside of firewall, directly behind driver's seat and luggage compartment. See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  2. Remove bolts and disconnect ECM with electrical connectors from inside of firewall. Note ECM electrical connector terminals. See Figure.
  3. Turn ignition on. Using voltmeter, check voltage between terminals No. 16 (Black 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.
  4. Turn ignition off. Check for open and short in Black wire between EFI main relay and terminal No. 16 at ECM electrical connector E2. See WIRING DIAGRAMS article. EFI main relay is located in relay box on firewall at driver's side front corner of engine compartment. If wiring is okay, go to next step. If wiring is defective, repair as necessary.
  5. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 8 (Black/Red 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  11.
  6. Check for defective IG2 fuse. IG2 fuse is located in fuse/relay box at driver's side rear corner of engine compartment, just in front of strut tower. If IG2 fuse is okay, go to next step. If IG2 fuse is defective, repair short in wiring harness and components connected to IGN fuse. See WIRING DIAGRAMS article.
  7. Check operation of IG2 relay. See IG2 RELAY  under MODULES, MOTORS, RELAYS & SOLENOIDS. If IG2 relay operates properly, go to next step. If IG2 relay is defective, replace IG2 relay.
  8. Check for defective AM2 fuse. AM2 fuse is located in fuse/relay box at driver's side rear corner of engine compartment, just in front of strut tower. 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.
  9. Check ignition switch. See IGNITION SWITCH  under ENGINE SENSORS & SWITCHES. If ignition switch is okay, go to next step. If ignition switch is defective, replace ignition switch. See IGNITION SWITCH under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  10. Check for open in wiring harness and electrical connectors between battery and ignition switch, battery and IG2 relay, ignition switch and IG2 relay, and between IG2 relay and terminal No. 8 (Black/Red wire) at ECM electrical connector E2. See WIRING DIAGRAMS article. Repair wiring harness or electrical connectors as necessary.
  11. Ensure ignition is on. Using voltmeter, check voltage between body ground and terminal No. 21 (Gray wire) at ECM electrical connector E3. 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.
  12. Check for defective EFI No. 1 fuse. EFI No. 1 fuse is located in fuse/relay box at driver's side rear 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.
  13. 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.
  14. Check for open and short in wiring harness and electrical connectors between terminal No. 21 (Gray 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.
  15. Check wiring harness and electrical connectors between battery and EFI No. 1 fuse, and between EFI No. 1 fuse and EFI main relay. See WIRING DIAGRAMS article. Repair wiring harness or and electrical connectors as necessary.
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