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Camry CNG Models

  1. Remove glove box for access to Engine Control Module (ECM). 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/Yellow wire) at ECM electrical connector E4 and No. 17 (Brown wire) at ECM electrical connector E6. 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 E6 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. Turn ignition off. Check for open and short in Black/Yellow wire between EFI main relay and terminal No. 16 (Black/Yellow wire) at ECM electrical connector E4. See WIRING DIAGRAMS article. EFI main relay is located in fuse/relay box at driver's side front corner of engine compartment, near battery. If wiring is okay, go to next step. If wiring is defective, repair as necessary.
  4. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 19 (Black/Red wire) at ECM electrical connector E5. 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  8.
  5. Check for defective IGN fuse. IGN fuse is located in fuse box behind driver's side of instrument panel. If IGN fuse is okay, go to next step. If IGN fuse is defective, repair short in wiring harness and components connected to IGN fuse. See WIRING DIAGRAMS article.
  6. 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.
  7. Check for open and short in wiring harness and electrical connectors between battery and ignition switch, and between ignition switch and terminal No. 19 (Black/Red wire) at ECM electrical connector E5. See WIRING DIAGRAMS article. Repair wiring harness or electrical connectors as necessary.
  8. Ensure ignition is on. Using voltmeter, check voltage between body ground and terminal No. 21 (Black/White wire) at ECM electrical connector E4. 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.
  9. Check for defective EFI fuse. EFI fuse is located in fuse/relay box at driver's side front corner of engine compartment, near battery. If EFI fuse is okay, go to next step. If EFI fuse is defective, repair short in wiring harness and components connected to EFI fuse. See WIRING DIAGRAMS article.
  10. 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.
  11. Check for open and short in wiring harness and electrical connectors between terminal No. 21 (Black/White wire) at ECM electrical connector E4 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.
  12. Check wiring harness and electrical connectors between battery and EFI fuse. See WIRING DIAGRAMS article. Repair wiring harness or and electrical connectors as necessary.
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