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Home >> Mitsubishi >> 1999 >> Mirage LS, 2D Coupe, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Circuit Tests >> Scan Tool Will Not Communicate >> No Communication With ECM

No Communication With ECM

  1. Check connectors and wiring harness between ECM and DLC and between ECM and power supply. If wiring and connectors are okay, check MFI relay. See RELAYS in SYSTEM & COMPONENT TESTING article. If MFI relay is okay, go to next step.
  2. Remove MFI relay. Check voltage between ground and MFI relay connector terminal No. 3. If battery voltage exists, go to next step. If battery voltage does not exist, check wiring harness between MFI relay and battery.
  3. Check voltage between ground and MFI relay connector terminal No. 4. If battery voltage exists, go to next step. If battery voltage does not exist, check wiring harness between MFI relay and battery.
  4. For Mirage, go to step  9. On Diamante, disconnect ECM connector B-108 and connector B-109. Turn ignition on. Check voltage between ground and ECM connector terminal No. 20. If battery voltage exists, go to next step. If battery voltage does not exist, check junction connector between MFI relay connector and ECM and wiring harness between ignition switch connector and ECM. If wiring and connectors are okay, check ignition switch.
  5. Check voltage between ground and ECM connector terminal No. 87. If battery voltage exists, go to next step. If battery voltage does not exist, check connectors and wiring harness between ECM and MFI relay.
  6. Check voltage between ground and ECM connector terminal No. 41. If battery voltage exists, go to next step. If battery voltage does not exist, check connectors and wiring harness between ECM and MFI relay.
  7. Turn ignition off. Check continuity between ground and ECM connector terminal No. 42, and ground and terminal No. 48. If continuity exists, go to next step. If continuity does not exist, check connectors and wiring harness between ECM and ground.
  8. Turn ignition on. Check voltage between ground and ECM connector terminal No. 66. If battery voltage exists, check ECM connectors. If ECM connectors are okay, replace ECM and/or TCM. If battery voltage does not exist, check connectors and wiring harness between ECM and battery.
  9. Disconnect ECM connector B-37 and connector B-40. Turn ignition on. Check voltage between ground and ECM connector terminals No. 12 and 25. If battery voltage exists, go to next step. If battery voltage does not exist, check MFI relay connector and ECM and wiring harness between MFI relay connector and ECM.
  10. Turn ignition off. Check continuity between ground and ECM connector terminals No. 13 and 26. If continuity exists, go to next step. If continuity does not exist, check wiring harness between ground and ECM.
  11. Turn ignition on. Check voltage between ground and ECM connector terminal No. 80. If battery voltage exists, check ECM connector. If ECM connector is okay, replace ECM. If battery voltage does not exist, check wiring harness between ECM and battery.
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