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Home >> Mitsubishi >> 2002 >> Diamante LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Circuit Check >> Scan Tool Will Not Communicate >> No Communication With PCM

No Communication With PCM

  1. Check connectors and wiring between PCM and OBD-II Data Link Connector (OBD-II DLC). Check wiring and connectors between PCM and power supply. Repair as necessary. If problem does not exist, go to next step.
  2. Check MFI relay. See RELAYS under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. If MFI relay is defective, replace MFI relay. If MFI relay is okay, go to next step.
  3. Remove MFI relay. Measure voltage between ground and MFI relay connector terminal No. 3. See Figure. If battery voltage is present, go to next step. If battery voltage is not present, repair wiring between MFI relay and battery.
  4. Measure voltage between ground and MFI relay connector terminal No. 4. If battery voltage is present, go to next step. If battery voltage is not present, repair wiring between MFI relay and battery.
  5. Install MFI relay. Disconnect PCM 35-pin connector B-108 and PCM 26-pin connector B-109. Turn ignition on. Measure voltage between ground and PCM connector B-108 terminal No. 21 (White/Red wire). See Figure. If battery voltage is present, go to next step. If battery voltage is not present, repair White/Red wire between fuel pump relay and PCM.
  6. Measure voltage between ground and PCM connector B-109 terminal No. 49 (Black/White wire). If battery voltage is present, go to next step. If battery voltage is not present, repair Black/White wire between MFI relay and PCM.
  7. Energize MFI relay by connecting jumper wire between ground and PCM connector B-109 terminal No. 49 (Black/White wire). Measure voltage between ground and PCM connector terminals No. 41 (Red wire) and No. 47 (Red wire). If battery voltage is present at each terminal, go to next step. If battery voltage is not present at each terminal, repair appropriate Red wire between PCM and MFI relay.
  8. Turn ignition off. Disconnect jumper wire. Check continuity between ground and PCM connector B-109 terminals No. 42 (Black wire) and No. 48 (Black wire). If continuity exists at each terminal, go to next step. If continuity does not exist at each terminal, repair appropriate Black wire between ground and PCM.
  9. Measure voltage between ground and PCM connector B-109 terminal No. 66 (White/Black wire). If battery voltage is present, replace PCM. If battery voltage is not present, repair circuit between PCM and battery.
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