LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mitsubishi >> 2000 >> Galant LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Circuit Tests >> Scan Tool Will Not Communicate >> No Communication With ECM/PCM
April 5, 2026: LEMON Manuals is launched! Read the announcement.

No Communication With ECM/PCM

  1. Check wiring and intermediate connectors between OBD-II Data Link Connector (OBD-II DLC) and Engine Control Module (ECM) 12-pin connector C-37, or Powertrain Control Module (PCM) 28-pin connector C-41. If problem exists, repair as necessary. If problem does not exist, go to next step.
  2. Check ECM connector C-37 or PCM connector C-41. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Remove and check MFI relay. See FUEL PUMP RELAY & MFI RELAY under RELAYS under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. If problem exists, replace MFI relay. If problem does not exist, go to next step.
  4. Check voltage between ground and MFI relay connector terminals No. 3 and 4. If battery voltage exists at both terminals, go to next step. If battery voltage does not exist at either or both terminals, repair wiring between battery and MFI relay.
  5. Disconnect ECM connector C-38 or PCM connector C-41. Turn ignition on. Check voltage between ground and ECM connector C-38 terminal No. 82, or PCM connector C-41 terminal No. 98. If battery voltage exists, go to next step. If battery voltage does not exist, check wiring between ignition switch and ECM/PCM. If problem exists, repair wiring between ignition switch and ECM/PCM. If problem does not exist, check ignition switch.
  6. Turn ignition off. On 2.4L A/T and 3.0L vehicles, disconnect PCM 26-pin connector C-40. On all vehicles, turn ignition on. Check voltage between ground and ECM connector C-38 terminal No. 80, or PCM connector C-40 terminal No. 66. If battery voltage exists, go to next step. If battery voltage does not exist, repair wiring between battery and ECM/PCM.
  7. Turn ignition off. On 2.4L M/T vehicles, disconnect ECM 26-pin connector C-35. On all vehicles, check resistance between ground and ECM connector C-35 terminals No. 13 and 26, or PCM connector C-40 terminals No. 42 and 48. If each resistance is less than one ohm, go to next step. If either resistance is one ohm or more, repair wiring between ground and ECM/PCM. Grounds are located in engine compartment near battery and near ECM/PCM.
  8. Install MFI relay. On 2.4L M/T vehicles, disconnect ECM 16-pin connector C-36. On all vehicles, connect jumper wire between ground and ECM connector C-36 terminal No. 38, or PCM connector C-40 terminal No. 49. MFI relay should audibly click. Also, measure voltage between ground and ECM connector C-35 terminals No. 12 and 25, or PCM connector C-40 terminals No. 41 and 47. If battery voltage exists at each terminal, go to next step. If battery voltage does not exist at either terminal, repair appropriate wire between MFI relay and ECM/PCM.
  9. Check ECM connectors C-35, C-36 and C-38, or PCM connectors C-40 and C-41. If problem exists, repair appropriate connector. If problem does not exist, replace ECM/PCM.
scientia non olet · About LEMON Manuals