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Home >> Mitsubishi >> 2001 >> Galant LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Circuit Check >> Scan Tool Will Not Communicate >> No Communication With Powertrain Control Module (PCM)
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No Communication With Powertrain Control Module (PCM)

  1. Turn ignition off. Check PCM connector C-41 for loose, damaged or corroded terminals. See Figure. If problem exists, repair connector. If problem does not exist, go to next step.
  2. Check for open or short to ground in Gray/Red wire between OBD-II DLC terminal No. 1 and PCM connector C-41 terminal No. 84. See Figure and Figure . If problem exists, repair Gray/Red wire. If problem does not exist, go to next step.
  3. Check for open or short to ground in Red/White wire between OBD-II DLC terminal No. 7 and PCM connector C-41 terminal No. 85. If problem exists, repair Red/White wire. If problem does not exist, go to next step.
  4. Remove MFI relay from engine compartment relay box. Check MFI relay connector for loose, damaged or corroded terminals. If problem exists, repair connector. If problem does not exist, go to next step.
  5. 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, install MFI relay and go to next step.
  6. Measure voltage between ground and MFI relay connector terminals No. 3 and 4. See Figure. If battery voltage exists at both terminals, go to next step. If battery voltage does not exist at either or both terminals, repair Red/White wire between engine compartment relay box fuse No. 13 (20-amp) and MFI relay.
  7. Disconnect PCM connector C-41. Turn ignition on. Measure voltage between ground and PCM connector C-41 terminal No. 98 (Black/White wire). See Figure. If battery voltage exists, go to next step. If battery voltage does not exist, check Black/White wire between ignition switch and PCM. If problem exists, repair wiring between ignition switch and PCM. If problem does not exist, check ignition switch. Repair as necessary.
  8. Turn ignition off. Disconnect PCM 26-pin connector C-40. Measure voltage between ground and PCM connector C-40 terminal No. 66 (Red/Black wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair Red/Black wire between engine compartment relay box fuse No. 4 (10-amp) and PCM.
  9. Check for continuity between ground and PCM connector C-40 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 either terminal, repair wiring between ground and PCM.
  10. Measure voltage between ground and PCM connector C-40 terminal No. 49 (Light Blue wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair Light Blue wire between PCM and MFI relay.
  11. Connect jumper wire between ground and PCM connector C-40 terminal No. 49 (Light Blue wire). MFI relay should audibly click. Measure voltage between ground and PCM connector C-40 terminals No. 41 (Red wire) and No. 47 (Red wire). If battery voltage exists at each terminal, replace PCM. If battery voltage does not exist at either terminal, repair appropriate Red wire between MFI relay and PCM.
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