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Home >> Mitsubishi >> 2003 >> Montero Sport LS, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Testing Procedure >> 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-91 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 wire between OBD-II DLC terminal No. 1 (Green/Red wire) and PCM connector C-91 terminal No. 84 (Gray/Red wire). See Figure and Figure . If problem exists, repair Green/Red wire or Gray/Red wire. If problem does not exist, go to next step.
  3. Check for open or short to ground in wire between OBD-II DLC terminal No. 7 (Yellow/Orange wire) and PCM connector C-91 terminal No. 85 (Yellow wire). If problem exists, repair Yellow/Orange wire or Yellow wire. If problem does not exist, go to next step.
  4. Remove MFI relay. See Fig 1. 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 and 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 White/Black wire between MFI relay connector and fusible link No. 2 (20-amp).
  7. Disconnect PCM connector C-91. Check PCM connector C-91 for loose, damaged or corroded terminals. If problem exists, repair connector as necessary. If problem does not exist, go to next step.
  8. Turn ignition on. Measure voltage between ground and PCM connector C-91 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.
  9. Turn ignition off. Disconnect PCM 26-pin connector C-90. Measure voltage between ground and PCM connector C-90 terminal No. 66 (Black/Green wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair Black/Green wire, Red/Black wire, Red wire or White/Red wire between PCM and fusible link No. 6 (40-amp).
  10. Check for continuity between ground and PCM connector C-90 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.
  11. Measure voltage between ground and PCM connector C-90 terminal No. 49 (Blue/Green wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair Blue/Green wire between PCM and MFI relay.
  12. Connect jumper wire between ground and PCM connector C-90 terminal No. 49 (Blue/Green wire). MFI relay should audibly click. Measure voltage between ground and PCM connector C-90 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.
Fig 1: Locating MFI Relay, Fuel Pump Relay and 4WD Indicator ECU
G00023273Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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