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DTC P1602: Immobilizer To Pcm Communication Error: Testing

NOTE: Record freeze frame data. Check for service bulletins and on-line information.
CAUTION: DO NOT crank engine before replacement PCM is programed to immobilizer system or PCM will be severely damaged. If test procedures require replacement of PCM on a vehicle equipped with immobilizer system and less than two valid keys are available, vehicle must be sent to authorized Mazda dealer to have replacement PCM programed.
  1. Using scan tool, clear all DTCs. Turn ignition off, then on. Recheck DTCs. If DTC P1624 is not present, go to next step. If DTC P1624 is present, go to step  9 .
  2. Turn ignition off. Disconnect 12-pin immobilizer unit harness connector, located under instrument panel to the right of steering column. Check immobilizer unit and immobilizer unit harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary. Go to step  18 .
  3. Check continuity between unit harness connector terminal "B" (Black/Orange wire) and ground. If continuity is present, go to next step. If continuity is not present, repair open in wiring between immobilizer unit harness connector terminal "B" (Black/Orange wire) and ground terminal (Black wire). See WIRING DIAGRAMS article. Go to step  18 .
  4. Disconnect 3-pin immobilizer coil connector, located next steering column by ignition switch. Check immobilizer coil and immobilizer harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary. Go to step  18 .
  5. Check continuity between immobilizer coil connector terminal "A" and ground. If continuity is not present, go to next step. If continuity is present, replace immobilizer coil. Go to step  18 .
  6. Reconnect immobilizer coil connector. Check continuity between immobilizer unit harness connector terminal "F" (Blue/Yellow wire) and ground. If continuity is not present, go to next step. If continuity is present, repair short to ground in Blue/Yellow wire between immobilizer coil harness connector terminal "A" and immobilizer unit harness connector terminal "F". Go to step  18 .
  7. Disconnect PCM harness connector. PCM is mounted to passenger floor, behind glove box. Check PCM and PCM harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary. Go to step  18 .
  8. Connect breakout box to PCM harness connector. Leave PCM disconnected. Check continuity between immobilizer unit harness connector terminal "A" (Blue/Black wire) and breakout box terminal No. 59. If continuity is present, go to step  18 . If continuity is not present, repair open in Blue/Black wire between immobilizer unit harness connector terminal "A" and PCM harness connector terminal No. 59. See Figure . Go to step  18 .
  9. If DTC P1602 is present, go to next step. If DTC P1602 is not present, go to step  13 .
  10. Disconnect 3-pin immobilizer coil connector, located inside steering column covers to right of steering column. Check immobilizer coil connector and immobilizer coil harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary. Go to step  18 .
  11. Check continuity between immobilizer coil connector terminals. If continuity is present, go to next step. If continuity is not present, replace immobilizer coil. Go to step  18 .
  12. Reconnect coil connector. Check continuity between immobilizer unit harness connector terminals "F" (Blue/Yellow wire) and "D" (Blue/White wire). If continuity is present, go to step  18 . If continuity is not present, repair open in wiring between immobilizer unit harness connector and immobilizer coil harness connector. See WIRING DIAGRAMS article. Go to step  18 .
  13. Check for immobilizer DTCs. If immobilizer DTC 03 is not present, go to next step. If immobilizer DTC 03 is present, key is missing transponder. Use another registered key. See DIAGNOSTIC TESTING (IMMOBILIZER SYSTEM) in SECURITY & LOCKS article in ACCESSORIES & EQUIPMENT. Go to next step.
  14. If immobilizer DTC 01 is not present, go to next step. If immobilizer DTC 01 is present, key is not registered. Reprogram key or use another registered key. See DIAGNOSTIC TESTING (IMMOBILIZER SYSTEM) in SECURITY & LOCKS article in ACCESSORIES & EQUIPMENT. Go to next step.
  15. Turn ignition off. Disconnect 12-pin immobilizer unit harness connector, located under instrument panel to right of steering column. Check immobilizer unit and immobilizer unit harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary and go to next step.
  16. Turn ignition on. Check voltage between immobilizer unit harness connector terminal "J" (Blue/Red wire) and ground. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, repair open in Blue/Red wire between immobilizer unit harness connector and No. 11 ROOM fuse terminal located in fuse block behind driver's kick panel. Go to step  18 .
  17. Check continuity between immobilizer unit harness connector terminal "A" (Blue/Black wire) and ground. If continuity is not present, go to next step. If continuity is present, repair short to ground in Blue/Black wire between immobilizer unit harness connector terminal "A" and PCM harness connector terminal No. 59. See Figure . Go to next step.
  18. Reconnect all components. Using scan tool, clear all DTCs. Turn ignition off. Start engine. Recheck DTCs. If same DTC is pending, replace PCM and go to next step. If same DTC is not pending, go to next step.
  19. Perform after repair procedure. See AFTER REPAIR PROCEDURE  . If DTC is not present, testing is complete. If any DTC is present, go to appropriate test for diagnosis and repair.
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