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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 connector, located under instrument panel to the left of steering column. Check unit and connector terminals. If no problem is found, go to next step. If any problem is found, repair as necessary. After repair, 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 on Black/Orange wire. After repair, go to step  18 .
  4. Disconnect 3-pin immobilizer coil connector, located next to immobilizer unit. Check coil and connector terminals. If no problem is found, go to next step. If any problem is found, repair as necessary. After repair, go to step  18 .
  5. Check continuity between coil terminal "A" and ground. If continuity is not present, go to next step. If continuity is present, replace coil. After repair, go to step  18 .
  6. Reconnect coil connector. Check continuity between 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 on Blue/Yellow wire. After repair, go to step  18 .
  7. Disconnect PCM connector. PCM is mounted to passenger floor, behind glove box. Check PCM and connector terminals. If no problem is found, go to next step. If any problem is found, repair as necessary. After repair, go to step  18 .
  8. Connect breakout box to PCM connector. Leave PCM disconnected. Check continuity between 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 on Blue/Black wire. After repair, 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 under instrument panel to the left of steering column. Check coil and connector terminals. If no problem is found, go to next step. If any problem is found, repair as necessary. After repair, go to step  18 .
  11. Check continuity between coil terminals. If continuity is present, go to next step. If continuity is not present, replace coil. After repair, go to step  18 .
  12. Reconnect coil connector. Check continuity between 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, replace coil. After repair, 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. After repair, 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. After repair, go to next step.
  15. Turn ignition off. Disconnect 12-pin immobilizer unit connector, located under instrument panel to the left of steering column. Check unit and connector terminals. If no problem is found, go to next step. If any problem is found, repair as necessary and go to next step.
  16. Turn ignition on. Check voltage between unit harness connector terminal "J" (Blue/Red wire) and ground. If battery voltage is present, go to next step. If battery voltage is not present, repair open on Blue/Red wire between immobilizer unit and ROOM fuse (No. 11) located in driver's kick panel. After repair, go to step  18 .
  17. Check continuity between 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 on Blue/Black wire between immobilizer unit and PCM. After repair, 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. See PROGRAMMING in SECURITY & LOCKS article in ACCESSORIES & EQUIPMENT. If same DTC is not pending, go to next step.
  19. Perform after repair procedure. See AFTER REPAIR PROCEDURE  . If no DTC is present, testing is complete. If any DTC is present, go to appropriate test for diagnosis and repair.
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