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Home >> Mazda >> 2003 >> MPV ES >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1602: Immobilizer Unit To Pcm Communication Error >> Diagnostic Procedures

Diagnostic Procedures

  1. Verify Related Repair Information Availability -  Check for service bulletins and on-line information. Repair as necessary. After repair, go to next step.
  2. Classify No DTC Detected Or Some DTC Detected -  Using scan tool, clear all DTCs. Turn ignition off, then on (engine off). Recheck DTCs. If DTC P1624 is not present, go to next step. If DTC P1624 is present, go to step  10.
  3. Inspect Poor Connection Of Immobilizer Unit Connector -  Turn ignition off. Disconnect immobilizer unit 12-pin harness connector, located under instrument panel to right of steering column. Check for damaged, loose or corroded terminals. If no problem is found, go to next step. If problem is present, repair terminal or connector as necessary. After repair, go to step  19.
    NOTE: Wire color changes between immobilizer unit and ground terminal at inline harness connector "X-05".
  4. Inspect Ground Circuit Of Immobilizer Unit For Open -  Check continuity between ground and immobilizer unit 12-pin harness connector terminal "C" (Black/Orange wire). See Fig 1. If continuity is present, go to next step. If continuity is not present, repair open circuit between immobilizer unit 12-pin harness connector terminal "C" (Black/Orange wire) and ground terminal (Black wire). See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. After repair, go to step  19.
    Fig 1: Identifying Immobilizer Unit 12-Pin Harness Connector Terminals
    G00143784Courtesy of MAZDA MOTORS CORP.
  5. Inspect Coil Terminal -  Disconnect 3-pin immobilizer coil connector, located inside steering column covers to right of steering column. Check for damaged, loose or corroded terminals. If no problem is found, go to next step. If problem is present, repair terminal or connector as necessary. After repair, go to step  19.
  6. Inspect Coil For Short Circuit -  Check continuity between ground and immobilizer coil 3-pin connector terminal "A". See Fig 2. If continuity is not present, go to next step. If continuity is present, replace immobilizer coil. After repair, go to step  19.
    Fig 2: Identifying Immobilizer Coil 3-Pin Harness Connector Terminals
    G00143783Courtesy of MAZDA MOTORS CORP.
  7. Inspect Coil Circuit For Short -  Reconnect immobilizer coil 3-pin harness connector. Check continuity between ground and immobilizer unit 12-pin harness connector terminal "F" (Blue/Yellow wire). If continuity is not present, go to next step. If continuity is present, repair short to ground in Blue/Yellow wire between immobilizer coil 3-pin harness connector terminal "A" and immobilizer unit 12-pin harness connector terminal "F". After repair, go to step  19.
  8. Inspect Poor Connection Of PCM Connector -  Disconnect PCM 104-pin harness connector. Check for damaged, loose or corroded terminals. If no problem is found, go to next step. If problem is present, repair terminal or connector as necessary. After repair, go to step  19.
  9. Inspect Communication Line For Open Circuit -  Connect 104-pin Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Check continuity between immobilizer unit 12-pin harness connector terminal "A" (Blue/Black wire) and breakout box terminal No. 59. If continuity is present, go to step  19. If continuity is not present, repair open in Blue/Black wire between immobilizer unit 12-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 59. See Figure and Fig 1 . After repair, go to step  19.
  10. Classify Malfunction By Another Detected DTC -  If DTC P1602 is present, go to step  14. If DTC P1602 is not present, go to next step.
  11. Inspect Poor Connection Of Coil Connector -  Disconnect immobilizer coil 3-pin harness connector, located inside steering column covers to right of steering column. Check for damaged, loose or corroded terminals. If no problem is found, go to next step. If problem is present, repair terminal or connector as necessary. After repair, go to step  19.
  12. Inspect Coil For Open -  Check continuity between immobilizer coil 3-pin connector terminals. If continuity is present, go to next step. If continuity is not present, replace immobilizer coil. After repair, go to step  19.
  13. Inspect Coil Circuit For Open -  Reconnect immobilizer coil 3-pin harness connector. With immobilizer unit 12-pin harness connector disconnected, check continuity between immobilizer unit 12-pin harness connector terminals "F" (Blue/Yellow wire) and "D" (Blue/White wire). See Fig 1. If continuity is present, go to step  19. If continuity is not present, repair open in wiring between immobilizer unit 12-pin harness connector and immobilizer coil 3-pin harness connector. See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. After repair, go to step  19.
  14. Classify Malfunction By Another Detected DTC - Check for immobilizer DTCs. If immobilizer DTC 03 (ID number is not input into immobilizer unit after cranking engine.) is not present, go to next step. If immobilizer DTC 03 is present, key has no transponder. Use another registered key. After repair, go to step  19.
  15. Classify Malfunction By Another Detected DTC -  If immobilizer DTC 01 (ID number unregistered in immobilizer unit is input after engine cranking.) is not present, go to next step. If immobilizer DTC 01 is present, key being used in ignition is not registered. Reprogram key or use another registered key. See appropriate IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. After repair, go to next step.
  16. Inspect Poor Connection Of Immobilizer Unit Connector -  Turn ignition off. Disconnect immobilizer unit 12-pin harness connector, located under instrument panel to right of steering column. Check for damaged, loose or corroded terminals. If no problem is found, go to next step. If problem is present, repair terminal or connector as necessary. After repair, go to next step.
  17. Inspect Immobilizer Unit Power Circuit For Open -  Turn ignition on, engine off. Check voltage between ground and immobilizer unit 12-pin harness connector terminal "J" (Blue/Red wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Blue/Red wire between immobilizer unit 12-pin harness connector terminal "J" and No. 11 ROOM fuse terminal located in joint box. Joint box is located under dash, behind kick panel. See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. After repair, go to step  19.
  18. Inspect Communication Line For Short Harness -  Check continuity between ground and immobilizer unit 12-pin harness connector terminal "A" (Blue/Black wire). If continuity is not present, go to next step. If continuity is present, repair short to ground in Blue/Black wire between immobilizer unit 12-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 59. See Figure and Fig 1 . After repair, go to next step.
  19. Verify Trouble Shooting Of DTC P1602 Completed -  Reconnect all components. Using scan tool, clear all DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Turn ignition off. Start engine. Recheck DTCs. If same DTC is present, replace PCM. Perform immobilizer system reprogram procedure (code word). See appropriate IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. After repair, go to next step. If same DTC is not present, go to next step.
  20. Verify After Repair Procedure -  Using scan tool, 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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