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Home >> Mazda >> 2003 >> MPV ES >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC U0073: Can Bus Off >> Diagnostic Procedures
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Diagnostic Procedures

  1. Record freeze frame data. Check for service bulletins and on-line information. Repair as necessary. After repair, go to next step.
  2. Inspect Poor Connection Of TCM Connector -  Turn ignition off. Disconnect both TCM 24-pin harness connectors. 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  7.
  3. Check CAN Communication Line For Short To Ground -  Check for continuity between ground and TCM 24-pin harness connector terminal No. 2M (Yellow/Red wire). See Fig 1. If continuity is not present, go to next step. If continuity is present, repair short to ground in Yellow/Red wire between TCM 24-pin harness connector terminal No. 2M and PCM 104-pin harness connector terminal No. 50. See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. After repair, go to step  7.
    Fig 1: Identifying TCM 24-Pin Harness Connectors & Terminals
    G00159016Courtesy of MAZDA MOTORS CORP.
  4. Check CAN Communication Line For Short To Power -  Measure voltage between ground and TCM 24-pin harness connector terminal No. 2J (Red/Black wire). If battery voltage is not present, go to next step. If battery voltage is present, repair short to power in Red/Black wire between PCM 104-pin harness connector terminal No. 34 and TCM 24-pin harness connector terminal No. 2J. After repair, go to step  7.
  5. Inspect Poor Connection Of PCM Connector -  Turn ignition off. 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  7.
  6. Check CAN Communication Lines For Short Each Other -  Check continuity between PCM 104-pin harness connector terminals No. 49 (Red/Black wire) and No. 50 (Yellow/Red wire). If continuity is not present, go to next step. If continuity is present, repair short circuit between Red/Black and Yellow/Red wires between PCM 104-pin harness connecor and apropriate TCM 24-pin harness connector. After repair, go to next step.
  7. Verify DTC U0073 Detected Again -  Using scan tool, clear DTC. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Turn ignition off. Start engine. If DTC U0073 is present, replace PCM. After repair, go to next step. If DTC U0073 is not present, go to next step.
  8. 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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