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Home >> Mazda >> 2003 >> MPV ES >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0703: Brake Switch - Input Malfunction >> 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 Brake Switch Signal Circuit For Short To Power -  Measure voltage between ground and brake pedal switch harness connector terminal "B" (Green/Yellow wire). See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. If battery voltage is not present, go to next step. If battery voltage is present, repair short to voltage in Green/Yellow wire between brake switch harness connector terminal "B" and PCM 104-pin harness connector terminal No. 92. After repair, go to step  8.
  3. Inspect Brake Switch Connector For Poor Connection -  Turn ignition off. Disconnect brake switch 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  8.
  4. Inspect Brake Switch Power Circuit For Open Circuit -  Measure voltage between ground and brake switch harness connector terminal "A" (Green wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Green wire between brake switch harness connector terminal "A" and positive battery terminal. After repair, go to step  8.
  5. Inspect PCM Connector For Poor Connection -  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  8.
  6. Inspect Brake Switch Signal Circuit For Open Circuit -  Connect 104-pin Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Reconnect brake light switch harness connector. Turn ignition on, engine off. Depress brake pedal and measure voltage between ground and breakout box terminal No. 92. If battery voltage is present, go to next step. If battery voltage is not present, repair open in Green/Yellow wire between brake light switch harness connector terminal "B" and PCM 104-pin harness connector terminal No. 92. After repair, go to step  8.
  7. Inspect Brake Switch -  Disconnect brake light switch harness connector. Check for continuity between brake light switch terminals. Continuity should be present only when brake pedal is depressed. If brake switch is okay, go to next step. If brake switch is faulty, replace brake switch. After repair, go to next step.
  8. Verify Trouble Shooting Of DTC P0703 Completed -  Reconnect all disconnected connectors. Using scan tool, clear DTC. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Drive vehicle at 18.6 MPH or more. Depress and release brake pedal more than 10 times while driving. Recheck DTCs. If DTC P0703 is present, replace PCM. After repair, go to next step. If DTC P0703 is not present, go to next step.
  9. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If no other DTCs are present, testing is complete. If any other DTC is present, go to applicable test and repair.
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