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Home >> Mazda >> 2001 >> MX-5 Miata Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0703: Brake Switch Input Circuit Malfunction >> Diagnosis & Repair Procedure
July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

Diagnosis & Repair Procedure

  1. Ensure FREEZE FRAME DATA has been recorded. Check for related service bulletins. Repair as necessary and go to next step.
  2. Using scan tool, access BRK SW PID data. Depress and release brake pedal several times. PID data should read on when pedal is depressed and off when pedal is released. If PID data is not as specified, go to next step. If PID data is as specified, problem is intermittent. See TROUBLE SHOOTING - NO CODES article.
  3. Release brake pedal. Using scan tool, access BRK SW PID data. If PID data is on with pedal released, go to next step. If PID data is not on with pedal released, go to step  6.
  4. Disconnect brake switch. Using scan tool, access BRK SW PID data. If PID data does not change to off, go to next step. If PID data changes to off, replace switch and go to step  12.
  5. Measure voltage between ground and brake switch harness connector terminal "B" (Green wire). If battery voltage is not present, go to step  12. If battery voltage is present, repair short to power in Green wire. See WIRING DIAGRAMS article. Go to step  12.
  6. Depress brake pedal. Using scan tool, access BRK SW PID data. If PID data is off with pedal depressed, go to next step. If PID data is on with brake pedal depressed, go to step  12.
  7. Disconnect brake switch. Check connector for loose or damaged terminals, poor contact or corrosion. Repair as necessary and go to step  12. If no problems are found, go to next step.
  8. Connect a jumper wire between brake switch harness connector terminals. Turn ignition on. Using scan tool, access BRK SW PID data. If PID data does not change to on, go to next step. If PID data changes to on, replace switch and go to step  12.
  9. Measure voltage between brake switch harness connector terminal "A" (White/Green wire) and ground. If battery voltage is present, go to next step. If battery voltage is not present, repair open in White/Green wire. See WIRING DIAGRAMS article. Go to step  12.
  10. Turn ignition off. Disconnect appropriate PCM connector. Check connector for loose or damaged terminals, poor contact or corrosion. Repair as necessary and go to step  12. If no problems are found, go to next step.
  11. Connect brake switch connector. Turn ignition on. Depress brake pedal. Measure voltage between ground and PCM harness connector terminal No. 4B (Green wire). See Figure. If battery voltage is present, go to next step. If battery voltage is not present, repair open in Green wire and go to next step.
  12. Reconnect all connectors. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Drive vehicle at 18.6 MPH or more. While driving, depress brake pedal 10 times or more. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0703 is present, replace PCM and go to next step. On vehicles equipped with immobilizer system, reprogram ignition key identification numbers. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. If DTC P0703 is not present, go to next step.
  13. Cycle ignition from off to on. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If any other DTC is present, go to appropriate test.
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