2004 Mazda MX-5 Miata Base, AutomaticFACTORY OEM SERVICE PROCEDURE

VREF Terminal Circuit Inspection

  1. Turn the ignition switch to ON.
  2. Measure the voltage between the TP sensor connector (vehicle side) terminal A and body GND using a voltmeter.
    1. Measurement voltage is 0 V.
      1. Turn the ignition switch to LOCK.
      2. Disconnect the TP sensor connector, EGR boost sensor (BP), and BARO/MAP sensor (BP WITH TC) connector (to which Vref is applied).
      3. Verify there is no continuity between the TP sensor connector (vehicle side) terminal A and body GND using an ohmmeter.
        • If there is continuity, repair the related harness for short to circuit.
        Fig 1: Identifying TP Sensor Connector Terminals
        G00989683Courtesy of MAZDA MOTORS CORP.
      4. Inspect for continuity between the PCM connector (vehicle side) terminal 4L and each sensor connector (vehicle side) terminals to which Vref is applied using an ohmmeter.
        Fig 2: Identifying EGR Boost [BP], BARO/MAP [BP With TC] & TP Sensor Connectors
        G00989685Courtesy of MAZDA MOTORS CORP.
        • If there is continuity, repair the related harnesses.
        Fig 3: Checking Continuity Of PCM Connector (Vehicle Side) Terminal 4L & Each Sensor Connector (Vehicle Side) Terminals
        G00989684Courtesy of MAZDA MOTORS CORP.
    2. Measurement voltage is B+.
      1. Turn the ignition switch to LOCK.
      2. Disconnect the battery positive harness and battery negative harness.
      3. Verify there is no continuity between the TP sensor connector (vehicle side) terminal A and battery positive harness using an ohmmeter.
        • If there is continuity, repair the related harnesses for short to B+ circuit.
      4. Measurement voltage is approx. 5 V.
        • Vref terminal of PCM is okay.
      Fig 4: Identifying TP Sensor Connector
      G00989686Courtesy of MAZDA MOTORS CORP.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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