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Home >> Mazda >> 2002 >> MX-5 Miata Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0123: Throttle Position Sensor Circuit High Input >> Diagnostic Procedure

Diagnostic Procedure

  1. Turn ignition off. Connect New Generation Star (NGS) tester or equivalent to OBD-II Data Link Connector-2 (DLC-2). See Figure. Turn ignition on. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check for service bulletins and/or other line of repair information related to this DTC. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step  8. If repair information is not available, go to next step.
  2. Turn ignition off. Verify TP sensor harness connector is properly and securely connected. If connector is okay, go to next step. If connector is faulty, reconnect TP sensor connector tight and securely. After repair, go to step  8.
  3. Turn ignition off. Disconnect TP sensor 3-pin harness connector. See Figure. Check TPsensor for poor connection due to damaged, pulled-out pins, corrosion, etc. If connector terminals are okay, go to next step. If connector terminals are found faulty, repair or replace as necessary and go to step  8.
  4. With TP sensor harness connector disconnected, measure TP sensor circuits resistance as follow:
    • Between TP sensor harness connector terminals "A" and "B" (component side). Resistance should be 2.5-5.0 k/ohms.
    • Between TP sensor harness connector terminals "B" and "C" (component side). Resistance should be 0.2-1.1 k/ohms.

    If resistances are as specified, go to next step. If any resistance is not as specified, replace TP sensor. For circuit identification, see MIATA in WIRING DIAGRAMS article. After repair, go to step  8.

  5. With TP sensor harness connector disconnected, check continuity between ground and TP sensor harness connector terminal "B" (Black/Red wire). If continuity is found, go to step  7. If continuity is not found, go to next step.
  6. Leave TP sensor harness connector disconnected and disconnect PCM 31-pin harness connector. See Figure. Check PCM harness connector terminal "4L", "4V" and "4O" for poor connection due to damaged, pulled-out pins, corrosion, etc. If connector terminals are okay, go to next step. If connector terminals are found faulty, repair or replace as necessary and go to step  8
  7. With TP sensor and PCM harness connector disconnected, check continuity between TP sensor harness connector terminals "A" (Light Green/Red wire) and "C" (Green/Black wire). If continuity is not found, go to next step. If continuity is found, repair short between harness circuits (Light Green/Red and Green/Black wire). After repair, go to next step.
  8. Return vehicle to original condition. Using NGS tester or equivalent, clear DTCs from PCM memory. Start engine and let it idle until it reaches normal operation temperature. Monitor for pending DTCs. If same DTC P0123 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. If any other DTC is present, follow appropriate DTC diagnostic procedure.
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