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Home >> Mazda >> 2003 >> MX-5 Miata Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0123: Throttle Position Sensor Circuit High Input >> Diagnostic Procedure
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Diagnostic Procedure

  1. Verify Related Repair Information Availability -  Turn ignition off. Connect scan tool to DLC-2. See Figure. Turn ignition on, engine off. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step  8.
  2. Check TP Sensor Connector -  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 secure. After repair, go to step  8.
  3. Inspect TP Sensor Connector For Poor Connection -  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. Check TP Sensor Resistance -  Measure resistance between following TP sensor terminals:
    • Terminals "A" and "B". Resistance reading should be 2500-5000 ohms.
    • Terminals "B" and "C". Resistance reading should be 200-1100 ohms.

    If resistances readings are as specified, go to next step. If any resistance readings are not as specified, replace TP sensor. After repair, go to step  8.

  5. Verify TP Sensor GND Circuit For Open At TP Sensor Connector -  Check continuity between ground and TP sensor 3-pin harness connector terminal "B" (Black/Red wire). If continuity is not present, go to next step. If continuity is present, go to step  7.
  6. Check PCM Connector -  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. After repair, go to step  8
  7. Verify TP Signal Circuit For Short To Constant Voltage Circuit -  Check continuity between TP sensor 3-pin harness connector terminals "A" (Light Green/Red wire) and "C" (Green/Black wire). If continuity is not present, go to next step. If continuity is present, repair short between TP sensor circuits (Light Green/Red and Green/Black wires). After repair, go to next step.
  8. Verify Troubleshooting Of DTC P0123 Completed -  Return vehicle to original condition. Using scan tool, clear DTCs from PCM memory. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and let idle until normal operating temperature is reached. Monitor for pending DTCs. If same DTC is not present, go to next step. 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. After repair, 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, follow appropriate DTC diagnostic procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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