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Home >> Mazda >> 2003 >> MX-5 Miata Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0122: Throttle Position Sensor Circuit Low 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. 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  6.
  2. Check TP Sensor Circuit For Open Circuit -  Turn ignition off. Disconnect TP sensor 3-pin harness connector. See Figure. Check continuity between TP sensor connector terminals "A" and "C". If continuity is present, check for poor connection at TP sensor terminal "C", repair or replace as necessary. After repair, go to next step. If continuity is not present, replace TP sensor. After repair, go to step  6.
    NOTE: Before proceeding with next step, check retrieved DTCs. If DTCs P0107 and P0452 are also present with P0122, see REFERENCE VOLTAGE TEST  Troubleshooting procedure.
  3. Check Power Supply Circuit Voltage At TP Sensor Connector -  Turn ignition on, engine off. Measure voltage between ground and TP sensor 3-pin harness connector terminal "A" (Light Green/Red wire). Voltage reading should be 4.5-5.5 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, repair open or short circuit in Light Green/Red wire between TP sensor 3-pin harness connector terminal "A" and PCM 31-pin harness connector terminal "4L". See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  6.
  4. Verify TP Signal Circuit For Open -  Turn ignition off. Disconnect PCM 31-pin harness connector. See Figure. Check continuity between TP sensor 3-pin harness connector terminal "C" and PCM 31-pin harness connector terminal "4V" (Green /Black wire). If continuity is present, go to next step. If continuity is not present, repair open circuit in Green /Black wire between TP sensor 3-pin harness connector and PCM 31-pin harness connector terminal "4V". After repair, go to step  6.
  5. Verify TP Signal Circuit For Short To GND -  Check continuity between ground and PCM 31-pin harness connector terminal "4V" (Green/Black wire). If continuity is not present, go to next step. If continuity is present, repair short circuit to ground in Green /Black wire between TP sensor 3-pin harness connector terminal "C" and PCM 31-pin harness connector terminal "4V". After repair, go to next step.
  6. Verify Troubleshooting Of DTC P0122 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. Depress and release accelerator pedal several times. Monitor for pending DTCs. If same DTC is not present, go to next step. If same DTC P0122 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.
  7. 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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