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Home >> Mazda >> 2002 >> MX-5 Miata Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0122: Throttle Position Sensor Circuit Low 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  7. If repair information is not available, go to next step.
  2. Turn Ignition off. Disconnect TP sensor 3-pin harness connector. See Figure. Check continuity between TP sensor connector terminal "A" and "C" (component side). If continuity is found, check for poor connection at TP sensor terminal "C", repair or replace as necessary and go to next step. If continuity is not found, replace TP sensor. For circuit identification, see MIATA in WIRING DIAGRAMS article. After repair, go to step  7.
  3. Before proceeding with step 4), check retrieved DTCs. If DTCs P0107 and P0452 are also present with P0122, see REFERENCE VOLTAGE TEST  trouble shooting procedure. If no other DTCs is present, go to next step.
  4. With TP sensor harness connector disconnected, turn ignition on. Measure voltage between ground and TP sensor harness connector terminal "A" (Light Green/Red wire). Voltage should be 4.5-5.5 volts. If voltage is as specified, go to next step. If voltage is not as specified, repair open or short circuit (in Light Green/Red wire) between TP sensor and PCM. After repair, go to step  7.
  5. Turn ignition off. Leave TP sensor harness connector disconnected and disconnect PCM 31-pin harness connector. See Figure. Check continuity between TP sensor harness connector "C" and PCM harness connector terminal "4V" (Green /Black wire). If continuity is found, go to next step. If continuity is not found, repair open circuit (in Green /Black wire) between TP sensor and PCM. After repair, go to step  7.
  6. With TP sensor and PCM harness connector disconnected, measure continuity between ground and PCM harness connector terminal "4V" (Green/Black wire). If continuity is not found, go to next step. If continuity is found, repair short to ground circuit (in Green /Black wire) between TP sensor and PCM. After repair, go to next step.
  7. 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 P0122 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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