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Home >> Mazda >> 2003 >> Protege5 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0112: Intake Air Temperature Sensor Circuit - Low Input >> Diagnostic Procedure

Diagnostic Procedure

  1. Verify Related Repair Information Availability -  Turn ignition off. Connect scan tool to DLC-2. 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  6.
  2. Inspect IAT Sensor Terminals -  Turn ignition off. Disconnect IAT sensor 2-pin harness connector. Check for poor connection due to damaged, pulled-out terminals, corrosion, etc. If problem is not found, go to next step. If problem is found, repair as necessary. After repair, go to step  6.
  3. Classify IAT Sensor Malfunction Or Harness Malfunction -  Measure resistance between IAT sensor terminals. If resistance reading is 270-2900 ohms, go to next step. If resistance reading is not as specified, replace IAT sensor. After repair, go to step  6.
  4. Inspect IAT Signal Circuit For Short To Ground -  Disconnect PCM 104-pin harness connector. Check continuity between ground and IAT sensor harness connector terminal "B" (Blue/White wire). If continuity is not present, go to next step. If continuity is present, repair short circuit to ground in Blue/White wire between IAT sensor harness connector terminal "B" and PCM 104-pin harness connector terminal No. 39. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  6.
  5. Inspect IAT Circuits For Intermediate Short -  Check continuity between IAT sensor harness connector terminals. If continuity is not present, go to next step. If continuity is present, repair short in suspect harness between circuits. After repair, go to next step.
  6. Verify Trouble Shooting Of DTC P0112 Completed -  Reconnect all connectors. Turn ignition on, engine off. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0112 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. If same DTC P0112 is not present, 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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