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Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 61 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0140: Ho2S (Rear) Circuit - No Activity Detected >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda Protege5 and 2003 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
  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 next step.
  2. Verify Related Pending & Stored DTCs -  Turn ignition off, then start engine. Using scan tool, check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If no other DTCs except P0131 and P0132 are present, go to next step. If any other related DTCs are present, go to appropriate trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  3. Identify Trigger DTC For Freeze Frame Data -  Check if DTC P0140 is present in FREEZE FRAME DATA. If DTC P0140 is present, go to next step. If any other DTC is present that triggered freeze frame data, go to appropriate DTC trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  4. Verify Current Input Signal Status -  Start engine and warm up to operating temperature. Using scan tool, access O2S12 PID data. Race engine at least 10 times in neutral. O2S12 PID reading should be more than .55 volt at least once during engine racing. If PID reading is not as specified, go to next step. If PID reading is as specified, go to step  7.
  5. Inspect Installation Of HO2S (Rear) -  Check rear HO2S installation. If rear HO2S is not loose, go to next step. If rear HO2S is loose, retighten rear HO2S. After repair, go to step  9.
  6. Inspect Exhaust System For Gas Leakage -  Check for leaks in exhaust system upstream of rear HO2S. If problem is found, repair or replace faulty exhaust system components. After repair, go to step  9. If no leaks are found, check for open or short circuit to ground in Yellow/Blue wire between rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 35. See Figure and Figure . See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. Repair as necessary. After repair, go to step  9. If no problem is found, replace rear HO2S. After repair, go to step  9.
  7. Inspect Sealing Of Engine Coolant Passage -  Check cooling system for combustion gasses. Remove radiator cap. Bleed air from cooling system. Start engine and let idle. Check for small bubbles which make coolant white at filler neck. If combustion gasses are not present, go to next step. If combustion gasses are present, repair leak as necessary. After repair, go to step  9.
  8. Inspect Engine Compression -  Check engine compression. Engine compression should be a minimum of 119 psi (8.4 kg/cm2 ) at 300 RPM with a maximum variation of 28 psi (2 kg/cm2 ). If compression is as specified, go to next step. If compression is not as specified, repair as necessary. After repair, go to next step. If no problem is found, go to next step.
  9. Verify Trouble Shooting Of DTC P0140 Completed -  Reconnect all connectors. Turn ignition on, engine off. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Using scan tool, access ECT and RPM PIDs. Ensure ECT PID is more than 158°F (70°C). Increase engine speed to more than 1500 RPM (RPM PID reading) for more than 30 seconds. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0140 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 P0140 is not present, go to next step.
  10. 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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