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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 60 (Engine Controls [Self-Diagnostics 2.3L]) >> Diagnostic Tests >> DTC P0140: Rear Ho2S Circuit - No Activity Detected >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
  1. If FREEZE FRAME DATA has been recorded, go to next step. If FREEZE FRAME DATA has not been recorded, record FREEZE FRAME DATA. Go to next step.
  2. Verify Related Repair Information Availability -  Check for related Service Bulletins and/or on-line repair information availability. If any related repair information is available, perform repair or diagnosis according to available repair information. If vehicle is not repaired, go to next step. If related repair information is not available, go to next step.
    3. NOTE: If fuel monitor DTCs P0131 or P0132 are retrieved, ignore it until P0140 is fixed.
  3. Verify Related Pending Or Stored DTCs -  Turn ignition off, then on (engine off). Verify pending code or stored DTCs using WDS or equivalent. If other DTC is present, go to appropriate DTC trouble shooting procedures. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are present, go to next step.
  4. Identify Trigger DTC For FREEZE FRAME DATA -  If DTC P0140 is present on FREEZE FRAME DATA, go to next step. If any other DTC triggered FREEZE FRAME DATA, diagnose that DTC first. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  5. Verify Current Input Signal Status -  Warm up engine. Access O2S12 for P0140 or O2S22 for P0160 PID using WDS or equivalent. Verify PID while racing engine at least 10 times (in NEUTRAL (MTX) or PARK (ATX)). If PID reading is more than 0.55 volt at least once during engine racing, go to step  8. If PID reading is not more than 0.55 volt at least once during engine racing, go to next step.
  6. Inspect Installation Of Rear HO2S -  Check if rear HO2S is loosely installed. If rear HO2S is installed securely, go to next step. If rear HO2S is not installed securely, retighten rear HO2S. After repair, go to step  10.
  7. Inspect Gas Leakage From Exhaust System -  Visually check if any gas leakage is found between exhaust manifold and rear HO2S. If exhaust gas leak is not present, inspect harness for open or short to ground circuit between rear HO2S 4-pin harness connector terminal "A" and PCM 30-pin harness connector terminal "1Y" (White/Blue wire). See Figure. Repair or replace harness if necessary. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If all items are okay, replace faulty rear HO2S. After repair, go to step  10.
    8. WARNING: Removing radiator cap when radiator is hot is dangerous. Scalding coolant and steam may shoot out and cause serious injury. When removing radiator cap, wrap a thick cloth around cap and turn it slowly.
    NOTE: If there are any small bubbles which make engine coolant white at filler opening, air is getting in from poor sealing to head gasket or other areas between combustion chamber and engine coolant passage. Large bubbles are normal since they are remaining air coming out from engine coolant passage.
  8. Inspect Sealing Of Engine Coolant Passage -  Remove radiator cap. Perform procedure to bleed air from engine coolant, then run engine at idle. If there are any small bubbles which make engine coolant white at filler opening, repair or replace faulty parts. After repair, go to next step. If small bubbles are not present, go to next step.
  9. Inspect Engine Compression -  Inspect engine compression. Refer to MECHANICAL INSPECTION in BASIC DIAGNOSTIC PROCEDURES article. If engine compression is okay, go to next step. If engine compression is not okay, perform engine overhaul for repairs. After repair, go to next step.
  10. Verify Trouble Shooting Of DTC P0140 Is Completed -  Make sure to reconnect all disconnected connectors. Clear DTC from PCM memory using WDS or equivalent. Turn ignition off. Start engine and warm it up completely. If PENDING CODE of same DTC is not present, go to next step. If PENDING CODE of same DTC is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION article. After repair, go to next step.
  11. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If any DTCs are present, go to appropriate DTC inspection. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, trouble shooting is complete.
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