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Home › Mazda › 2002 › MPV ES › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P0140 Or DTC P0160 › Diagnostic Procedures

Diagnostic Procedures

  1. Record freeze frame data. Check for service bulletins and on-line information. Repair as necessary. After repair, go to next step.
    NOTE: During next procedure, if fuel monitor DTC P0131, P0132, P0151 or P0152 is retrieved, ignore it until P0140 or P0160 is fixed.
  2. Verify Related Pending & Stored DTCs -  Turn ignition on, engine off. Verify stored DTCs. If no other DTCs are present, go to next step. If any other DTCs are present, repair first.
  3. Identify Trigger DTC For FREEZE FRAME DATA -  Verify if DTC P0140 or P0160 are present in FREEZE FRAME DATA. If DTC is present, go to next step. If DTC P0140 or P0160 is not present in FREEZE FRAME DATA, go to appropriate DTC trouble shooting. Refer to DIAGNOSTIC TROUBLE CODE IDENTIFICATION .
  4. Verify Current Input Signal Status -  Start engine. Warm engine to operating temperature. Using scan tool, access O2S12 (P0140) or O2S22 (P0160). Depress accelerator pedal to WOT and release to race engine. Repeat at least 10 times in park or neutral. If PID reading is more than .55 volt at least once while racing engine, go to step  7. If PID reading is not as specified, go to next step.
  5. Inspect Installation Of HO2S (Rear) -  Check rear HO2S installation. If rear HO2S is loose, tighten rear HO2S and go to step  9. If rear HO2S is tight, go to step  9.
  6. Inspect Gas Leakage From Exhaust System -  Visually inspect for exhaust leakage between exhaust pipe and rear HO2S. If leak is found, replace faulty exhaust system part as necessary. If no leaks are found, check for open or short in circuit between:
    • Right rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 35 (Green wire). See Figure and Figure .
    • Left rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 61 (Blue/White wire).

    See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. If problem is found, repair as necessary. If no problem is found, replace suspect rear HO2S. After repair, go to step  9.

    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 and turn it slowly.
    NOTE: Large bubbles are normal since they are remaining air coming out from engine coolant passage.
  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 or replace faulty parts as necessary. After repair, go to step  9.
  8. Inspect Engine Compression -  Check engine compression. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES article. If compression is okay, go to next step. If compression is low, overhaul engine. Refer to appropriate MECHANICAL article in ENGINES. After repair, go to next step.
  9. Verify Trouble Shooting Of DTC P0140 Or P0160 Completed -  Reconnect all components. Turn ignition on, engine off. Using scan tool, clear DTC. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Ensure ECT PID is more than 158°F (70°C). Increase engine speed to more than 1500 RPM for more than 95 seconds. Recheck DTCs. If DTC P0140 or P0160 is present, replace PCM. After repair, go to next step. If DTC P0140 or P0160 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, go to applicable test and repair.
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