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Home >> Infiniti >> 2001 >> Q45 Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420 Or P0430: Three-Way Catalyst Function >> Procedure
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DTC P0420 Or P0430: Three-Way Catalyst Function: Procedure

  1. Visually inspect exhaust system for damage or leaks. Start engine and run at idle. Check for exhaust leak prior to three-way catalyst. Check for intake air leak after MAF sensor. Repair or replace faulty components as required and retest system. If no problems exist, go to next step.
  2. Check ignition timing. See ON-VEHICLE ADJUSTMENTS article. Adjust, if necessary and retest system. If ignition timing is okay, go to next step.
  3. Turn ignition off. Remove ignition coils from rocker covers. Connect a known-good spark plug to coil and ground spark plug end. Crank engine and check for spark. If spark exists at all coils, go to next step. If spark does not exist at any coil, diagnose ignition system. See DTC P1320: IGNITION SIGNAL . Repair as necessary and retest system.
    4. CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  4. Turn engine off and turn ignition on. Measure voltage between ground and ECM terminals No. 1, 2, 3, 4, 5, 6, 7 and 14 by backprobing. See Figure. If battery voltage exists at each terminal, go to next step. If battery voltage does not exist at any terminal, repair fault in appropriate injector or circuit and retest system. See SYSTEM & COMPONENT TESTING article.
  5. Turn ignition off. Remove injector assembly, keeping fuel hose and all injectors connected. Disconnect CMP sensor harness connector. Turn ignition on. Verify fuel is not dripping from any injectors. Replace any injectors from which fuel is dripping. If all injectors are okay, go to next step.
  6. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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