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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 112 (Engine Controls Self-Diagnostics - Pathfinder) >> Diagnostic Tests >> DTC P0420: Bank 1 Catalyst System Efficiency - Below Threshold Or P0430: Bank 2 Catalyst System Efficiency - Below Threshold >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
  1. Visually inspect exhaust system for damage. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, repeat appropriate DTC confirmation test.
  2. Start engine and let it idle. Check for exhaust leak before 3-way catalyst. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, repeat appropriate DTC confirmation test.
  3. Check for intake air leak after MAF sensor. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, repeat appropriate DTC confirmation test.
  4. Check ignition timing and target idle speed. See ON-VEHICLE ADJUSTMENTS article. If ignition timing and target idle speed are as specified, go to next step. If ignition timing and target idle speed are not as specified, perform appropriate THROTTLE POSITION SWITCH, IGNITION TIMING & IDLE SPEED under BASIC INSPECTION in ON-VEHICLE ADJUSTMENTS article.
  5. Turn ignition off, and then on. Backprobing at ECM, measure voltage between ground and ECM terminals No. 21, 22, 23, 40, 41 and 42. If battery voltage exists at each terminal, go to next step. If battery voltage does not exist at each terminal, test fuel injectors. Perform fuel injector testing procedure, see FUEL SYSTEM in SYSTEM & COMPONENT TESTING article.
  6. 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, repair ignition system. See IGNITION SYSTEM in SYSTEM & COMPONENT TESTING article.
  7. Turn ignition off. Remove injector assembly, keeping fuel hose and all injectors connected. See FUEL SYSTEM in REMOVAL & INSTALLATION - PATHFINDER article. Disconnect all ignition coil harness connectors. 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.
  8. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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