Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Cadillac >> 1996 >> Seville SLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0420 - TWC System Low Efficiency >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Turn ignition on. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
  3. Check exhaust system for leaks, damage, loose or missing hardware. Repair as necessary. After repairs, go to step 5). If exhaust system is okay, go to next step.
  4. Ensure original 3-way catalytic converter is installed. Check converter for damage or tamper. Ensure oxygen sensors are properly installed and wiring and connections are okay. Repair or replace components as necessary. After repairs, go to next step. If components are okay, go to step 6).
  5. Using scan tool, select DTC INFO then DTC STATUS under DTC mode. Operate vehicle under which DTC was set. Observe scan tool display of DTC STATUS, looking for DTC to run or fail. If this DTC failed, go to next step. If this DTC did not fail, system is okay.
  6. Replace catalytic converter.
scientia non olet · About Mike's Workshop Manuals