SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSMAZDA2008TRIBUTE S SPORT, 4WDREPAIR AND DIAGNOSISENGINE PERFORMANCEFUEL DELIVERYSYMPTOM TROUBLESHOOTING [ENGINE/FUEL - EXCEPT HYBRID]CATALYST EFFICIENCY MONITOR MALFUNCTION
2008 Mazda Tribute s Sport, 4WD

Catalyst Efficiency Monitor Malfunction

2008 Mazda Tribute s Sport, 4WDSECTION Catalyst Efficiency Monitor Malfunction
PROBLEM SYMPTOMS CHART - CATALYST EFFICIENCY MONITOR MALFUNCTION

DTC P0420, P0430 CATALYST EFFICIENCY MONITOR MALFUNCTION
DETECTION CONDITION
  • P0420 indicates Bank 1 catalyst system efficiency is below acceptable threshold.
  • P0430 indicates Bank 2 catalyst system efficiency is below acceptable threshold.
POSSIBLE CAUSES
  • Use of leaded fuel
  • Oil contamination
  • Cylinder misfiring
  • Damaged HO2S
  • Malfunctioning ECT/CHT sensor
  • Downstream HO2S wires incorrectly connected
  • Fuel pressure too high
  • Damaged exhaust system pipe
  • Damaged exhaust manifold
  • Damaged muffler/tailpipe assembly
  • Damaged catalytic converter
  • Retarded spark timing
NOTE:
  • Internal deterioration of a catalytic converter is usually caused by abnormal engine operation upstream of the catalyst. Events that can produce higher than normal temperatures in the catalyst are particularly suspect, such as misfiring.
  • Incorrect HO2S signal input (e.g., rich/lean signal when engine is operating under rich/lean conditions) can cause an abnormal temperature increase in the catalyst.
  • ECT/CHT sensor DTCs can indicate that the thermostat is not operating correctly or that the engine coolant level is not filled to specification, producing above normal operating temperatures.
HINT
G05463704
G05463705
INSPECTION CHART - CATALYST EFFICIENCY MONITOR MALFUNCTION

STEP INSPECTION ACTION
1 PCM QUICK TEST
NOTE:
  • If entering this test from the symptom troubleshooting, GO to the next step.
  • Was the PCM Quick Test carried out? 
 Yes If any other DTC is recorded, GO to appropriate DTC troubleshooting first.
If only DTC P0420 and/or P0430 are recorded, GO to the next step.
No Carry out the PCM Quick Test.
See PCM QUICK TEST  .
2 CHECK REAR HO2S WIRING AND PCM CONNECTIONS
NOTE:
  • If the electrical connections of the rear HO2S are interchanged/crossed, the Catalyst Efficiency Monitor Test will fail.
  • Inspect the wiring of the rear HO2S for correct routing and connection.
  • Disconnect the PCM, inspect for damaged or pushed out pins, corrosion and loose wires.
  • Are there any concerns with the H02S wiring or the PCM connection? 
 Yes REPAIR any wiring or connection concerns.
For PCM pin concerns, REPLACE the PCM.
See POWERTRAIN CONTROL MODULE (PCM) - 2.3L REMOVAL/INSTALLATION .
GO to step 9.
No No engine control system related to DTCs or symptoms.
GO to the next step.
3 CHECK FUEL PRESSURE
WARNING:
  • The fuel system will remain pressurized when the engine is not running. To prevent injury or fire, use caution when working on the fuel system.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.