Question about 2001 Mazda MPV
First Code PO421 warm up catalyst below threshold bank 1.
Second Code P1173 no DTC definition found.
Third Code PO174 system to lean bank 2.
Trouble Code: P0421
Catalyst Efficiency Below Normal (Bank 1)
Air leaks at the exhaust manifold or in the exhaust pipes
Catalytic converter is contaminated, damaged or has failed
Front HO2S and/or the rear HO2S is loose in the mounting hole
Front HO2S older (aged) than the rear HO2S (HO2S is lazy)
Front HO2S or rear HO2S is contaminated with fuel or moisture
Trouble Code: P1173
HO2S-21 (Bank 2 Sensor 1) Circuit Malfunction
Base engine mechanical fault affecting one or more cylinders
EVAP Purge valve stuck or the hoses to the valve are reversed
Fuel metering fault (fuel injector sticking open or leaking)
Fuel pressure too low or too high, fuel supply contaminated
HO2S element is contaminated or the HO2S heater has failed
PCV system has air leaks at the valve or related hoses
Trouble Code: P0174
Adaptive Fuel Trim Too Lean (Bank 2)
Vehicle driven low on fuel or until it ran out of fuel
One or more injectors restricted or pressure regulator has failed
Fuel delivery system supplying too much or too little fuel during cruise or idle periods (e.g., faulty fuel pump, or dirty fuel filter)
Air leaks after the MAF sensor, or air leaks in the PCV system
Air leaks at the EGR gasket, or at the EGR valve diaphragm
Exhaust leaks before or near where the front HO2S is mounted
HO2S is contaminated, deteriorated or it has failed
Fuel control sensor is out of calibration (i.e., ECT, IAT or MAP)
Base engine -mechanical- fault affecting one or more cylinders
Posted on May 18, 2009
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Posted on Jan 02, 2017
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hi,my friend, you can try,
Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
Inspect the downstream heated oxygen sensor (HO2), replace if necessary
Replace the catalytic converter
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