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CODES P0421 and P0171
- Thread starter msp_rad
- Start date
fourthmeal
Banned
P0421 Warmup 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
Vehicle driven at a speed of 17-74 mph at 1500-3000 rpm with the calculated engine load from 15-48% for 2-3 minutes, and the PCM detected the inversion ratio of the rear HO2S was close to the inversion ratio of the front HO2S during the Catalyst Monitor test.
This code sets in 2 Trip(s).
P0171 Adaptive Fuel Trim Too Lean (Bank 1)
* 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
Engine running in closed loop at cruise speed for 2 minutes, and the PCM detected the A/F ratio remained leaner than the fuel correction limit in memory for 10 seconds during the Fuel System Monitor test.
This code sets in 2 Trip(s).
Hope this helps.
* 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
Vehicle driven at a speed of 17-74 mph at 1500-3000 rpm with the calculated engine load from 15-48% for 2-3 minutes, and the PCM detected the inversion ratio of the rear HO2S was close to the inversion ratio of the front HO2S during the Catalyst Monitor test.
This code sets in 2 Trip(s).
P0171 Adaptive Fuel Trim Too Lean (Bank 1)
* 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
Engine running in closed loop at cruise speed for 2 minutes, and the PCM detected the A/F ratio remained leaner than the fuel correction limit in memory for 10 seconds during the Fuel System Monitor test.
This code sets in 2 Trip(s).
Hope this helps.
fourthmeal
Banned
Check out that PCV system bud!
Check out that PCV system bud!
I just replaced my pcv with a millenia pcv about 2 months ago. Has been working good to my knowledge. Is there something else I should check?
OBDII codes P0421 and P0171
fourthmeal,
Your Mazda Manual must have been printed later than my July 2001 manual. My manual reads for P0421:
* WU-TWC deterioration or malfunction [WU-TWC = Warm Up - Three Way Catalyst]
*Exhaust gas leakage
*Looseness of HO2S (front)
*Looseness of HO2S (rear)
*HO2S (front) malfunction
P0171 reads:
*Misfire
*HO2S (front) deterioration
*HO2S (front) heater malfunction
*PRC solenoid valve malfunction
*Pressure regulator malfunction
*Fuel pump malfunction
*Fuel filter clogged or restricted
*Fuel leakage on fuel line from delivery pipe and fuel pump [sic]
*Fuel return hose clogged
*Leakage from exhaust system
*Purge solenoid valve malfunction
*Purge solenoid hoses improper connection
*Insufficient compression
Notice that fuel injectors are not mentioned at all in the possible problems.
I have these codes popping up on my OBDII tester. I am beginning to think that the injectors may be the problem. I have 160,000 miles on my stock 2.0 (replacing those items that should be replaced at the correct intervals, i.e. timing belt, etc.), but there is no statement in my service manual as to how long the fuel injectors will last without replacement. Is there a specific replacement interval?
As for other things that might contribute to this problem. The PCV valve appears to be good (it moves back and forth when shaken). I replaced the HO2S sensors when the first P0421 showed up. After clearing the code, it did not return for about 3 months. I have good compression (176 psi in 3 cylinders and 171 in the last one). I will replace the PCV valve but do not think that this will cure this problem. Any further thought on how to solve this?
fourthmeal,
Your Mazda Manual must have been printed later than my July 2001 manual. My manual reads for P0421:
* WU-TWC deterioration or malfunction [WU-TWC = Warm Up - Three Way Catalyst]
*Exhaust gas leakage
*Looseness of HO2S (front)
*Looseness of HO2S (rear)
*HO2S (front) malfunction
P0171 reads:
*Misfire
*HO2S (front) deterioration
*HO2S (front) heater malfunction
*PRC solenoid valve malfunction
*Pressure regulator malfunction
*Fuel pump malfunction
*Fuel filter clogged or restricted
*Fuel leakage on fuel line from delivery pipe and fuel pump [sic]
*Fuel return hose clogged
*Leakage from exhaust system
*Purge solenoid valve malfunction
*Purge solenoid hoses improper connection
*Insufficient compression
Notice that fuel injectors are not mentioned at all in the possible problems.
I have these codes popping up on my OBDII tester. I am beginning to think that the injectors may be the problem. I have 160,000 miles on my stock 2.0 (replacing those items that should be replaced at the correct intervals, i.e. timing belt, etc.), but there is no statement in my service manual as to how long the fuel injectors will last without replacement. Is there a specific replacement interval?
As for other things that might contribute to this problem. The PCV valve appears to be good (it moves back and forth when shaken). I replaced the HO2S sensors when the first P0421 showed up. After clearing the code, it did not return for about 3 months. I have good compression (176 psi in 3 cylinders and 171 in the last one). I will replace the PCV valve but do not think that this will cure this problem. Any further thought on how to solve this?
Sorry for adding another post, but I forgot a couple of items.
I have noticed that the P0171 pops up during idle and the idle is rough. Above idle the engine runs great. The engine does not act as though it is not getting the correct amount of fuel at higher speeds. It has not stalled, but the idle varies between 500 and 850. It does not hold steady at 750-800 where it should be. These symptoms indicate to me that the fuel filter is not clogged, the fuel pump is operating correctly, the fuel line is not pinched, nor is the return line clogged. There is no sound of a loose exhaust system connection. To my knowledge, there are no air leaks for the intake system and the catalyst should be good for another 140,000 miles. I hope this additional information will assist.
I have noticed that the P0171 pops up during idle and the idle is rough. Above idle the engine runs great. The engine does not act as though it is not getting the correct amount of fuel at higher speeds. It has not stalled, but the idle varies between 500 and 850. It does not hold steady at 750-800 where it should be. These symptoms indicate to me that the fuel filter is not clogged, the fuel pump is operating correctly, the fuel line is not pinched, nor is the return line clogged. There is no sound of a loose exhaust system connection. To my knowledge, there are no air leaks for the intake system and the catalyst should be good for another 140,000 miles. I hope this additional information will assist.
fourthmeal
Banned
Important information if I am asked to help:
I need the car's full description. A lot of programs simply use generic coding for P codes. The company I work for (Identifix) doesn't do this, instead it shows real world solutions with exact vehicles, to reduce diagnostic run-around. In order to provide any help whatsoever, I need to know the Year, Make (that one is easy for us!), Model, and any trim or engine differences.
Then, I can look up information for you.
I need the car's full description. A lot of programs simply use generic coding for P codes. The company I work for (Identifix) doesn't do this, instead it shows real world solutions with exact vehicles, to reduce diagnostic run-around. In order to provide any help whatsoever, I need to know the Year, Make (that one is easy for us!), Model, and any trim or engine differences.
Then, I can look up information for you.
- :
- Mazda Protege Titanium 03.5
I've never had the p0171 and the problem not been a vac leak.
