Engine Code P0421 - O2 Sensor Question

[jgrant59]

I have a 2001 Protege Es 2.0 with about 100k Km (60K miles).

I recently received a P0421 Engine code, cross referenced as "Warm Up Catalyse Efficiency Below Threshold (Bank 1)"

As this probably relates to O2 Sensors or Catalytic Converter, I analysed the O2 sensor voltages on three separate samples.

The Bank 1 forward sensor voltage varies between about .1v and .8v, which I believe is pretty normal.

My question relates to Bank 1 sensor 2. The output voltage is steady at .45 volts for about 2 minutes then starts to vary between .15v and .8v.

Is this a normal output for the sensor?

Any assistance would certainly be appreciated.

[apocman]

that could be an exhaust leak between the two o2 sensors

[jgrant59]

Good Idea, I will check and see if I can see / hear any leaks.

I am also running a bottle of fuel system cleaner through, do you think this would effect the results of the O2 sensor data, or have caused the CIL??

Any thoughts.....

John

[apocman]

could have been, I know SeaFoam is o2 safe, but other products can cuase the o2 to freak out...

try this get a can of seafoam and then get a peice of vacuum hose and a two-way vacuum line connector pull the pvc vavle off of the hose its connected to on top of the vavle cover and then start the car and have a friend rev it while you slowely stick the vac line into the can it will smoke like crazy for a few minutes out of the exhuast and if there are any exhuast or vac leaks it will come out of those places as well.. its an easy way to check for leaks and clean your cars insides at the same time...



Good Idea, I will check and see if I can see / hear any leaks.

I am also running a bottle of fuel system cleaner through, do you think this would effect the results of the O2 sensor data, or have caused the CIL??

Any thoughts.....

John

[Diehonda]

could have been, I know SeaFoam is o2 safe, but other products can cuase the o2 to freak out...

try this get a can of seafoam and then get a peice of vacuum hose and a two-way vacuum line connector pull the pvc vavle off of the hose its connected to on top of the vavle cover and then start the car and have a friend rev it while you slowely stick the vac line into the can it will smoke like crazy for a few minutes out of the exhuast and if there are any exhuast or vac leaks it will come out of those places as well.. its an easy way to check for leaks and clean your cars insides at the same time...


Let me add one more detail, let the vac line suck it slow enoughto not kill the engine(your buddy may have to hold the throttle down a bit) and then immediately turn the engine off and wait 15 minutes. Then start it up and take a drive, that will clean the TB and intake parts. But if you are looking for an exhaust leak, you will want your buddy to push the throttle down a bit while you inspect. The smoke will be very light gray to white. If you have a lot of build up the area around you car will turn totally 007 and make it difficult to see the leak or anywhere else for that matter.

[jgrant59]

I have a 2001 Protege Es 2.0 with about 100k Km (60K miles).

I recently received a P0421 Engine code, cross referenced as "Warm Up Catalyse Efficiency Below Threshold (Bank 1)"

As this probably relates to O2 Sensors or Catalytic Converter, I analysed the O2 sensor voltages on three separate samples.

The Bank 1 forward sensor voltage varies between about .1v and .8v, which I believe is pretty normal.

My question relates to Bank 1 sensor 2. The output voltage is steady at .45 volts for about 2 minutes then starts to vary between .15v and .8v.

Is this a normal output for the sensor?

Any assistance would certainly be appreciated.


Based on the output from the CarChip downstream O2 Sensor, I took the car into my local Mazda dealer. They verified that the Catalytic Convertor was infact "BAD". As the extended emissions warranty expires at 126K km, I was able to get it replaced.... free of charge!!

Retesting with the CarChip now shows the proper waveform on the output of the O2 Sensor.

I am really pleased with my purchase of the Davisnet Carchip and recommend it to anyone. http://www.davisnet.com/drive/products/carchip_products.asp

Thanks to all who helped me with this one.