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Cat Coverter or O2 sensor

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Old Jan 9, 2006 | 11:44 AM
  #1  
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Question Cat Coverter or O2 sensor

Have a 99 Ford F-150, 5.4L. Engine check light came on. Went do dealer and was told codes revealed bad Cat Coverter and recommended both coverters and all 02 sensors be replaced; however they advised to send it to someone else, because Ford would charge too much for repair.
Went to exhaust shop and they tested air flow. No problem. They said Cat Coverters were good. Must be O2.
Called Ford back and they said no, it is converters but both converters and all 02s need to be replaced to clear check engine light.
Called another Ford dealer and they said they dont automatically replace 02s with converters.
Need help. I already have $80 in this for getting checked by ford. What should I do to save money?
Truck is running good, no problems. Is there a way to disconnect cpu from exhaust Converters, that way light goes off, and will come back on if a different problem exists.
 
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Old Jan 9, 2006 | 12:40 PM
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How many miles on your truck?

How did the exhaust shop know the cat was good? Just becuase its not restricting air flow doesn't mean its good. Cats don't last forever and when they fail they stop oxidizing/reducing the exhaust gasses. THis is what sets the codes. The O2 sensors can detect when the cat is working or not. If the signal from the front and rear sensors looks the same than your cat is not doing its job and codes will be set.

They are probably hesitant to put a new cat in and leave the old O2 sensors since the sensors will go bad eventually too. If your truck is high mileage than you may want to just replace the sensors as well. Theoretically you shouldn't have to but if you plan on keeping your truck for a while it may be a good idea. Your call.

As tempting as it is, don't disconnect your O2 sensors. You'll have poor fuel control, high emissions, possibly poor fuel economy, and your check engine light will stay on forever.
 
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Old Jan 10, 2006 | 06:24 AM
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Originally Posted by greentrooper
Have a 99 Ford F-150, 5.4L. Engine check light came on. Went do dealer and was told codes revealed bad Cat Coverter and recommended both coverters and all 02 sensors be replaced; however they advised to send it to someone else, because Ford would charge too much for repair.
Went to exhaust shop and they tested air flow. No problem. They said Cat Coverters were good. Must be O2.
Called Ford back and they said no, it is converters but both converters and all 02s need to be replaced to clear check engine light.
Called another Ford dealer and they said they dont automatically replace 02s with converters.
Need help. I already have $80 in this for getting checked by ford. What should I do to save money?
Truck is running good, no problems. Is there a way to disconnect cpu from exhaust Converters, that way light goes off, and will come back on if a different problem exists.
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Old Jan 10, 2006 | 06:35 AM
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Did they tell you the dose numbers?? If it's something like Catalytic Inefficiency then your converter is not doing its job and needs to be replaced. They try and sell you O2 sensors to try and cover their butts and just incase they don't come out of the pipe nicely. I toatally agree with above statemant tho... with a lot of miles, you probably should.
 
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Old Jan 10, 2006 | 08:20 AM
  #5  
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On a 99 your cats should be fine unless your mileage is extreme. I would replace the O2 sensors and reset the check engine light. the O2 sensors usually give out before the cats. You cant drive the car without the O2 sensors cause all air/fuel ratio is determined from those sensors. If you have been driving the vehicle a long time with the sensors bad you can clog the cats with deposits.
 
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Old Jan 10, 2006 | 09:16 AM
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Question thanks and another question

Thanks for the info.

After replacing 02s how do you reset light?

Where is best place to order 02s and converters online?

Thanks again
 
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Old Jan 10, 2006 | 09:16 AM
  #7  
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oh i forgot

truck has 90,000
 
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Old Jan 10, 2006 | 09:54 AM
  #8  
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Based on my last Ford vehicle and others that have owned them, I would bet it's only the O2 sensors! Seems like 85 to 100K miles is the magic number for Ford O2 sensors to fail! If you drop the codes it will tell you which one is failing. Get the code from the dealer! I will also say after replacing the one pointed out by the code the others will soon follow behind!
You can reset the light 2 ways, either with a code reader you can get from your auto store or by disconnecting the battery. Be aware that by disconnecting the battery your PCM will have to relearn your driving and engine characteristics. So for the first hundred miles or so you may notice a change in idle, and or performance up until it relearns.
 

Last edited by KevinM; Jan 10, 2006 at 09:58 AM.
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Old Jan 10, 2006 | 10:06 AM
  #9  
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If you find out exactly what the codes are:

If only the cat efficiency codes - than most likely your cat is bad.
If only the O2 sensor codes - than your sensors are bad.
If O2 sensor codes & Cat efficiency codes - than it MAY only be your sensors.
 
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