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2nd Gen Ram Tech 1994-2001 Rams: This section is for TECHNICAL discussions only, that involve the 1994 through 2001 Rams. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.

Do o2 sensor's ever go bad without CEL light coming on?

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Old 07-14-2014, 01:52 AM
501ram 501ram is offline
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Default Do o2 sensor's ever go bad without CEL light coming on?

Hi Everyone,

I have a 1995 Dodge Ram 1500 3.9 V6 (220,000 miles)

I've owned this truck for over 12 years and I have never once had the check engine light come on. My catalytic converter however has to be replaced every 3 - 4 years in order to pass emissions testing (something is burning it up, possibly running too rich). When I asked the shop putting in my catalytic converter, they said there are a few things to check but to probably start with my o2 sensor (these cats should last much much much longer than 4 years). I've never replaced my o2 sensor in the 12 years I've had the truck (there is only one o2 sensor on these trucks and it is found right before the cat).

I just replaced it to be safe, took like 20 minutes but I don't really feel any difference in the way the truck drives with a new one in.

I have four questions?

1) Is it possible my original o2 sensor failed without ever throwing a check engine light?

2) How long do O2 sensors usually last on Dodge Ram trucks?

3) Do 1995 Dodge Ram Trucks ever even have check engine lights come on?

4) Is it common to replace a bad o2 sensor with a new good one yet feel no difference in performance?

Thanks for any help.
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Old 07-14-2014, 07:58 AM
1997JollyGreenGiant 1997JollyGreenGiant is offline
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Is your truck using any oil? I'm wondering if your plenum is blown and you're leaking oil down into it, which is messing up your O2 sensors and your catalytic converter.
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Old 07-14-2014, 09:08 AM
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Ram Driver Ram Driver is offline
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If your truck has 220,000 miles on it with the original 02 sensor, then its bad. Its recommended that the 02 sensor be replaced every 60,000 - 70,000 miles, so your way past due. An 02 sensor can go bad in two ways, it can fail and throw a code, or with lots of miles on it, it gets lazy and can`t function as it should when it was new.


A bad 02 sensor will effect how your truck runs, and your gas mileage. It would be a good idea to replace your 02 sensor. Don`t use a Bosch 02 sensor in your truck, they don`t work well in our trucks. Use a Denso or NTK 02 sensor. I got my 02 sensors from rock auto for a good price.
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Old 07-14-2014, 09:17 AM
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Gary-L Gary-L is offline
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Quote:
Originally Posted by Ram Driver View Post
If your truck has 220,000 miles on it with the original 02 sensor, then its bad. Its recommended that the 02 sensor be replaced every 60,000 - 70,000 miles, so your way past due. An 02 sensor can go bad in two ways, it can fail and throw a code, or with lots of miles on it, it gets lazy and can`t function as it should when it was new.


A bad 02 sensor will effect how your truck runs, and your gas mileage. It would be a good idea to replace your 02 sensor. Don`t use a Bosch 02 sensor in your truck, they don`t work well in our trucks. Use a Denso or NTK 02 sensor. I got my 02 sensors from rock auto for a good price.
^^ THIS ^^

I will repeat myself for the umpteenth time, so here goes:

Back when I had my Second Gen I took it to a local exhaust guy I know for a new exhaust and catalytic converter after I had the engine rebuilt. The reason for replacing both are that the truck had zero power and the CEL would blink during vehicle operation. A pressure test on the catalytic converter showed that it was clogged.

The waiting area of the shop had a general diagram of a motor vehicle's emissions system that detailed each component's function and symptoms of failure. The chart noted that a catalytic converter will outlast the vehicle provided that the emissions system is properly maintained (barring manufacturing defects of the converter).

Items such as the O2 sensors will degrade in function over time even though an error code is not triggered. They key is that the O2 sensor is monitored through the PCM for voltage and ability to properly warm up. It is also covered with a special film and the exposed sensor should not be touched by human hands (think skin oils) as doing so can affect the sensor's performance. The manufacturers of the sensors print a replacement interval on the box of anywhere from 50-75K miles. Although some people will balk at the cost, it is saving the owner time and money in the long run considering the cost of fuel, oil, engine performance, and other mechanical wear and tear.


Here is an interesting read on O2 sensors: Oxygen Sensors Technical Information
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Last edited by Gary-L; 07-18-2014 at 11:38 AM..
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Old 07-14-2014, 09:17 AM
 
 
 
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catalytic converter, dodge ram 1500, o2 sensor, oxygen sensor, v6 3.9

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