I have a Check Engine Light. Auto Zone Scanner says O-2 sensor bank one sensor two (after the Cat.) high voltage.

A little history: I don't have a Cat. Conv. I have true duals with the flanges for the sensors welded into the pipes. One sensor in each pipe. It was explained to me that the sensors are sending readings to the computer to determine if the truck is running rich or lean and telling the computer to adjust the mixture.

1st Question: Is this condition (high voltage on the after Cat sensor)telling the computer that it's running too rich or too lean?

2nd Question: Do I really have to have them? Currently, I'm running with the after cat. sensor reading high voltage. The before cat sensor is currently unpluggedand gives no error code. I unhooked it because I thought that was the sensor that was bad since the other had been replaced less than 40K miles ago. Apparently, I screwed up the pins when I tried to re-connect it - so, I'll have to cut off the plug and hardwire it - just haven't had time. Took it back by Auto Zone to check to see if there was an error code for the other sensor (Bank 1 Sensor 1) and there was not. Truck doesn't run any different without it and I've seen no significant drop in Gas Mileage (average 13 MPG City - 15 to 16 MPG Highway at 75 MPH.) So, other than getting rid of the CEL, is there a reason that I should spend the $75 for the sensor? Again, it runs no differenty - I read the posts regarding rough idle, etc.

Would a performance chip get rid of the CEL with no sensors or is there a way to get rid of the CEL and have no sensors?

Advice?

 

this might help a little. http://www.gnttype.org/techarea/ecms...O2sensors.html
#1 i understand the article to say this. see quote below... high voltage within the normal range indicates rich, not all fuel burned, and no oxygen present. lower voltage indicates lean, all fuel burned up, and plenty of additional oxygen present.

#2
i'm not quite understanding your setup. i understand you have true duals, but where are your o2 sensors ? both on one side, or one on each side ? its my understanding that the pre-cat sensor is the most important, as it controls whether the engine can go into closed loop mode for best trim, and best mpg. otherwise it stays in slightly more rich open loop mode. the only purpose of the post cat is is to provide feedback for the pcm, so that it can compare the pre-cat reading to the post-cat reading, to verify the cat is doing its job. i know there are o2 simulators for the post-cat, but i'm not sure about a pre-cat. (i'm assuming your truck's model year only had 2 o2's). i would just guess that it would be practical to place the one pre-cat o2 in one side, and then use a sim for the post cat o2. one source for sim's is dan the fastmann - you might want to call and talk to him for an expert opinion.

quote from ...
An Oxygen sensor is a chemical generator. It is constantly making a comparison between the Oxygen inside the exhaust manifold and air outside the engine. If this comparison shows little or no Oxygen in the exhaust manifold, a voltage is generated. The output of the sensor is usually between 0 and 1.1 volts. All spark combustion engines need the proper air fuel ratio to operate correctly. For gasoline this is 14.7 parts of air to one part of fuel.

When the engine has more fuel than needed, all available Oxygen is consumed in the cylinder and gasses leaving through the exhaust contain almost no Oxygen. This sends out a voltage greater than 0.45 volts.

If the engine is running lean, all fuel is burned, and the extra Oxygen leaves the cylinder and flows into the exhaust. In this case, the sensor voltage goes lower than 0.45 volts. Usually the output range seen seen is 0.2 to 0.7 volts.
The sensor does not begin to generate it's full output until it reaches about 600 degrees F. Prior to this time the sensor is not conductive. It is as if the circuit between the sensor and computer is not complete. The mid point is about 0.45 volts. This is neither rich nor lean. A fully warm O2 sensor *will not spend any time at 0.45 volts*. In many cars, the computer sends out a bias voltage of 0.45 through the O2 sensor wire. If the sensor is not warm, or if the circuit is not complete, the computer picks up a steady 0.45 volts. Since the computer knows this is an "illegal" value, it judges the sensor to not be ready. It remains in open loop operation, and uses all sensors except the O2 to determine fuel delivery. Any time an engine is operated in open loop, it runs somewhat rich and makes more exhaust emissions. This translates into lost power, poor fuel economy and air pollution.

 

O2 Sensors are one in each pipe.

Can you give me some contact info for dan the fastmann?

 

here is Dan's contact info:

http://www.thefastman.com/contact.asp

 

Only the pre-cat sensor indicates rich/lean condition. The post-cat sensor indicates proper cat operation. The pre-cat should show a sine wave output (as the PCM purposefully aims high and low on fuel/air ratio). The post-cat sensor should show a steady high voltage (low O2 presence) indicating the cat is oxidizing any unburned fuel. If the cat is bad ... the post-cat sensor's output will mirror that of the pre-cat sensor. You need to hook up the pre-cat and get a sim for the post-cat.

 

Hey Sir,
Does dodge oxygen sensor detect lack of oxygen underneath the carriage of a vehicle? Is it possible that an oxygen sensor will cause the engine light to turn on because it is working due to the manifold exhaust being cracked?

---newbie.

 

If I have my cat holed, the O2 sensor will read good values???

 

Buy 'em here when you need em. Been using them for years.
http://www.oxygensensors.com

 

what if (as in my case)your muffler is hanging down and all ripped to hell and air from outside is being forced back to the post sensor.Would it tell the pcm that my engine is running lean?Or to get a little more power you could in theory put a resisitor inline to the post cat and tweak your air fuel mixture?Or maybe drrrrrrr now i'm confused!!! LOL