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8 votes
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Can a car operate without a catalytic converter?

Most vehicles which are OBD-II compliant (newer vehicles are a little different) use just the O2 sensors located before the cat to adjust the air/fuel ratios. The in-cat or after-cat O2 sensors are ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
7 votes
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Locating the O2 sensors and the cat along the exhaust

Picture 1 is the downstream 02 sensor. Upstream is located on the exhaust manifold. Picture 1 contains both convertors. Picture 2 is the exhaust resonator.
Ben's user avatar
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7 votes
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Are widebands known to go lazy over time?

We found at least two issues The air filter housing wasn't forming a proper seal with the MAF sensor This engine boasts a quirky design where the MAF sensor sits at the back of the engine. The air ...
Zaid's user avatar
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7 votes
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Do oxygen sensors degrade over time or just break?

O2 sensors become lazy over time. They do not respond as quickly as they do when they are new. If you have a graph plot of them when new, you'd most likely be able to tell the difference, however, ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
6 votes
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Removing stubborn o2 sensor - danger of stripping thread?

If they told you the truth and unsuccessfully tried an acetylene burner: Well, yes: What does not get loose with such measures will (most likely) damage the thread (if that not already happened) if ...
Martin's user avatar
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6 votes
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O2 Sensor Problems

This is a bad idea. There's a very good reason why ECU's default to running on the rich side when they are unable to get a valid reading from the O2 sensor and that is because running an engine too ...
motosubatsu's user avatar
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5 votes

Shouldn't my post-cat O2 sensors (lambda probes) be reporting varying numbers?

Here's how to decipher INPA lambdaintegrator Short-term fuel trim. Both banks have a short-term correction of 28%. This should settle down to 0% fairly quickly, so the fact that it stays red ...
Zaid's user avatar
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5 votes

1998 Honda Civic - O2 sensor or catalyst failure?

Excellent graphs. The after catalyst sensor shows normal mixture readings. The PCM can and will operate the system lean or rich depending on operating conditions. The voltage will rarely be held at ...
Fred Wilson's user avatar
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5 votes
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Why does an engine revving at 3000 rpm produce O2 variations of 1-2 Hz?

Upstream Variation (Hz) is also called O2 crosscounts, this normal fuel mixture control, the fuel computer changes mixture ever so slightly so it crosses the stoichiometric boundary (.45v), back and ...
Moab's user avatar
  • 7,990
5 votes

Driving without oxygen sensor

Which sensor was removed? Pre- or post-cat? If pre-cat, it could be causing the engine to run differently. If post-cat, it's just noise and your engine shouldn't be running any differently ... it just ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
4 votes

My lambda sensor has a collar around it, I can not see how to unscrew it. (2009 Ford Fusion)

It should look something like the following picture. The flats for the wrench are at the bottom so you may not be able to see them depending on the location. They also might be covered by a heat ...
Move More Comments Link To Top's user avatar
4 votes

EFI engine car failed Emission test?

Before suspecting a bad O2 sensor... You need to be sure that the replacement MAF is suitable for your car. You mention the replacement MAF is a 5-pin and not a 4-pin like the one originally on the ...
Zaid's user avatar
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4 votes
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Is the after catalyst oxygen sensor used for engine mixture control?

The rear fuel control controversy has been the subject of some interest on professional automotive repair forums in years past, principally i-ATN. Rear fuel control strategies are used extensively; ...
Fred Wilson's user avatar
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4 votes
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Identifying faulty O2 sensor with scan tool

These sensors look normal. Bank 1 sensor 1 should cycle about twice per second, this is a bit slow but fast enough to maintain normal fuel control. It is common for Toyota to cycle the system a bit ...
Fred Wilson's user avatar
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4 votes
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Fixing an exhaust leak at the O2 threads

A copper washer could be a better bet - your anti-seize is designed to stop threads seizing so as it is not primarily designed to seal them it may not, however you could be lucky and it will.
Solar Mike's user avatar
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4 votes
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Should I replace oxygen sensor? Which one?

You don't absolutely need to install a new O2 sensor, however there are some huge drawbacks to doing so. As the mechanic stated, it doesn't affect how the engine runs. The downstream O2 sensor (in ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
4 votes
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Oxygen sensor "clean air source"?

According to Auto Service World, oxygen sensors requiring reference air can get it in several ways: Some O2 sensors were designed with laser welded “waterproof” housings and thereby seal the ...
David Bailey's user avatar
3 votes
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Interpreting O2 sensor readings

While you have a general grasp of what is happening, the information is rather incomplete. First, a catalytic converter does absolutely nothing with carbon dioxide (CO2). The CO2 just passes through....
vini_i's user avatar
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3 votes
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What options do I have for installing an O2 sensor in a cast iron exhaust manifold?

You can drill and tap a cast iron, yes, only difference - it is more fragile than steel, but it should not slow you down. Other option is to weld it in lower part, where the steel pipe starts. It ...
Arturs Bolsunovskis's user avatar
3 votes

Shouldn't my post-cat O2 sensors (lambda probes) be reporting varying numbers?

It may depend on how you are gathering that data. Perhaps a "Live Data" OBD Parameter ID or "PID"? You may need a more specific scan tool or smarter software. Some (especially higher end) vehicles ...
SteveRacer's user avatar
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3 votes
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EFI engine car failed Emission test?

It sounds a lot to me like it could be your car's O2 (lambda) sensor in the exhaust. From wikipedia Oxygen sensor Function of a lambda probe Lambda probes are used to reduce vehicle emissions by ...
Steve Oakes's user avatar
  • 1,096
3 votes
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Do engines absolutely need an O2 sensor to function properly?

Before fuel injection and catalytic converters, carburetor engines ran without many (or in some cases, any) electronic sensors. They'd use mechanical springs, grub screw adjustments and vacuum pipes ...
Steve Matthews's user avatar
3 votes
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What would cause those two codes?

Your DTC descriptors are a bit off. P0144 is, Third HO2S (Sensor 3) Circuit High Voltage. P1130 is, Secondary HO2S (Sensor 2) and Third HO2S (Sensor 3) Replacement Required. Check your voltages at ...
Ben's user avatar
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3 votes
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Can the same O2 sensor provide narrowband and wideband output simultaneously?

Maybe not the sensor itself, but there are controllers that can perform the conversion. They are capable of simulating the narrowband signal using the wideband O2 reading and send it to the ECU, ...
Zaid's user avatar
  • 39.2k
3 votes

Trouble rewiring O2 sensor harness after dogs ate it

Here's what I found: (Zaid has a good answer, but sometimes on a four wire sensor the ground is floating inside the ECU [as with your Yukon] - which makes his "Step 2" not always reliable. Still, in ...
SteveRacer's user avatar
  • 12.4k
3 votes

Do oxygen sensors degrade over time or just break?

It may be anecdotal or marketing hype. I did see a demonstration where they compared sensors with 80,000 miles on them with their Brand X new units. While the final results were the same the new units ...
mikes's user avatar
  • 19.9k
2 votes

P2238 Positive Current Circuit Low on Toyota Camry 2004

A 2004 Camry SE uses three sensors: an Upstream Oxygen Sensor, an Upstream Air Fuel Ratio Sensor and a Downstream Oxygen Sensor. Your "Bank 1 Sensor 1" error indicates a problem with Air ...
Raul Tennis's user avatar
2 votes

How to Unscrew/loosen stuck O2 sensor

First, try a combo of 50/50 ATF and acetone with a O2 sensor socket wrench, extension bar if needed, and a breaker bar. If that doesn't work, you can try some breaking blows with a hammer and try ...
Sarah's user avatar
  • 21
2 votes

Check engine lights came up after Air filter change?

Milan, I recommend that you purchase a paper Chilton's or Haynes repair manual for your car. They cost around $30 at your local autoparts store. Many manufacturers have provided a 'secret' code that ...
zipzit's user avatar
  • 6,559
2 votes
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Must the voltage of the post-cat O2 sensor cross 0.5V?

Your graphs look very normal. No, the post cat sensor will remain a nearly flat line when the engine is a steady speed, if the catalyst is good. It can and likely will lean or rich as the PCM chooses ...
Fred Wilson's user avatar
  • 11.6k

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