17 votes
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Do I have to rely on wire color to correctly wire up an O2 sensor?

No, you don't have to rely on wire colors to figure out what's what. With nothing more than a decent multimeter and premix flame (blowtorch or gas stove), a two-test sequence can reveal the identity ...
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13 votes

How do lambda sensors work?

Lambda sensors, often referred to as oxygen sensors or O2 sensors, are the bedrock of any modern-day EFI system. Without them, fuel injection management is essentially flying blind and has to resort ...
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11 votes
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Is 60/40 solder fine for splicing wires that have to endure hot engine bay temps?

It should hold up. It melts at around twice the temperature where water boils, which I don't think you'll ever experience in the engine bay (unless it's touching the exhaust). But the greasiness in ...
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8 votes

How to Unscrew/loosen stuck O2 sensor

In the perfect world, you just slide a wrench on the O2 sensor and it comes out. Unfortunately since its located in a "hostile" environment (lots of heat, lots of water and potential corrosion ...
8 votes

How to Identify which O2 sensor is faulty WITHOUT readings from the car's system

This requires a bit of mechanical know-how and some time... An O2 sensor can be tested with a multimeter that measures millivolts. You'll need to securely attach one lead to the signal wire of the ...
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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 ...
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7 votes
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How to install a California oxygen sensor into a federal catalytic converter assembly?

Looking at the description of the California O2 sensor for your car, the only thing different on it (besides the internals) is the electrical plug. The wrench which you tighten it down with is 7/8", ...
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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 ...
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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.
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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, ...
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6 votes

Mass Air Flow Expected Values

Also, remember that MAF is a reading of the amount of air entering the engine. If you have a backflow issues (high backpressure) or even a timing issue where the valves are not opening and closing at ...
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6 votes
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How much improvement from replacing an O2 sensor?

I doubt you're going to be able to have someone put a number on this. I'm betting you also know that just because no error was thrown, it doesn't mean that the sensor isn't impacting performance. ...
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6 votes

How to Unscrew/loosen stuck O2 sensor

If you are going to replace the sensor and have already purchased the replacement, cut the wires off of the old sensor and put a 1/2" drive deep well socket onto it (don't use the split socket for the ...
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6 votes

2002 VW GTI 1.8T - O2 sensor fault code only when exceeding 70mph

It is most likely that this sensor has failed. The question is why does the MIL only come on above 70mph. The answer lies not in the sensor but how and when the sensor is tested by the PCM. Every ...
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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 ...
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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 ...
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5 votes

How much improvement from replacing an O2 sensor?

As @LynnCrumbling stated, this would be hard to put a number on, mainly because it depends on too many factors. This is what I can tell you. When O2 sensors get old, they don't necessarily go bad, ...
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5 votes

How to install a California oxygen sensor into a federal catalytic converter assembly?

Just to add to the other answer as I ran into this same issue, what kind of emissions do I have on my mitsubishi galant? I had this code: P0421 and I had to replace my O2 Sensor & the catalytic ...
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5 votes

A most intriguing cold-start misfire mystery

Root Cause: probably a couple of things Sadly, I feel that there isn't enough data here to uncover the smoking gun, but I have realized some things upon reflection that can indicate what is probably ...
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5 votes

2005 Crown Victoria Police Interceptor showing codes P0053, P0054, P0059 and P0060

Check fuse 21 in the under hood fuse box. If the fuse is OK at one of the o2 sensors check for power on the red/yellow wire. If you have no power at the o2 sensor I'm afraid your going to be looking ...
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5 votes

Is Torque App reliable to read O2 sensor data?

The upstream o2 on a Prius is an AFR sensor stoich reading at idle is 3.33 volts. The application isn't able to read the correct PID. So of course it would read 0v all the time.
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5 votes

How to Identify which O2 sensor is faulty WITHOUT readings from the car's system

You may want to review this answer of mine. The tests outlined there for heater resistor continuity and response to lean/rich conditions assume a fully functional sensor. If the behavior under ...
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  • 38.9k
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 ...
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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 ...
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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 ...
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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 ...
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4 votes
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How to Unscrew/loosen stuck O2 sensor

From time to time you do come across a rusted in sensor. Your vehicle being a 2001, and O2 sensors lasting some time, yours is rusted in. If sheer force does not work you may need to use an oxy-...
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4 votes
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Exhaust on a replaced motor

With the check engine light on, the car is going to be running a fixed set of parameters from the Engine Control Module. For instance Fuel Pressure will be held at max pressure and timing and spark ...
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4 votes
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Changed O2 Sensor and my mileage went down

Disconnect your battery to reset your ECU. It won't hurt, and is probably the cheapest and easiest thing you can try. 30 minutes is usually enough. There are other theories as to why your mileage ...
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4 votes

How long will my motor last having clogged catalytic converters?

If the catalytic convertor is truly plugged, you wouldn't be able to drive the vehicle, so this makes me wonder about the voracity of your statement. With a plugged cat, the back pressure created ...
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