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 ...
JPhi1618's user avatar
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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
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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
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
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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

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.
Ben's user avatar
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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 ...
Ben's user avatar
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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 ...
Zaid's user avatar
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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 ...
Zaid'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

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

P1135 code on 2003 Toyota RAV4

TLDR: The sensor is difficult to check because the current change it produces is too small for most clamp meters, so you would have to cut the harness to test it. Not recommended. Try checking for bad ...
cdunn's user avatar
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Oxygen sensor malfunction

Bad O2 sensors can contribute extra heat to the system, but usually they have the opposite effect. When the ECU detects that the sensors are faulty, the engine will default to open-loop mode, which ...
Bryan Davis's user avatar
4 votes

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

The Red/Yellow wire is in the harness, not on the O2 sensor. It's can only be something that effects all 4 sensors. The ground is provided individually for each sensor by the PCM so it can't be on ...
Move More Comments Link To Top'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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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
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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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My Toyota fails under full throttle but not when feathered

Hard to say with the information given. Sounds like retarted timing or not enough air or fuel (too rich / lean) . A repair manual will be infinitely useful in testing/troubleshooting. Things to ...
rpmerf'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
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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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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
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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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