17 votes
Accepted

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
Accepted

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 ...
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
Accepted

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 ...
7 votes
Accepted

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
Accepted

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
Accepted

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, ...
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 ...
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
Accepted

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 ...
  • 7,988
6 votes
Accepted

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 ...
  • 9,856
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

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 ...
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 ...
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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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
Accepted

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 ...
4 votes

Why would a lambda sensor fail?

Lambda sensors have several different failure modes. Heater element. The heater element is a resistive material that resists electron flow thus producing heat. This is the most common cause of early ...
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4 votes

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

I haven't been able to find any solid conclusions on the VW forums regarding the root cause for this behavior, but there are some clues as to what could be causing this from the diagnostic code. Fred ...
  • 39k
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 ...
4 votes
Accepted

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 ...
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 ...
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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 ...
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 ...
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