Tag Archives: check engine light

Using Snapshot Mode on Automotive Scanners

automotive scanner snapshot mode

Actron 9580 snapshot scan tool

I get a few questions about using snapshot mode on automotive scanners. It is one of the features I use often when the diagnosis is getting complicated. It’s one of my favorite features of the tool because it can also be useful in pinpointing intermittent car problems that can be difficult to find using other reliable methods.

Let’s say you have an intermittent problem that is caused by a loose or corroded electrical connection to an automotive sensor. The problem turns on the check engine light or causes an issue when the vehicle hits a bump or slams a pothole in the road. The automotive scanner with a snapshot mode can provide data for diagnosis.

Information from the data stream can be reviewed right before and after the vehicle hits the bump or pothole. I have written some reviews of automotive scanners in several price ranges and a few of them are capable of taking these diagnostic snapshots of the data stream. When it comes to Diy auto mechanics it seems that this feature is underutilized.

The Automotive Computer is Your Friend Continue reading

Before You Replace the Oxygen Sensor

image of common oxygen sensor

common 4 wire oxygen sensor

Before you replace the oxygen sensor on your vehicle let me make an opening statement. In my own personal opinion this is one of the most often replaced sensors. To make matters worse way too often it doesn’t fix the problem with the car or truck.

In most cases this sensor is not a returnable item at your local parts store, because it is considered an electronic component. This is to avoid the try it out before you buy it out driveway warrior. Another problem with replacing the oxygen sensor is deciding which one to replace.

Most vehicles have at least 2 of them installed and four sensor systems are even more common. They’re installed in the exhaust stream to sample the exhaust gas.

A check engine light diagnostic trouble code can be set if the part is bad or if the exhaust gas itself is out of balance from a fuel system problem. So how do you determine which oxygen sensor is bad if any. First let’s learn about what an oxygen sensor does and why.

What does an O2 Sensor do

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Testing Oxygen Sensors

Testing O2 Sensors

oxygen sensor

Heated oxygen sensor

Testing oxygen sensors before replacing them is a good idea. This might not be the most common check engine light code but it is very high on the list of would be codes set in the computer’s memory. There are also many different types of oxygen sensor problems.

Often when a mechanic pulls one of these codes his first reaction may be to just go ahead and replace the sensor. There are more than 30 different codes that relate to the oxygen sensor circuit.

Some of these codes are dedicated to the heating circuit and some are dedicated to the power supply. But I believe by far the most common codes relate to the activity and efficiency of the sensor itself.

Not only can there be a wide variety of problems with the circuit that will throw a code for this exhaust stream sensor but vehicle problems can cause the code to set as well. One of the most common problems would be a vacuum leak that throws off the air fuel mixture providing a lean condition that can eventually set a code for lean exhaust.

Diagnosing Oxygen Sensor Parts Continue reading

Common OBD Two Codes

fuel tank caps

Locking gas cap

One of the most common OBD two codes would be for the evaporative emissions system. These codes were designed by the manufacturer and mandated by clean air laws.

Basically this is that the fuel system on every automobile must be completely sealed. No longer are you allowed to vent fuel vapor into the atmosphere.

This means that a storage and burning system is necessary to properly handle the naturally occurring fuel vaporization process.

Depending on the year make and model of the vehicle the codes set will usually be in the P0400 range. These codes when set will help you determine what the problem with the system may be.

When the fuel vapor system is determined to be leaking the severity of the leak is measured. Individual codes may set for a small leak, a medium-sized leak, or even a large fuel vapor leak.

Also in the P0400 range of codes will be specific codes for the canister and purge valve functions of the evaporation emissions system. All of the failures in the P0400 range could be considered common OBD codes. Again depending on the year make and model of the vehicle. But I have seen failures in all parts of the evap at one time or another.

OBD two evap systems leaks

OBD two monitors the evaporative system by testing the ability of the fuel tank to hold pressure as well as purging the system to vent petroleum fumes from the charcoal canister storage device. The most common way that this pressure test is deployed is with a small pump. Continue reading