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

Car Computer

When you get right down to it the primary purpose of OBD II is to make the diagnosis of many automotive problems less complicated. Note that OBD II was deployed on vehicles beginning with the model year 1996 and is still used on present day automobiles. This latest generation of on-board computers also brings a uniform diagnostic platform across all vehicles whether they are foreign or domestic.

One of the things that’s included in this standardized diagnostic protocol is the snapshot feature. Some mechanics call this feature freeze frame mode instead of snapshot but it is basically the same thing. My definition of it is the computer’s ability to record data from all of the sensors and actuators at a time when the system turns on the check engine light or sets a pending fault.

General Motors has taken this one step further and expanded the capability to include failure reports which does the same thing as the snapshot or freeze-frame but also includes any faults stored in the memory. Not just those related to the emission control system. This is helpful because a failure report can include information from the transmission control module responsible for transmission shifting and operation as well as the body computer that is responsible for ABS braking systems, traction control and airbag information on many vehicles.

The basic advantage of using snapshot mode on automotive scanners is the ability to look at the existing conditions when the code was set. This is especially valuable for diagnosing intermittent problems as I mentioned above. Whenever codes are set a record of all related activities is stored in the main computer’s memory. This record allows the mechanic to look at the action of the sensors and the actuators at the time the code was triggered. This can often help identify or pinpoint the cars problem.

I love automotive scanners

Auto Scanner Kit

When I started this article about using snapshot mode on automotive scanners I realized that it sounds more complicated than it actually is. The automobile scanners that are available today provide excellent documentation usually in the form of a CD that ships with the tool. It does a good job of walking you through the different features that the tool is capable of including the freeze-frame or snapshot mode.

A wide variety of car Scan tools are available today. The strength of the included documentation will vary depending on the make and model. I have seen people complain about the directions included with some off brands. When you boil it down the scan tool is a microprocessor designed to communicate with the vehicle’s computer. It is connected to the OBD II diagnostic connector that is usually located just left of the steering column.

The scan tool can access trouble codes, run tests and if it is capable of reading the data stream it can show you the activity of the different sensors in the system. Most people buy these scan tools and just use them for pulling trouble codes and maybe resetting the check engine light. If you spend the money on one these scan tools why not take the time and learn how to get the most out of it! For more recent articles this next link will take you back to the auto repair information blog homepage.

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 are 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?

Universal catalytic converter

The signals from the upstream (before the catalytic converter) and the downstream (after the converter) exhaust gas oxygen sensors are used by the electronic control module or the main computer in the vehicle to monitor the current air fuel mixture.

This sensor is a key input signal that will help the vehicle meet or exceed the emissions requirements in the State that it operates in. It will also affect the overall fuel economy of the automobile. This is important to the manufacturers because they are required to meet minimum standards for fuel economy. This is known as c.a.f.e. or corporate average fuel economy. If the car falls below the Government standards it is subject to a gas guzzler tax when purchased new.

The oxygen sensors are threaded into the exhaust pipe near the engine and on some models are threaded into the exhaust manifold. The signal from an oxygen sensor is based on the amount of oxygen contained in the exhaust gases being expelled from the cylinders.

When the sensor signals indicate that this mixture is lean the computer increases the fuel mixture to the engine by increasing the injector on time. When the sensor is reading a rich exhaust mixture the computer would lean the air fuel mixture by reducing the fuel injector on time.

As a rule of thumb if the oxygen level is higher the voltage signal from the oxygen sensor will be low (below 500mv). Likewise if the oxygen level is low the sensors output will be high (above 500mv). This can be important when diagnosing oxygen sensor problems.

Heated o2 sensor

Because the oxygen sensor must operate properly quickly from a cold start most late model engines use a heated oxygen sensor. These sensors have an internal heating element that allows the sensor to reach its optimal operating temperature more quickly and maintain its temperature during periods of engine idling.

Now that the oxygen sensor has become so complicated they are capable of setting many different kinds of trouble codes. There are separate codes for heating system malfunctions as well as the response time of the oxygen sensor, overly lean or rich conditions detected, as well as onboard sensor diagnostics such as resistance determined by a reference signal.

With all the possibilities of things that can go wrong with the oxygen sensor it’s self, there are even more possibilities in the surrounding systems that can set trouble codes. This can make the oxygen sensor appear to be the problem. You can save yourself some time and money by following the individual diagnostic chart for the trouble code that is set in the vehicle’s memory.

These diagnostic tree charts take into account that the oxygen sensor may be indicating a symptom and not actually be the problem with the vehicle. You can visit my other site to learn more about web based versions of the car repair manual. For more articles on this website you can visit the homepage for more auto repair information.

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.

Test the oxygen sensor

If you set a check engine light for an O2 sensor heater circuit problem it would be wise to make a few checks before you replace the part. If the O2 sensor heater is not working the sensor warm-up time is extended and the computer will stay in open loop longer. This can cause high engine emissions and poor fuel economy due to a rich mixture.

Testing oxygen sensors heater circuit can be performed by disconnecting the sensor connector and connect a voltmeter between the heater voltage supply wire (harness side) and ground. With the ignition switch on 12 V should be seen on your meter. If you have the proper voltage then you know the heater circuit is operating properly all the way down to the sensor.

You can then take your automotive meter and go from the heater terminals on the sensor side of the connector and take a resistance value. If your meter shows open (OL) and no resistance is present then this would be a strong indication that the heater has failed in the oxygen sensor itself.

Using a scanner to test oxygen sensors

Good auto scanner

I know not everyone has an auto scanner. But this is one of the best ways to test oxygen sensors. The automotive scan tool has come down in price over the years and one that is capable of testing oxygen sensors can be had for under $200.

When you pull the oxygen sensor data stream up on your auto scanner the output voltage from the sensors should constantly cycle between high and low voltages as the engine is running in closed loop. This cycling of the voltage is actually the result of the computer constantly correcting the air fuel mixture in response to the feedback from the exhaust stream sensors.

When you are watching the output voltage it should move quickly between high and low voltages in mili volts. If the response is slow the sensor could be considered lazy and might need to be replaced. As a rule of thumb, with the engine RPMs at about 2000 the sensor should cycle from high to low between 20 and 40 times in a 20 second period. If the voltage is fixed and does not move or moves very sluggishly this could be a sign of a bad sensor.

Buying an auto scanner and testing oxygen sensors before replacement can save you money in the long run. On modern vehicles there are usually at least four sensors (2 upstream and 2 down stream). The average cost of this part being around $100 and in most cases the part is not returnable. Too often I see money wasted on replacing good sensors.

In closing I would like to mention that when I run across a vehicle that has set a check engine light code of any kind I prefer to follow a diagnostic chart in the car repair manual for that specific problem. For more of the latest posts visit the auto repair information blog home page.

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.

In this type of system the powertrain control module tests the evaporative emissions system by energizing the pump. As pressure builds the cycling rate of the pump decreases. If there is no leakage in the system the pressure builds until the pump shuts off.

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If there is a leak pressure does not build up and the pump continues to run until the test cycle is completed. If no leaks are detected by this test cycle the powertrain control module will move on and test the purge cycle.

Some systems have purge flow sensors between the solenoid and the intake manifold. In this case the PCM monitors the signal from the sensor once per drive cycle to determine if there is vapor flow at the proper levels into the intake manifold.

Note that on some GM vehicles enhanced monitors can detect leaks and restrictions in the system as well.

In these types of enhanced systems a poor sealing fuel cap or one that is missing is capable of turning on the check engine light.

The common gas cap obd two code

I’ve put together a video that discusses these common OBD two codes. Since the fuel cap is often removed for re-fueling this has become known as the weakest link in the system. Even if the gas cap is properly reinstalled the sealing ring between the cap And the filler neck can become nicked or worn over time. This often shows up as an Evap system code for a small fuel vapor leak.

Gas Cap Code Video

Also keep in mind when you’re vehicle sets the gas cap Code the check engine light will remain on even if the problem is intermittent. It is necessary after the repair is completed to clear the codes and retest the system.

For the latest posts and auto repair information this next link takes back to the home page from Common OBD two codes.

Solutions for check engine lights

Auto Mechanic

This was an auto repair information blog when I started it two years ago. Things stayed on topic, but changed a little when gas prices started to climb in early 2008. This is also when I purchased the water 4 gas systems and decided to share the details of my project with visitors. In today’s post I wanted to return to the original reason I started this blog. And that was to supply auto repair information for people that like to fix their own cars.

After fielding many questions over the last couple years on my car repair help page I have noticed one very common piece of advice that I continue to dispense. It also happens to be the first step in almost all of my automotive diagnosis procedures that I personally use. And this is the visual inspection. It is very common that I will uncover the cause of the car problem by simply performing a thorough visual inspection.

Auto repair visual inspections

I’m going to provide some examples of what to look for, and some of the most common things that I have found. It would seem that a visual inspection during these winter months are more important then in the summer. But regardless, I perform this procedure as a quick first step in automotive diagnosis no matter what the weather is like.

My first example actually happened yesterday and got me thinking about how I should share this with website visitors. I was working on a 2006 Chevrolet 3500 series van. The driver’s complaint was the check engine light was on.

I scanned the vehicle and found a map sensor code. The first thing I did was perform a visual inspection of the map sensor, the connector and its wiring harness. The first thing I noticed was little black chips of plastic that were laying on the intake manifold. These were obviously pieces from the conduit that protects the map sensor wiring harness.

I followed the harness back and found a spot where a rodent had chewed through not only the protective conduit, but also completely through the ground wire for the map sensor. There was no need for any scientific check engine light diagnosis because it turned out just to be a quick repair of a single wire.

Auto repair diagnosis

Another example of diy car repair diagnosis. My nephew called me from up north and said that he had an ABS light on. I live in Florida now, so I was not able to work on his vehicle. But I did notice in the news that they had recently gone through an ice and snowstorm. So I walked him through some simple steps to do a visual inspection on his own car.

I explained to him where the wheel speed sensors and wiring harnesses were located. When he poked his head around the wheel, he noticed a 15-pound ice burg was stuck and pulling on the wiring harness to his left front wheel speed sensor. Since my nephew is not very mechanically inclined, he was forced to take it in for repair.

But he was armed with the information to provide the service center that saved him Diagnostic time, and also the down time of his vehicle. The weight from the ice and snow that collected on the wiring harness broke the wires where they attach to the sensor head.

Auto repair safety

My nephew would have liked to continue to drive around with the ABS light on as opposed to spending the money on car repairs. In fact, I had to talk to his mother to force the repair to be completed. Antilock brake systems are a fantastic safety feature. During winter weather with ice and snow a properly operating ABS system may save your life or at least prevent damage to your vehicle or other drivers.

In closing I would recommend that when ever you have a warning light on your dash fix it. Either using do it yourself auto repair techniques or a car repair shop. And take a few minutes to perform a thorough visual inspection that is related to your problem. External damage by rodents and road debris can be highly visible and solve your car problems.

Ford’s top-selling F 150 will also have this new system, which was unveiled at the North American international auto show. It will be in your local showrooms and ford dealerships this fall. This new feature is also coming to the 2009 crossover vehicle the Lincoln MKS luxury sedan.

This new feature may not cause people to buy the trucks, but it is something that they will appreciate every time you fill up. The quick fueling system that was inspired by Ford’s NASCAR racing experience first appeared on the 2003 Ford GT sports car with rave reviews. Now every body can feel like the refueling chief on a race car pit crew.

How do you fill a fuel tank without a gas cap?

The race car inspired system has two small spring-loaded tabs that pull back a flap inside the fuel filler neck as the fuel-pumping nozzle hits them. When the nozzle is pulled out a flap closes and seals the fuel filler neck automatically. Besides the convenience factor of the cap less system, there are some environmental benefits as well. The quick opening and then re-closing of the fuel filler neck allows a reduction in the escape of gasoline vapors, which is bad for the ozone and the environment.

This gas cap less fuel filling system ends another common problem that occurs when a gas cap is not screwed on tightly enough. The dreaded check engine light that appears on the dashboard because of a fuel vapor leak will be a thing of the past. The integrity or the ability of the fuel system to hold pressure is tested by the vehicles PCM on every startup in case you where wondering.

If the you are further curious about things that turn on the service engine light you can visit my updated page about common causes of the check engine light. Also note that these are things you can fix yourself.

She was driving and her check engine light came on. She called me in a panic. I told her to take it to a chain store and hope for the best but to ask for the old parts back.

The shop said the vehicle needed an o2 sensor and my sister confirmed the light was out and received the old part.

When she got back in town I asked to see her old part, it was not an o2 sensor but an egr valve off of a large diesel engine. Definitely not from her little economy car gas engine.

When I looked under her car the old original o2 sensor was still in the exhaust stream.

To make a long story short the shop just cleared the check engine light and let her go after confirming with her she was heading back to her home state.
Two things to learn from this. One if you have out of state tags tell the shop you just moved to the state your in and have not changed your tags yet.

The shop knows that if you are a transient customer that they will never see you again and can give you the royal screw over with no problems.

The second lesson is if you ask for the old parts back know what the part looks like.

Have the shop show you the old part on the car before they remove it so you can confirm it is the part quoted in the repair estimate.

Learning some basic automotive skills will make you feel more confident about going in for auto service. The service writer or service manager will instantly recognize this confidence.

A consumer that understands the vehicle and how the auto service business works is usually passed over when it comes time to apply the rip offs and scams.

For more information on check engine light diy diagnosis. For more info on protecting yourself from auto repair rip-offs.

check engine light auto repair car repair auto scan tool