Common OBD Two Codes
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. Read more
Car AC Diagnostics
AC Manifold Guages
It may seem crazy to talk about car AC diagnostics in the middle of a snow storm. But by the time this page gets indexed and ranked you should be ready to turn on your vehicles air conditioning for the first time after a long winter of not using it.
On a previous post about air conditioning auto repairs I discussed how to test your system using manifold gauges. We also discussed how important the total charge of the system is to air-conditioning performance.
On this page will be some tips on how to deal with pressure readings that are out of specifications. Also included will be some best practices for Car AC diagnostics as well as running system AC performance testing properly. And don’t forget to wear safety equipment because freon is dangerous.
High side pressure readings
When you’re basing your diagnostics off of system pressure it is very important to refer to the pressure charts in your online auto repair manuals. These pressure readings will vary greatly with humidity and outside temperature.
Improper diagnosis is often caused by expecting an unrealistic reading on a hot humid day. With that said if you have determined that your pressure readings are truly off here are some tips on what they could actually mean. Read more
Slipping Automatic Transmission
96 GMC K1500 4WD
A slipping automatic transmission is the first sign of serious internal troubles heading your way. More often then not this condition will lead to a complete transmission overhaul. Here is an email question about this common condition as well as a good example of the likely symptoms.
A visitor writes, Thank you for your website. You have pushed me to further educate myself about the mechanical side of cars. Here is some information about my trucks problem before I take it to a transmission shop or general car repair place.
I have a 96 GMC K1500 4WD. I am having slipping automatic transmission problems. If I drive like grandma and ease up to Highway speeds I can feel all gears engage and pull, 1, 2, 3, and 4. If I take off fast From a stop or if I’m driving 6Omph and stomp it for passing gear I can see the Rpm gauge surge to 3500-4000 and hear the engine running great but no power at The wheels.
I have to let off the gas for the transmission to begin to pull again as it falls back to the higher gear. My auto scan tool from Actron says I have no codes set in the computer. I have purchased the all data online auto repair manuals for my trucks. I have gone through the related info to become familiar as possible with this problem. After a physical inspection, my fluid level is correct and no burnt odor. I have no leaks, the wiring harnesses and connectors look fine. Read more
Automatic Transmission Fluid Service
Automatic Transmission Fluid
This post is about checking and changing automatic transmission fluid. At the bottom ( Click the read more Link ) is my personal story about the 4L60E transmission in my Chevy Blazer.
First I wanted to make it clear that I am still undecided on whether changing the fluid in your automatic transmission is the right thing to do.
I have seen studies that support both sides of the question. I work for a large fleet company that tested several hundred vehicles and monitored the performance and failures of the automatic transmissions.
The private study conducted by the fleet showed that there were just as many failures in the vehicles that had regular transmission services as the ones that received no transmission services.
With that being said I generally recommend them. For myself I follow the manufacturer’s guidelines for transmission fluid and filter changes.
Just from experience in talking with customers it would seem that most drivers put this service on the back burner. Checking the transmission fluid before service begins is always a good idea.
Checking automatic transmission fluid
Make sure your vehicle is on a level surface. Not all transmissions will have a dipstick but most still do. If your transmission does have a dipstick make sure you wipe the dirt off around the cover of the dipstick handle before you pull it out of the tube. This is to prevent dirt from falling down the tube and into the transmission oil. Read more
Engine Runs Rough
Rough Running Engine
Let us not forget that the engine runs rough condition can be caused by basic car problems. Many times professional and do it yourself auto mechanics start searching for answers in the vehicles high tech areas.
In many cases, the car problem is located in the most basic principles of engine operation.
Not all engine performance problems are directly related to on-board computers, throttle position sensors, fuel injectors or other fancy electronic systems.
This is the reason that all types of mechanics will still need to understand basic engine operation, as well as time tested engine testing procedures.
These basic tests are an important part of modern day engine troubleshooting and this will not change for some time. Well at least not until the electric vehicle is the only car on the roadways. Read more
Automotive Front-end Alignments
Wheel Alignment Rack
This page is about front-end alignments and why it is so hard to get a good one. Even though this is not a do it yourself auto repair, it’s good to know what you’re up against to actually receive a quality wheel alignment.
Many DIY car mechanics (myself included) will replace the front-end parts that are required, and then take the vehicle in for the alignment.
This is a good plan, but you want to make sure the auto repair shop follows through by setting all adjustable angles.
On my short list of things to ask for when you pay for a wheel alignment is to get before and after printouts. All modern day alignment racks have vehicle specifications and printers built into the equipment.
The print out will have the specifications or the factory wheel alignment settings that the vehicle should have. Also on the print out will be the before readings for Castor, camber, and toe in settings. And last but not least, the final readings after all the adjustments are done and locked.
Even if you do not have experience with alignment settings, you should still ask for these before and after prints. When you begin to study the final settings you can compare them to the factory specifications to be assured they are within tolerances.
More often than not, when this request is made, you will find that the technician will go the extra mile to make sure his educated customer is satisfied with the alignment.
Read more
Replacing Spark Plugs
Denso Spark Plugs
Replacing spark plugs has always been a favorite task of do-it-yourself auto mechanics. The interesting thing about this maintenance operation is that on some vehicles it is fun and easy.
On other automobiles the task is extremely difficult and sometimes the path of success is plagued with extreme problems that could lead to pulling the cylinder head.
Sometimes when spark plugs are removed from a cylinder head the threads will have traces of metal on them.
Each spark plug removed should be numbered with the cylinder it was removed from and inspected thoroughly for this type of thread damage. This type of car problem happens more often on engines that use aluminum cylinder heads.
If you run into this problem when performing your own sparkplug maintenance it is highly recommended to correct the condition before reinstalling the plugs. Patience and care at this point can save you from major auto repairs down the road. Read more
Manual Transmission Diagnosis
Transmission Repair Manual
Last week’s post was about manual transmission diagnosis and repair. This week I will dive a little deeper into actually diagnosing problems.
Surprisingly, information about manual transmissions is not that easy to find on the Internet. That is why I decided to post a few more times about this subject.
But keep in mind the most accurate information is available in your vehicle specific auto repair manual. This should list the most common problems associated with, your transmission and/or trans-axle if you have a front wheel drive car.
Here is also a Amazon link for the how to rebuild manual transmissions
Many problems that seem transmission related may actually be caused by defects in the clutch assembly differential or drive shaft areas. Check these areas along with your standard diagnosis, particularly if you are considering removing the transmission for further inspection or repair.
Visually inspect your manual transmission
RWD Manual Transmissions
Before you start grabbing wrenches and removing bolts it is always recommended to perform a really good visual inspection. Here are five of the things that you should check for.
1) Check for looseness of the transmission by pushing up and down on the unit from the tail shaft (a pry bar in the right place makes this easier). Take a look at the transmission mounts to see if the rubber separates from the metal plate. If the case moves up but not down. The mounts may require replacement.
2) Check for lubrication leaks at all of the gasket and sealing areas. On manual transmissions the output shaft seals or rear trans seal where the front drive shaft yoke slides in is prone to leakage. So don’t miss taking a look at this tail shaft seal.
3) Check the case body for signs of porosity that show up as a leak or seepage of lubricant. Aluminum housings can have small imperfections that allow transmission fluid to leak out of areas that are not sealed by gaskets. Read more
Manual Transmission Facts
Manual transmission repair diagrams
A manual transmission can be quite sturdy if operated and maintained properly. This is one component that should last the life of the vehicle without any major breakdowns.
Although modern units with cases made from aluminum are not as strong as the “Rock Crushers” that Chevy put out in the late 60’s they are less then half the weight.
This of course increases fuel economy by reducing weight. But also can reduce the tolerance of being run low on fluid. Case damage on a newer trans will usually call for replacement.
These modern day manual units are designed so the internal working parts will operate in a bath of oil circulated by the motion of the gears and the shafts inside.
Some of these units will use oil slinging technology to through oil were it is needed most. This is similar to splash lubrication used in modern automotive engines.
Some manufacturers use a pump and tubes to circulate oil to critical areas that require more lubrication than the natural circulation would offer.
Manual transmission fluids
Providing good internal lubrication is the key to the longevity of the transmissions life. If the amount of lubrication falls below the minimum levels or if the trans fluid becomes too dirty major problems can result.
Note that most car makers do not offer fluid filtering on a manual trans. But instead may have magnets inside to pull metal shavings out of the fluid. These magnets can aid in trouble diagnosis as they will hold the worn material for inspection. I have more information about the insides and how to learn manual transmissions.
Transaxle Manual Shift
Different car manufacturers will often use different transmission fluids in their units. The internal assembly procedure and tolerances are specifically designed to operate with this specific fluid installed from the factory.
Installing the wrong kind of manual transmission lubricant can affect the overall protection of the internal moving parts.
An example would be if the transaxle were designed to use automatic transmission fluid. If 75W90 gear oil is installed in replacement of the transmission fluid, inadequate lubrication is most often the result. Read more
