Few types of diagnostic trouble codes can be more confusing than those dealing with emission problems. From the beginning of mandatory Subaru OBD2 in 1996, more codes have been added and some have changed. Here’s a look at how Subaru of America, Inc. has added and streamlined P0400-series DTCs.
Emissions-related Subaru OBD2 diagnostic trouble codes (DTCs) have evolved over the last dozen years to more precisely pinpoint the problems in automotive systems. The handful of emissions codes used for On-Board Diagnostic (OBD) systems on the late 1980s and early 1990s has grown to nearly a hundred today. Over that time, many DTCS have been modified to more accurately reflect the cause, while others have been added to the list to address issues with advancing technology.
In order to understand how these factors affect Subaru OBD2 vehicles, it’s necessary to first look at the history of emissions control, on-board diagnostics and the DTC coding system.
The amount of force exerted on wheel bearings is astounding. Each bearing is required to smoothly control the rotation of the wheel to the tune of about a thousand revolutions per mile, support the transfer of power to the wheels for rapid starts and sudden stops, and handle the powerful lateral twisting force of the tires changing direction against the pavement — all while supporting a vertical load of hundreds of pounds. And, we expect them to perform flawlessly just about forever? Not realistic.
The “Achilles Heel” of a wheel bearing is the seal. Although wheel bearings can fail due to damage, improper installation or material imperfection, the most common cause of failure is the seal losing its ability to hold the lubricating grease in and/or dirt and water out.
However, the best seal, applied to the best wheel bearing, cannot be expected to last if not correctly installed. This primer can help you properly service Subaru wheel bearings.
One of the most common concerns that any vehicle owner perceives as a problem is brake noise when stopping the vehicle. The question pops up: “What is considered to be an ‘acceptable’ level of brake noise?”
The disc brake systems used on vehicles today are designed and developed to meet many different, but very strict requirements. This must be accomplished while providing an optimum level of performance under a wide range of vehicle and environmental operating conditions.
The brake pads selected must be a balanced choice. There is a fine line between a quiet brake pad and one that will provide optimum performance under extreme braking conditions. Consequently, when a change is made in the brake pad formulation (whether it is meant to provide longer pad life, shorter stopping distances, noise reduction or a change in pedal effort), a trade-off must be made in one area or another.
An example of pad formulation change would be the industry’s switch from asbestos to semi-metallic brake linings.
The heart of any vehicle is the engine. It’s what makes it go. Anything that jeopardizes the operation of the engine can have disastrous effects and result in extensive repairs. If the engine is the heart of the vehicle, then surely the cooling system is the “circulatory system” that keeps the engine operating at optimum temperatures. If it doesn’t, bad things are going to happen.
Subaru engines are modern masterpieces of technology and precision. Manufactured of multi-alloy metals and exotic materials, these engines contain more components, weigh less, produce more power and torque and are more durable than the old iron engines of 40 years ago. However, even these high-tech engines can be damaged or destroyed by excessively high internal temperatures.
Though more energy efficient than ever before, the combustion of fuel and air in the cylinders that produces the power that propels the vehicle still creates an enormous amount of waste heat. This is carried away from the cylinders either by venting it out through the exhaust system or via the cooling system. If either of these systems fail to keep the engine at normal operating temperatures, an overheating condition occurs. Of the two, the cooling system is most vulnerable.
The cooling system can easily be contaminated or compromised by anyone putting the wrong products into the radiator or reservoir. Often, Subaru owners or service facilities that are not aware of the specific needs of the vehicle will put incorrect chemicals into the system. In fact, according to figures published by the U. S. Department of Transportation, coolant-related problems are the primary cause of mechanical breakdowns on the highway. Many of these breakdowns could have been avoided by the use of proper coolant and the right additives.
The Winter season brings cold weather to many parts of the country, and with it the traditional driveability problems.
Before you push the panic button on Subaru cold weather and driveability problems, remember:
• No vehicle runs as well when it is cold as it does when it is at normal operating temperature.
• You have been operating the vehicle in more moderate temperatures and has gotten accustomed to the way it has been running. Now it is colder and things are not working the same.
• Some areas of the country may be using gasoline blended for warmer temperatures. These fuels normally do not atomize as well in cooler temperatures.
• Oxygenated and reformulated fuels that are in use in many parts of the country are normally harder to ignite in cold cylinders.
• Many drivers get their gas at one station because it may be close to home or work. Question them about this and if this is true, suggest they try a different brand of gas. It may take a couple tanks before any improvement is noticed. Different manufacturers blend their fuels differently.
• The 4EAT has a temperature sensor in the ATF and the Transmission Control Unit (TCU) will not allow an up-shift into 4th gear until the ATF has reached a specific temperature. This 4EAT design characteristic may be interpreted as a driveability problem by a driver who is not familiar with 4EAT operation.
There are many reasons for Subaru cold weather and driveability issues during cooler weather. Spending a few minutes with your Subaru and look over the points listed above should eliminate misconceptions about the Subaru cold weather performance and driveability characteristics of Subaru vehicles.
Batteries low in voltage (below 11.6 volts) need to be specially charged. A battery at this voltage is heavily sulfated and needs either a very long, slow charge, or a very high initial charge voltage.
The battery should be left on the battery charger for at least two days. Since the acid in the battery will mostly be stratified, it needs sufficient overcharge to mix. Even after a two day charge, the battery still may only come to 60-80 percent of capacity and may need to be cycled to come to full charge. If possible, once the battery is fully charged by this method, it’s advisable to finish with a constant 1 amp for an additional 24 hours.
A battery that is below 11.6 volts can also be hydrated. This means there is lead sulfate in the separator that will form lead shorts once the battery charges. Because of these shorts, the battery may self discharge once the battery has been recharged.
Emission testing of a Full-Time 4WD or all-wheel-drive vehicle must never be performed on a single two-wheel dynamometer, nor should a state I/M program inspector or its contractors install the FWD fuse in the engine compartment. Attempting to do so will result in uncontrolled vehicle movement and may cause an accident or injuries to persons nearby.
Resultant vehicle damage due to improper testing is not covered under the SUBARU Limited Warranty and is the responsibility of the state I/M Program or its contractors or licensees.
The 1990 Clean Air Act Amendments require the Environmental Protection Agency (EPA) to implement programs to reduce air pollution from motor vehicles. Certain states are required to adopt either a “basic” or “enhanced” vehicle Inspection/Maintenance (l/M) Program, depending on the severity of their air pollution problem.
The ‘enhanced’ I/M emission testing simulates actual driving conditions on a dynamometer and permits more accurate measurement of tailpipe emissions than the ‘basic’ I/M test, which measures emissions only during engine operating conditions at idle and 2500 RPM. The ‘enhanced’ l/M test also includes a pressure check to identify evaporative emissions leaks in the fuel system.