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 mechanical LSD mechanism is advantageous in that it has good response of the LSD differential limiting force to the engine driving force and has direct vehicle operational stability allowing the driver to easily grasp changes in the vehicle behavior. This post discusses these advantages in comparison with conventional DCCD system.
The Driver’s Control Center Differential system is system that appropriately controls the differential limiting force of center differential LSD depending on running conditions of a vehicle. The DCCD system evolved provides controls that follow operations of the driver, while conventional DCCD system provides those based on conditions of the vehicle.
The system consists of a center differential of planetary gear type provided with LSD function, a steering angle sensor, a yaw rate sensor, a lateral G sensor, a DCCD control module and other components.
Hybrid LSD mechanism using conventional electromagnetic clutch LSD mechanism added with torque-sensitive mechanical LSD mechanism allows approximate coincidence between the vehicle acceleration/deceleration and LSD clutch differential limiting timings, resulting in linear LSD characteristics acquired through driver’s accelerator operation. Thus, the driver can more freely control the vehicle by easily grasping behavior of the vehicle.
In addition, the steering angle sensor let the DCCD control module know the driver’s intension of turning. In combination with the yaw rate and lateral G sensors, it adjusts the electromagnetic clutch LSD differential limiting force based on the running path imaged by the driver and the actual behavior of the vehicle. Thus, cornering in better accordance with the driver’s image is enabled, preventing occurrence of understeer and oversteer.
For balancing between the vehicle turning performance and traction during turning in a high order, the center differential driving torque is set to have distribution ratio 41:59.
Manual mode switch/DCCD control dial
In manual mode, the DCCD control can be used to adjust the differential limiting force of the electromagnetic clutch LSD mechanism in the range from free to lock. Current settings of the control dial are displayed on the indicator in the meter.
The 2008 Subaru Impreza WRX STI has a heritage of power and control. Previous models have been the foundations for countless racing victories and championships. The new WRX STI promises the same with it’s 305- horsepower, turbocharged, intercooled Boxer engine and a six-speed manual transmission.
Power and control incorporate enhanced technology. As suggested by new switchgear on the dashboard and center console and my markings within the instrument cluster’s center-mounted tachometer, a driver has some things to learn before wringing out the most from the car.
Today’s electronics now allow the driver to tinker with engine response characteristics, the manner in which All-Wheel-Drive system fights for traction, and the degree to which braking and engine management help maintain vehicle stability. These capabilities are made possible by standard Vehicle Dynamics Control (VDC), Driver Controlled Center Differential (DCCD), and Subaru Intelligent Drive (SI-Drive).