A major component of the Subaru OBD-II system is the system’s ability to monitor the evaporative emissions system. Today’s vehicles are producing very low emissions from the tailpipe, so it has become increasingly important to monitor and contain emissions from other vehicle sources.
A potentially large source of emissions is the vehicle’s fuel system. If not properly contained, vapors escaping from the fuel tank could produce a larger quantity of harmful emissions while the vehicle was standing still than what would be emitted via the tailpipe when the engine was running and the vehicle was driving down the road.
The Subaru OBD-II system monitors the evaporative emissions system by drawing the system to a negative pressure. If the system holds vacuum, it passes the test. If the system fails to hold vacuum for the prescribed period, it fails and a diagnostic trouble code (DTC) P04440 is stored in the ECM memory. The malfunction indicator light (MIL) also comes on in the dash to alert the driver to the problem.
The charts that follow were collected through the data link connector using the New Select Monitor (NSM), during the diagnosis of a DTC P0440 on a 1997 Subaru Legacy 2.5 liter. We’ll begin with a description of system operation under normal operating conditions.
This is a simple overview on diagnosing knock sensor issues with your Subaru Impreza/Forester/Legacy/Etc.
The knock sensor is designed to sense knocking signals from each cylinder. The knock sensor is a piezo-electric type element which converts knocking vibrations into electrical signals. The electrical signal is sent to the ECM, which changes the ignition timing to reduce the engine knock or ping. For this system to work correctly, the knock sensor must first hear the engine ping. The driver of the vehicle may also hear a small engine ping. A delay of approximately 1-2 seconds is normal, depending on the fuel quality, engine load, air temp, etc. At this time, the ECM will retard the timing.
This function can be viewed on the Select Monitor RTRD mode. When the knock is eliminated, the timing is gradually advanced to the specified setting. If engine ping is heard again this process is repeated. This will continue until the knock sensor no longer hears the engine knock or ping.
Note: This is a normal operation of the knock sensor. Do not try to repair it.
The next page will discuss asking the right questions on diagnosing knock sensor failures.
This is a step by step guide on how to do a brake fluid flush on most Subaru cars. It’s often a good idea to do a brake fluid flush at least once a year to keep your Subaru’s braking system in good condition. This is even more important if you autocross or do track days with your car. Use a good performance brake fluid and not whatever is cheapest at Autozone. I have a strong preference towards ATE and Motul brake fluid. Good fluid combined with good brake pads like a Hawks or Carbotechs will give your Subaru great stopping power.
1.) Either jack-up the vehicle and place a rigid rack under it, or lift-up the vehicle.
2.) Remove all the wheels.
3.) Drain the brake fluid from master cylinder.
4.) Refill the reservoir tank with recommended brake fluid.
• Avoid mixing different brands of brake fluid to prevent degrading the quality of fluid.
• Be careful not to allow dirt or dust to get into the reservoir tank.
Air bleeding sequence (1) → (2) → (3) → (4)
5.) Install one end of a vinyl tube onto the air bleeder and insert the other end of the tube into a container to collect the brake fluid.
• Cover the bleeder with cloth, when loosening it, to prevent brake fluid from being splashed over surrounding parts.
• During the bleeding operation, keep the brake reservoir tank filled with brake fluid to eliminate entry of air.
• The brake pedal operation must be very slow.
• For convenience and safety, two people should do the work.
• The amount of brake fluid required is approx. 500
m2 (16.9 US fl oz, 17.6 Imp fl oz) for total brake
6.) Have a friend depress the brake pedal slowly two or three times and then hold it depressed.
Prior to launching the 1990 Legacy, Subaru drew attention to the car’s capabilities and durability by attempting to set world speed records with the Legacy. In an effort involving three Legacy RS Turbo Sedans, Subaru established a new 100,000 kilometer (62,137 miles) world speed record as well as 13 international records. Some of these records still stand today.
For the 1990 model year, Subaru was launching the Legacy, a front-wheel drive model with optional 4-wheel drive. It was larger than previous Subaru models and had a 2.0-liter, 16-valve, turbocharged engine. Since the car represented a new segment for Fuji Heavy Industries Ltd. (FHI), it wanted to demonstrate the vehicle’s performance, reliability, and durability. Thus began the quest for the 100,000 kilometer (62,137 miles) world record. That represents the distance typically covered during five years of hard driving.
It is not necessary to perform a cool down/idling procedure on Subaru WRX turbo models, as was recommended with past turbo models. “The current 2.0 liter turbo engine has a far greater cooling capacity and, coupled with technology advances, makes this practice no longer necessary. This explains why information about a cool down is not included in the Impreza Owner’s Manual.
The heat contained in the turbocharger begins to vaporize the coolant at the turbocharger after the engine is stopped. This hot vapor then enters the coolant reservoir tank, which is the highest point of the coolant system.
At the same time the vapor exits the turbocharger, coolant supplied from the right bank cylinder head flows into the turbo. This action reduces the turbocharger temperature. This process will continue until the vaporizing action in the turbocharger has stopped or cooled down.
Beginning with the 1997 model year, the 2.2 and 2.5 engines were made more fuel efficient, more powerful, and were given a flatter, more usable torque curve than in previous years. To achieve these objectives, it was necessary to make improvements and modifications to the Subaru engine lineup. The following are some of those improvements:
• Mechanical valve lash adjusters (reduces friction).
• Lightweight pistons (reduces inertia).
• Short skirt, Molybdenum coated pistons (reduces friction).
• Increased compression ratio (improved power output).
• Improved cylinder head design (improved cooling).
• Improved induction system (improved breathing).
As a result of these enhancements, some Subaru engines may exhibit some engine noise during the warm-up period after a cold startup. This engine noise is a consequence of the engine improvements and is not, in any way, an indication of any engine problem.
Back in 1972, Subaru introduced the Leone 4WD Station Wagon. It was the first fourwheel drive vehicle designed specifically for everyday driving, rather than for off-road or rugged use.The safety and driving performance aspects of the Leone 4WD proved popular and made the car successful. It quietly set the standard for Subaru to become the global AWD leader of today.
Subaru Symmetrical All-Wheel Drive:
Subaru calls its system of mating a horizontally opposed (boxer) engine to various types of full-time AWD “Symmetrical All-Wheel Drive.” This system is based on the balance of both the powertrain and the straight, nearly-horizontal, flow of power to the wheels.The weight of the flat boxer engine and the transfer components lie very low in the chassis, providing a lower center of gravity, resulting in excellent traction and stability.
The Five Types of Subaru Symmetrical All-Wheel Drive:
Subaru currently uses five different types of Symmetrical AWD. Each is specific to the Subaru model and transmission.The five types are:
■ Continuous All-Wheel Drive
■ Active All-Wheel Drive
■ Variable Torque Distribution (VTD) All-Wheel Drive.
■ Driver Controlled Center Differential (DCCD) All-Wheel Drive
■ Vehicle Dynamics Control (VDC) All-Wheel Drive