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.
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
The Environmental Protection Agency (EPA) now has regulations in place that establish requirements for on-board diagnostic (OBD-II) systems on light-duty vehicles and light-duty trucks. The purpose of the OBD-II system is to ensure proper emission control system operation for the vehicle’s lifetime by monitoring emission-related components and systems for deterioration and malfunction.
There’s a big difference between detecting only hard faults (OBD-I) and having the ability to actively monitor the system for proper operation, deterioration or a malfunction (OBD-II).
Engines in today’s vehicles are largely electronically controlled. Sensors and actuators sense the operation of specific components (e.g., the oxygen sensor) and actuate others (e.g., the fuel injectors) to maintain optimal engine control. An on-board computer, known as the “powertrain control module,” controls all of these systems.
For those of you who are interested, this is how Subaru breaks down a part number. This could help you guess a part number if one that you found on a part is missing digits or is damaged.
Genuine Part Classification Codes
A = Part Description Code
B = Part Sequential Code
C = Part Category Code
D = Specific Code
E = Modification Code
F = Color Code
Description of Genuine Part Classification Codes
A. Part Description Code: Identifies part name and function. If the first position is an alpha, it identifies an accessory.
B. Part Sequential Code: Sequential number system assigned to the part number by Fuji Engineering Division.
C. Part Category Code: Key position of the part number in determining the logic of the numbering system:
A = Engine and Transmission Parts
K = Engine and Transmission Parts
X = Some Automatic Transmission Parts
G = Body Parts
D. Specific Parts: Identifies specific characteristics of parts with the same part description code and designated sequences from A00. The specific code is assigned by the Fuji Engineering Division for internal use only.
E. Modification Code: Identifies an engineering change to the part. For example:
0 = original
1 = 1st modification
2 = 2nd modification
3 = 3rd modification
F. Part Color Code: Identifies color coded parts for digits 11 and 12. Digit 11 = color and digit 12 = degree.
Code E or F in the 12th digit is for Fuji Heavy Industries (FHI) internal purposes only.
Since 1996, original equipment manufacturers have been using R-134a in all automotive air conditioning systems. R-134a is now the refrigerant of choice. This short article will help you learn proper safety procedures regarding the use of R-134a. Also, to stress the importance of refrigerant identification for OEM automotive A/C systems, we will explain some of the specific system component changes, and discuss important changes to A/C service equipment.
You may already be familiar with R-134a, A/C retrofits, and proper procedures. If you are confident of your abilities and retrofit knowledge, try answering the 20 question quiz that ends this article. If you are not sure about your R-134a retrofit knowledge, read this article first.
What Is R-134a?
R-134a does not contain suspected ozone-depleting chlorofluorocarbons. The chemical compounds and molecular structures of the old refrigerant R-12 and the new refrigerant R-134a are completely different. However, the temperature/pressure relationships of the two are very similar. Automotive publications, equipment manufacturers, and refrigerant suppliers, provide technical specifications and properties for R-134a.
R-134a and R-12 are not compatible. Under no circumstances should they be mixed. Vehicle and service manufacturers have gone to great lengths to prevent cross-charging or contamination of these two refrigerants. For instance, R-12 systems use a small high-side service port, and a large low-side service port. R-134a service fittings are completely different. The high side service port is now the larger of the two. These quick disconnect fittings will not work with R-12 service equipment.