a friend of mine has a 90 legacy. he is getting a code for the duty solonoid b. the power light flashes everytime its started. the car runs great. what does this do and where do we start looking.

Duty b is for torque converter lock-up. Here's some cut and paste from and endwrench.com article:

 

Lock-Up Torque Converter

The torque converter is designed to match a wide range of engines from large to small displacement. It is also designed to improve acceleration from a stop and reduce fuel consumption.

 

The torque converter has an electronically controlled, hydraulic lock-up clutch system that prevents slip loss during medium to high speed operation. This system replaces the previous centrifugal lock-up type clutch.

 

There is a friction surface on the back of the lock-up clutch (piston) which locks against the back of the impeller housing.

 

Clutch engagement shock is minimized in part, because of the torsional clutch dampers and the wave spring/friction washer combination.

 

The lock-up operation is controlled by the TCU which then regulates Duty Solenoid “B” mounted on the lower valve body. This solenoid controls the lock-up valve located in the transmission upper valve body. Finally, the lock-up valve activates the lock-up clutch (piston) located in the torque converter.

Operating Modes

The TCU regulates the cycle of Duty Solenoid “B.” When the duty solenoid operates at five percent duty, i.e., substantially more “OFF” than “ON,” pilot pressure is directed to the lock-up control valve.

 

In this condition, the control valve is pushed UPWARD by the combined pilot pressure and spring force. This allows regulated hydraulic pressure to enter the

 

The release pressure then pushes the lock-up clutch (piston) rearward and the lock-up clutch is released from the impeller cover. On the other hand, oil drains through the apply circuit to the oil cooler in the radiator.

 

When Duty Solenoid “B” operates at 95 percent duty, i.e., substantially more “ON” than “OFF,” it reduces pilot pressure to the control valve. In this condition, the control valve is pushed DOWNWARD due to the reduced pilot pressure. As a result, regulated hydraulic pressure is directed to the lock-up apply circuit and the release circuit drains.

 

The apply pressure then pushes the lock-up clutch (piston) forward which engages the lock-up clutch with the impeller cover. When engaged, the transmission is coupled directly to the engine.

where's a good place to start looking. or will it be ok like it is for a while

where's a good place to start looking. or will it be ok like it is for a while

the duty b solenoid is inside the trans and generally is not considered to be user friendly. but more experienced 'users' may have a different opinion.

 

your gas mileage will suffer but i don't think driving it will be harmful. you didn't say how many miles are on the car. my guess, is you are looking at a used trans.

 

some one has posted a link to some FSM downloads which include several pages of diagrams for the auto trans. probably not your year, but good generic info just the same.

 

try searching FSM trans*.

 

i found this: http://www.subaru-svx.net/photos/files/lee/18575.pdf

look at item #6 on page 21 of 27.

this is for a SVX but still good info.