Subaru steering systems
Contents
1. Rack And Pinion Steering Mechanism Subaru steering systems utilize a rack and pinion steering mechanism As the pinion gear rotates the rack moves left or right Rack and pinion steering gives the driver precise control over the wheels The simple compact design is easy to service CGR VGR Ratios Sa Two manual steering racks are used in Subaru vehicles a constant gear ratio CGR rack Beek ANE SCR SOTO and a variable gear ratio VGR rack The teeth on the CGR rack are equally spaced so the Mechanism A g turning effort is equal throughout the turning range The teeth on the VGR rack are spaced closer together on the ends of the rack than in the middle The turning effort decreases as the turning angle increases so sharp radius turns are easier to make Legacy and SVX Steering Racks Several different power steering racks have been installed in Subaru vehicles The racks used in the L series XT Legacy and SVX vehicles are similar All have a one piece gearbox and lack the external air vent distribution tube found on the rack in pre 85 and carryover vehicles However the XT rack differs from the L series rack in several ways The XT rack is CGR VGR Ratios made of aluminum and has a different control valve Different types of hydraulic seals are used in the two racks and each has its own unique special service tool The power steering rack in the pre 85 model year vehicles and the Brat has a two piece gearbox and an air vent dist2. The Signal Controller grounds the heater relay which passes battery voltage to the heater The heater relay is located near the motor pump assembly Note The Heater only works when the thermistor signals an extreme cold condition Steering Sensor Assembly The Steering Sensor sends a steering frequency signal to the Signal Controller The Steering Sensor consists of two components e Photo coupler e Sensor Plate with 60 slits As the sensor plate passes through the photo coupler it generates a pulse signal which is interpreted as steering frequency A 360 degree turn equals 60 pulses Four 90 degree move ments also equal 60 pulses Note The Signal Controller determines the difference between one full 360 degree rotation of the steering wheel and four quarter 90 degree turns based upon vehicle speed Signal Controller The Signal Controller receives inputs primarily from the vehicle speed sensor and the steering sensor It continuously monitors the driving conditions over any given 20 second time period Based upon an average of the vehicle speed and the steering frequency it then determines the amount of power assist duty ratio required This signal is then sent to the Power Controller which in turn operates the motor Power Controller The Power Controller is the last major Cybrid steering component It functions like a duty solenoid in order to control the electric current to the Motor Pump assembly The power controller r
3. solenoid circuit open 3 Vehicle speed sensor fault 4 Memory back up circuit fault 5 Engine speed signal fault Constant Flashing System okay Note Always refer to the appropriate model year service manual Section 4 3 troubleshooting procedure section when performing self diagnosis Notes and Cautions Steering Column Removal Always refer to the appropriate model year Subaru Service Manual and follow the proce dure for removal of the SRS Airbag Module prior to any repair and servicing or removal of the steering wheel and steering column from all airbag equipped Subaru vehicles Always disconnect the U bolts before loosening the column mounting bolts Disconnect the wiring harness connectors before removing the column Remove the XT column carefully to avoid damaging the meter and instrument panel Steering Gearbox Overhaul e Do not crimp the pipes e Do not scratch the rack or the cylinder e Do not clog the air passages with grease e Coat the seal and bushings with ATF fluid before installing them e Install the seals with their lips toward the pressure area e Use the correct special tools Airbag Steering Column Installation Review the roll connector phasing procedures listed in the appropriate model year service manual Section 4 3 The roll connector must be phased to the steering system only when the front wheels are centered Align the inner center indicator on the rotating cover next to window
4. ature was added to the 85 and later model year L series tilt steer ing column On 85 and 86 model year vehicles depressing a button on the left side of the steering column releases the tilt shaft The tilt shaft on 87 model year vehicles is released by pulling forward a knob located on the left side of the column Spring action lifts the column to its highest position When the column is pulled down a lock pin slips into a hole in the memory bracket securing the column in its previous position The Legacy and SVX memory function is controlled by disengaging a movable gear from a stationary gear This causes the coil springs to tilt the steering column up A mem ory gear is engaged with the movable gear A plate united with the memory gear is inter posed between the movable and stationary gears When the steering wheel is pushed down the movable gear is disengaged from the plate which allows the stationary gear and the memory gear to return to the original position XT Steering Column The XT steering column has tilt and pop up features as well as a telescopic feature A telescopic lever on the end of the steering column when rotated counterclockwise moves a lock key away from the steering shaft This allows the control wing and the steering wheel to be moved in or out in an axial direction The maximum telescoping stroke is 40 mm 1 57 in Power Steering System The operation of the tilt feature and pop up feature on the XT steerin
5. cing the steering gearbox For detailed instructions on steering rack overhaul refer to the appropriate model year service manual Dept Whi ed Clears Airbag Steering Column Installation Precautions Fe os e Reference all airbag equipped vehicles e Review the roll connector phasing procedures listed in the appropriate model year service manual Section 4 3 e The roll connector must be phased to the steering system only when the front wheels are centered e Align the inner center indicator on the rotating cover next to window with the arrow on the connector case e Complete the following alignment adjustments when the inner indicator in the window shows 1R rotate cover one full rotation to the right 2R rotate cover two rotations to the right 1L rotate cover one full rotation to the left 2L rotate cover two rotations to the left e Use the guide pins to align the roll connector with the steering wheel Motor and Pump Assembly Cybrid Power Steering The Cybrid Power Steering System was standard equipment on the XT6 It s a computer controlled electric motor driven hydraulic steering system using a power assisted rack and pinion assembly similar to the XT This system provides improved steering feel and more precise power assist over a wider operating range Fuel consumption is reduced because it requires less horsepower due to the electrically driven hydraulic pump The specific system used on t
6. e MPFI XT XT6 60 75 kg cm 853 1067 psi If Yes Legacy 75 80 kg cm 1067 1138 psi e System Okay ka SVX 78 85 kg cm 1109 1209 psi Pi Steering Syst feet eee Servicing The Steering System Note Always refer to the appropriate model year Subaru Service Manual and follow the pro cedure for removal of the SRS airbag module prior to any repair and servicing or removal of the steering wheel and steering column from all airbag equipped Subaru vehicles iid Wrench SUBARU Column Removal Precautions e Reference service manual Section 4 3 for rigid column and tilt column servicing procedures e Always disconnect the U bolt joint before loosening the column mounting bolts e Disconnect the wiring harness connectors before removing column e Install a 8 mm x 16 mm lock bolt to secure XT column e Remove the XT column carefully to avoid damaging meter and instrument panel e For proper steering wheel alignment center the front wheels and scribe an alignment mark between the steering wheel hub and the shaft prior to disassembly When removing the steering column always observe the precautions listed above Gearbox Servicing Precautions Do Not e Crimp the pipes Scratch the rack or cylinder Clog the air passages Do e Lubricate the seals bushings e Install the seal lips toward the pressure area Airbag Steering Column e Use the correct special tools Procedures Follow the above precautions when servi
7. egulates the ground circuit of the motor based upon input from the Signal Controller A 100 percent duty equals maximum assist Operation The Signal Controller selects one of four driving modes based on vehicle operation e High Speed Driving e Suburban Driving e Winding Road Driving e City Driving High speed driving requires the least amount of power assist As the vehicle speed increases the power assist decreases During suburban driving the vehicle speed is slower but the steering input is usually more frequent In this mode of operation the power assist generally increases For winding road driving the speed varies but it is generally moderate In this case the steering input is frequent and the power assist is close to maximum City driving is character ized by its low speed and frequent steering inputs In this case assist is at or near maximum When the steering input stops the power assist gradually decreases Operating Conditions Above 6 MPH The driving mode is determined by the steering frequency and the vehicle speed The signal controller then selects a driving mode and determines an appropriate duty ratio for that mode When the driving mode changes the duty ratio is altered gradually approximately 2 5 per cent every 0 1 second This provides a smooth transition from one steering mode to another which prevents possible feedback to the steering wheel Operating Conditions Below 6 MPH When there is NO steering input
8. fault diagnosis procedures SVX Engine Speed and Vehicle Speed Sensitive Steering Systems There are two model specific systems available on SVX vehicles e The engine speed sensitive or conventional belt driven hydraulic pump and pinion type steering system is standard equipment on the SVX e An SVX equipped with the Touring Package uses an optional vehicle speed sensitive system This system provides normal power assist at low vehicle speeds for reduced driver steering effort and reduced steering assist at increased vehicle speeds for increased road feel and improved engine operating efficiency Both systems have many similarities with the Legacy system Power Steering Pump Both systems share many similarities to existing Subaru steering systems Both use a belt driven power steering pump although the pump housings are different in appearance Rack A conventional power assisted rack with the standard Subaru lines and hoses is used by the standard system Oil Cooler An oil cooler pipe has been added to both SVX systems It is located in front of the radiator on the return side of the system Rubber Coupler A steering shaft rubber coupler is used by both SVX systems to reduce road noise and vibration amp Subaru Steering Systems Soleniod Pinion Assembly Reaction Mechanism Vehicle Speed Sensitive Steering Power Steering Pressure Switch A power steering pressure switch is loca
9. g column is similar to that of the L series tilt steering column Moving the tilt lever down releases the steering column The rubber bushing in the toe board deflects to allow the column to pivot around the universal joint between the column and the gearbox The dash also tilts up and down with the steering column XT Pop up Mechanism The XT pop up feature is operated by pulling a knob located on the instrument panel lower left side of the instrument panel A cable connects the knob to the lockpin Pulling the knob retracts the lockpin from the column bracket allowing the spring to force the Oil Pump Operation column upward When the column is pulled down it locks in its original position Power Steering Rack System Subaru s power steering system contains a pump hydraulic line and a gearbox rack The hydraulic pump is a vane type pump driven by the engine It provides pressurized fluid for the system Oil Pump Operation The pump has two internal valves a flow control valve and a relief valve The flow control valve regulates the volume of power steering fluid delivered to the rack During Flow Control Valve Operation high engine rpm the pressure in the pump overcomes the flow control valve spring The control valve slides back to close off an oil passage to the rack and to open an oil return port to the pump inlet This reduces the power assist to the rack during high speeds improving the steering wheel feel and response Rel
10. he XT6 is quicker than other XT power steering systems with just 3 2 turns lock to lock Cybrid Steering Components Heater The Cybrid Power Steering System consists of four major components The Motor and Pump assembly mounted on the front bulkhead firewall e A Steering Sensor located inside the vehicle at the base of the steering column e A Signal Controller located in the left rear quarter panel e The Power Controller mounted on the front bulkhead firewall to the left of the Motor Pump assembly Motor Pump Assembly The Motor Pump assembly is similar to a starter motor since it has an armature fields Steering Sensor Assembly and brushes which are serviceable The electric motor drives a pump which is very similar in design to an engine driven pump This combination replaces the familiar belt driven P S pump assembly The Cybrid System requires special hydraulic fluid to retain stable viscosity during cold temperatures a Efid Wrench Subaru Steering Systems Signal Controller Power Steering Pump Steering Rack Heater The Pump incorporates an electric heater to warm the hydraulic fluid in extremely cold operating conditions improving the steering performance A thermistor type switch located on a bracket above the Motor Pump assembly senses the underhood ambient temperature and sends an input to the Signal Controller The Heater operates for approximately five minutes after engine start up
11. ief Valve Operation Pressure in the system is also controlled by the relief valve built into the flow control valve The relief valve consists of a ball valve and a relief spring When hydraulic pres sure in the system reaches a specified value the ball valve opens so that part of the working fluid flows into the return port via the fixed orifice Relief Valve Operation Power Steering Rack The gearbox consists of a control valve and a power cylinder A power piston attached to the rack divides the cylinder into two chambers As fluid is directed by the control valve to either side of the piston the rack is pushed in the same direction in which the steering wheel is being turned Control Valve Operation Hydraulic fluid supplied to the rack is controlled by the rotary control valve As part of the pinion gear shaft the control valve directs fluid flow to one side or the other of the Power Steering Rack power piston When steering effort is not applied to the pinion shaft hydraulic pressure in the valve and to both pressure chambers is held equal Oil is directed from the center of the valve back to the pump As steering effort is applied a torsion bar in the valve deflects in proportion to the resistance encountered Fluid is allowed to pass directly from the pump discharge side to Subaru Steering Systems the pressure chamber creating a pressure differential between the two chambers This hydraulic imbalance causes the p
12. ing temperature before performing the test Keep the following precautions in mind as well e Do not leave the pressure gauge valve closed for more than five seconds doing so may damage the pump Doe e Do not hold the steering wheel in the full lock position for longer than five seconds this Steering Effort Applied may damage the pump Keep the engine speed at idle e Handle power steering fluid carefully catch spilled fluid with shop cloths to prevent damage to the vehicle s finish Power Steering Pressure Test Attach pressure gauge 925711000 adapter A 926210000 and adapter B 926220000 to the discharge part of the pump then perform the three pressure tests listed below Senna System Step 1 Regular pressure Deepen ogee Engine idling valve open If No 142 psi 10 kg cm2 or less e Crimped Fluid line Replace e Leaking fluid line Tighten or replace e Clogged fluid line Drain or replace Step 2 Relief pressure Engine idling valve closed If No L series Loyale SPFI 40 55 kg cm2 569 782 psi Faulty relief valve XT XT6 60 75 kg cm 853 1067 psi e Oil pump leak Oil Leak Points Legacy 75 80 kg cm 1067 1138 psi e Worn pump SVX 78 85 kg cm 1109 1209 psi In all cases replace pump Step 3 Working Pressure E Engine idling valve open If No E steering wheel turned stop to stop e Faulty control valve Replace i tii L series Loyale SPFI 40 55 kg cm 569 782 psi s k Loyal
13. iston and rack to move to one side Piston movement causes fluid in the low pressure chamber to return to the pump through the control valve The more the torsion bar deflects the greater the pressure differential becomes The increased pressure assists in the turning effort Steering System Troubleshooting Steering performance symptoms may be the result of a number of problems The cause of the problem could be inside or outside of the steering system For example heavy or hard steering could be a result of a malfunctioning pump of low idle speed of a defective control valve or of tires not properly inflated When diagnosing the cause of a steering problem care fully follow the troubleshooting charts given in the appropriate model year service manual Oil Leak Points Leaks in the gearbox should be confirmed before removing the gearbox from the vehicle If leakage is suspected clean the suspected portion and turn the steering wheel from lock c to lock approximately 30 or 40 times with the engine running slowly to verify the leakage ontrol Valve Operation A f No Steering Effort Refer to the service manual for the correct repair procedures Power Steering System Pressure Testing If the troubleshooting procedures lead you to suspect a fault in the power steering system perform a pressure test The vehicle must be equipped with the specified tires and rims and the tires must be properly inflated Then bring the engine up to operat
14. onger and low fluid pressure is supplied to the pinion reaction chamber More assist pressure is supplied to the system to reduce driver steering effort Conversely a low duty ratio means a shorter solenoid activation period and high fluid pressure is provided to the pinion reaction chamber Less assist pressure is supplied to the system increasing the driver steering effort When there is zero duty ratio such as a disconnected solenoid harness maximum pressure is supplied to the pinion reaction chamber This results in minimum assist pressure to the system and maximum driver steering effort Reaction Mechanism Components Operation The pinion assembly functions similar to previous Subaru systems with the addition of a reaction mechanism located between the brackets The reaction mechanism components are e Reaction piston assembly e Pinion output shaft and torsion bar e Steel balls e Pinion input shaft with rotary valve During normal operation such as straight ahead driving the duty ratio is low and the pressure to the reaction piston is high The piston holds the steel balls in the grooves of the input shaft reaction arm allowing for less torsional twist of the torsion bar This decreases the pressure flow to the system which decreases the power assist to increase driver steering effort A high duty ratio during low vehicle speeds provides low pressure to the reaction piston The piston allows the steel balls to move in the groove
15. ribution tube It also has seals service procedures and special service tools that differ from the other racks Rigid Steering Column 7 Three types of steering columns are used in Subaru vehicles a rigid steering column a tilt steering column and the XT and SVX tilt and telescoping steering column The rigid steering column is found on L series DL models the Legacy standard model and Justy vehicles The Legacy and SVX Steering rigid steering shaft does not tilt or pop up but is collapsible a safety feature The shaft is Racks connected to the gearbox by universal joints Tilt Steering Column The tilt steering column is found on late model L series GL Loyale Legacy and SVX vehicles The tilt steering column features both tilt and pop up operations It is divided into two sections upper and lower connected by a universal joint The L series uses a friction type lock By pushing down on the tilt lever tension on a bolt is released and the steering column may be tilted to an infinite number of positions Pre 85 model year tilt steering columns could be tilted to only eight positions When the tilt lever is returned the bolt tightens to lock the steering column in position The Legacy and SVX use a gear type lock The Lift Up lever tilts the steering column all the way up The Tilt Pull lever tilts the steering column to the optimum driving position Tilt Steering Column SUBARU A pop up memory fe
16. s of the input shaft reaction arm This allows more torsional twist of the torsion bar which increases the pressure flow to the system and increases power assist to decrease driver steering effort Failsafe operation is dependent upon the type of failure i e the reaction solenoid sensor signal failure or steering system ECU The control unit discontinues the duty signal to the reaction solenoid This results in high reaction chamber pressure and the power assist is fixed at the minimum level Test Connectors The system has three diagnostic modes D Check e Read Memory e Clear Memory The trouble codes are displayed by the STEERING light Subaru Steering Systems To access the D Check mode e Connect a ground wire to the test mode connector terminal 5 then start the engine e Move the vehicle at least 31 feet and then remove the ground wire from terminal 5 e Read the codes emitted by the steering system warning lamp To access Read Memory e Connect the ground wire to test mode connector terminal 6 e Start the engine and then remove the ground wire from terminal 6 e Read the codes emitted by the steering system warning lamp To Clear Memory e Turn the ignition switch off e Connect a jumper wire to terminal 5 and 6 e Start the engine and remove the jumper wire from terminal 5 and 6 Confirm that the memory is clear Trouble Codes The diagnostic trouble codes are 1 Reaction solenoid circuit shorted 2 Reaction
17. ted on the outlet side of the pump The switch monitors increased engine load during idle speed steering The switch provides an input to the MPFI ECU which prevents stalling by raising the engine idle speed There is not an addi tional trouble code for the MPFI ECU Vehicle Speed Sensitive Power Assisted Steering Optional System Main components unique to this system are e Power steering control unit e Reaction duty solenoid valve e Vehicle speed sensor speedometer system Modified pinion assembly Steering System Diagram The steering system ECU receives input from the engine speed sensor through the MPFI ECU and the transmission vehicle speed sensor The ignition switch provides power for the system while the battery provides power for the memory The diagnostic test mode connec tors are also an input to the control unit The control unit sends signals to the reaction control solenoid valve located on the pinion assembly housing and to the steering system warning lamp located on the dash to the left of the steering wheel Solenoid Pinion Assembly The reaction solenoid valve controls the amount of hydraulic power assist to the rack The valve is mounted to the pinion housing The valve is controlled by the steering system ECU output signal based upon vehicle and engine speed input to the ECU The solenoid valve functions on a duty ratio to control the power assist A high duty ratio means the solenoid activation period is l
18. the duty ratio is zero percent no assist However with any steering input the duty ratio immediately increases to 100 percent maximum assist The sub fan turns off if it was on but turns back on again when the steering input ceases With continued steering input the duty ratio remains at 100 percent unless the vehicle speed exceeds 6 MPH When the steering input ceases the duty ratio reduces approximately 2 5 percent every 0 5 second This prevents possible feedback to the steering wheel Subaru Steering Systems Oil Cooler Power Steering Pressure Switch Steering Components l amp Service Procedures Motor and Pump Alignment The pump assembly is serviced similar to the belt driven pump on the H 4 engine The electric motor has serviceable brushes similar to those in a starter motor Note This system uses special hydraulic fluid DEXRON II may be substituted in an emergency Flush and replace with IDEMITSU fluid as soon as possible Note The pump should be indexed as shown in order to facilitate proper reassembly Note Detailed trouble shooting and service procedures can be found in Section 4 3 of the service manual Self Diagnostics and Failsafe In the user mode the driver is notified by the STEERING light whenever a system malfunc tion occurs in e The Signal Controller e The Power Controller e The Signal System Sensors e The Power Source for the pump motor Note This is a highly reliable steering s
19. with the arrow on the connector case Complete the following alignment adjustments when the inner indicator in the window shows e 1R rotate cover one full rotation to the right e 2R rotate cover two rotations to the right e 1L rotate cover one full rotation to the left e 2L rotate cover two rotations to the left Use the guide pins to align the roll connector with the steering wheel The SVX tie rod dust boots require special servicing procedures because the rack tie rod dust boots are one time use only Cut the small end of boot to remove the boot Always replace the boot if removed The boot uses a wire tie on the large end of the boot The left side pinion side tie rod has a groove next to the boot clamp groove The right side does not have a groove Efid Wrench
20. ystem However should an electrical component malfunction it will always fail safe for limp home Fail Safe Results If the pump motor current exceeded 100 Amps for 10 or more seconds power assist will cease The STEERING light will come on and the duty ratio will be reduced to 0 percent However full manual control will allow the vehicle to be safely driven If the vehicle voltage drops below 9 volts there will be partial power assist The STEERING light will come on and the duty ratio will be gradually reduced Should the voltage recover the duty ratio will return to normal and the steering light will go off If the engine stalls the STEERING light will come on and the duty ratio will be gradually reduced This allows power assist for several seconds Once the engine is restarted however the STEERING light goes off and the power assist returns as needed Should there be a loss of the speed sensor signal Above 15 MPH the STEERING light will come on and the duty ratio will be maintained at the previously set level Note Prior to any servicing or fault diagnosis confirm that the vehicle has had MPS controller set PIN 31186GA070 installed For additional details refer to Campaign Bulletin WZM 48 For vehicles which have had this replacement procedure performed refer to MSA5T9212A XT6 Electronic Controlled Motor Drive Power Steering Service Manual Supplement and the appropri ate model year Service Manual Section 4 3 for D Check and
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