Power Steering System: Other Chevrolet Silverado 1500

Data Display

The scan tools input display function can be helpful in determining if the EHPS module is receiving the correct input status. This can assist in determining if the EHPS system is actually receiving ignition 1 voltage.

Cycle Outputs

A scan tool may be used in order to command the EHPS pump speed enable message ON or OFF. This can be very helpful in determining if a certain portion of a circuit or a component is in working order. The following tests are available under the Special Functions selection. The following can be commanded ON or OFF

1. EHPS pump speed
2. BPP sensor minimum position learn

Electro-Hydraulic Power Steering (EHPS) Scan Tool Data List

Steering Effort Hard in One or Both Directions

Steering Effort Hard in One or Both Directions

Steering Effort Too Easy in One or Both Directions

Steering Effort Too Easy in One or Both Directions

Scheme 92

1. Remove the BPP sensor bolt (1).
2. Remove the BPP sensor (2) from the mounting bracket.
3. Disconnect the BPP sensor electrical connector (1).
4. Remove the BPP sensor (2) from the vehicle.

Scheme 93

1. Connect the BPP sensor (2) electrical connector (1).
2. Align the BPP sensor (1) with the actuation arm (2) on the brake pedal and the BPP sensor mounting bracket.
3. Install a new 4 mm bolt (1), with LOCTITE™, to the BPP sensor. Tighten: Tighten the bolt to 9 N.m (80 lb in).
4. Calibrate the BPP sensor. Refer to «Brake Pedal Position Sensor Calibration Description and Operation»(ref-238245-S08553498542006072400000) .

Tools Required

1. J 35555 Metal Mityvac. See «Special Tools»(ref-238245-S22550396302006072400000) .
2. J 43485 Power Steering Bleeder Adapter. See «Special Tools»(ref-238245-S22550396302006072400000) .

Scheme 94

Scheme 95

1. Verify that the hoses do not touch any other part of the vehicle.
2. Verify that all hose connections are tight.
3. Remove the pump reservoir cap.
4. Fill the pump reservoir with fluid to the FULL COLD level.
5. Attach the J 43485 to the J 35555 or equivalent. See «Special Tools»(ref-238245-S22550396302006072400000) .
6. Place the J 43485 on or in the pump reservoir filler neck. See «Special Tools»(ref-238245-S22550396302006072400000) .
7. Apply a vacuum of 68 kPa (20 in Hg) maximum.
8. Wait 5 minutes. Typical vacuum drop is 7-10 kPa (2-3 in Hg). If the vacuum does not remain steady, refer to Excessive Vacuum Drop Diagnosis at the end of this procedure.
9. Remove the J 43485 and the J 35555 . See «Special Tools»(ref-238245-S22550396302006072400000) .
10. Reinstall the pump reservoir cap.
11. Start the engine. Allow the engine to idle.
12. Turn off the engine.
13. Verify the fluid level. Repeat steps 11-13 until the fluid stabilizes.
14. Start the engine. Allow the engine to idle.
15. Turn the steering wheel 180-360 degrees in both directions 5 times.
16. Switch the ignition off.
17. Verify the fluid level.
18. Remove the pump reservoir cap.
19. Attach the J 43485 to the J 35555 or equivalent. See «Special Tools»(ref-238245-S22550396302006072400000) .
20. Place the J 43485 on or in the pump reservoir filler neck. See «Special Tools»(ref-238245-S22550396302006072400000) .
21. Apply a vacuum of 68 kPa (20 in Hg) maximum.
22. Wait 5 minutes.
23. Remove the J 43485 and the J 35555 . See «Special Tools»(ref-238245-S22550396302006072400000) .
24. Verify the fluid level.
25. Reinstall the pump reservoir cap.

Scheme 96

1. If the vacuum continues to drop, remove the pressure and return hose from the pump.
2. Install the plugs (1,2) supplied with the J 43485 into the pressure and return port. See «Special Tools»(ref-238245-S22550396302006072400000) .
3. Attach the J 43485 to the J 35555 or equivalent. See «Special Tools»(ref-238245-S22550396302006072400000) .
4. Place the J 43485 on or in the pump reservoir filler neck. See «Special Tools»(ref-238245-S22550396302006072400000) .
5. Apply a vacuum of 68 kPa (20 in Hg) maximum.
6. If the vacuum drops again, repair or replace the pump. If the vacuum holds steady, continue to check the other parts of the steering system.
7. Observe the fluid.
8. If condition persists, replace the following parts: The return hose clamps The return hose O-rings The pressure hose O-rings The gear cylinder line O-rings The reservoir to pump O-ring
9. Repeat the bleed procedure from the beginning.
10. Drive the vehicle approximately 16 km (10 mi) in order to warm the system to operating temperature. Evaluate vehicle on a smooth flat surface.
11. Verify the following conditions: There is smooth power assist. The vehicle operates quietly. The pump maintains the proper fluid level. There is not any leaking in the steering system. The fluid is free of foam or discoloration.

Tools Required

J 24319-01 Universal Steering Linkage Puller. See Special Tools .

J 22610 Service Boot Clamp Installer. See Special Tools .

Scheme 97

1. Raise the vehicle. Support the vehicle with suitable safety stands. Refer to «Lifting and Jacking the Vehicle»(ref-238215-S26215505352006072400000) in General Information.
2. Remove the outer tie rod. Refer to «Rack and Pinion Outer Tie Rod End Replacement»(ref-238245-S13280589462006072400000) .
3. Remove the hexagon jam nut (2) from the inner tie rod assembly (1).
4. Remove the tie rod end clamp (2) from the rack and pinion boot (1).
5. Remove the boot clamp (1) from the rack and pinion boot with side cutters.
6. Discard the boot clamp (1).
7. Remove the rack and pinion boot (1) and the breather tube from the rack and pinion gear assembly.

Scheme 98

1. Prior to the rack and pinion boot installation, apply grease to the inner tie rod assembly (2) and the rack and pinion gear assembly (1).
2. Install the rack and pinion boot (3) onto the inner tie rod assembly (2).
3. Install the breather tube while aligning the breather tube with the mark made during removal and the molded nipple of the rack and pinion boot.
4. Install the rack and pinion boot onto the gear assembly (1) until the rack and pinion boot (3) is seated in the gear assembly groove.
5. Install the boot clamp (1) on the rack and pinion boot (2).
6. Crimp the boot clamp (1) using the J 22610 . See «Special Tools»(ref-238245-S22550396302006072400000) .
7. Pinch the pliers together on the rack and pinion boot (2) in order to install the tie rod end clamp.
8. Install the new boot clamp (2) onto the rack and pinion boot (1).
9. Install the hexagon jam nut (2) to the inner tie rod assembly (1).
10. Install the outer tie rod. Refer to «Rack and Pinion Outer Tie Rod End Replacement»(ref-238245-S13280589462006072400000) .
11. Check the wheel alignment. Refer to «Measuring Wheel Alignment»(ref-238306-S31266173742006072400000) in Wheel Alignment.

Scheme 99

1. Remove the front grille. Refer to «Grille Replacement (GMC)»(ref-238209-S09461896312006072400000) or «Grille Replacement (Chevrolet)»(ref-238209-S06007732772006072400000) in Exterior Trim.
2. Place a drain pan under the vehicle.
3. Siphon the fluid from the reservoir to prevent excess spillage.
4. Remove the clamp retaining the power steering cooler inlet hose (3) to the power steering gear (2).
5. Remove the clamp retaining power steering cooler outlet hose (5) to the power steering pump (1).
6. Remove the bolts (2) retaining the power steering cooler from the radiator support.
7. Remove the power steering cooler from the vehicle.

J 22610 Keystone Clamp Pliers. See Special Tools .

Scheme 100

Scheme 101

1. To remove the outer tie rod. Refer to «Rack and Pinion Outer Tie Rod End Replacement»(ref-238245-S13280589462006072400000) .
2. Remove the hexagon jam nut (2) from the inner tie rod assembly (1).
3. Remove the tie rod end clamp (2) from the rack and pinion boot (1).
4. Remove the boot clamp (1) from the rack and pinion boot with side cutters.
5. Discard the boot clamp (1).
6. Remove the rack and pinion boot (1) and the breather tube, if present, from the rack and pinion gear assembly.

Scheme 102

Scheme 103

1. Install the new boot clamp (1) onto the rack and pinion boot (3).
2. Prior to rack and pinion boot installation, apply grease to the inner tie rod assembly (2) and the rack and pinion gear assembly (1).
3. Install the rack and pinion boot (3) onto the inner tie rod assembly (2).
4. If present, install the breather tube while aligning the breather tube with the mark made during removal and the molded nipple of the rack and pinion boot.
5. Install the rack and pinion boot onto the gear assembly (1) until the rack and pinion boot (3) is seated in the gear assembly groove.
6. Install the boot clamp (1) on the rack and pinion boot (2) with J 22610 . See «Special Tools»(ref-238245-S22550396302006072400000) .
7. Crimp the boot clamp (1).
8. Pinch the pliers together on the rack and pinion boot (2) in order to install the tie rod end clamp.
9. Install the tie rod end clamp (2) onto the rack and pinion boot (1).
10. Install the hexagon jam nut (2) to the inner tie rod assembly (1).
11. To assemble the outer tie rod assembly. Refer to «Rack and Pinion Outer Tie Rod End Replacement»(ref-238245-S13280589462006072400000) .

J 34028 Inner Tie Rod Wrench. See Special Tools .

Scheme 104

Scheme 105

1. To remove the rack and pinion boot, refer to «Rack and Pinion Boot and Breather Tube Replacement - Off Vehicle»(ref-238245-S01618047252006072400000) .
2. Place the gear in a vise.
3. Remove the shock dampener (6) from the inner tie rod housing (4).
4. Slide the shock dampener (6) back on the rack (5).
5. Place a pipe wrench on the rack (5) next to the inner tie rod housing (4).
6. Place a wrench on the flats of the inner tie rod housing (4).
7. Rotate the inner tie rod housing (4) counterclockwise, while holding the rack stationary, until the inner tie rod separates from the rack (5).
8. Remove the shock dampener (3) from the inner tie rod housing (2).
9. Slide the shock dampener (3) back on the rack (5).
10. Place a pipe wrench on the rack.
11. Place a wrench on the flats of the inner tie rod housing (2).
12. Rotate the inner tie rod housing (2) counterclockwise, while holding the rack stationary, until the inner tie rod (1) separates from the rack (5).
13. If female rack (1) and male inner tie rod (3), remove the old LOCTITE® from the threads (2) of the inner tie rod (3) and the rack (1). If male rack (5) and female inner tie rod (4) LOCTITE® will not be present.

Scheme 106

Scheme 107

Scheme 108

Scheme 109

1. Slide the shock dampener (4) forward onto the rack (3).
2. If female rack (3) and male inner tie rod (2), apply LOCTITE® 262, or equivalent, to the inner tie rod threads.
3. Attach the inner tie rod onto the rack (3).
4. Place a pipe wrench on the rack (3) next to the inner tie rod housing (2).
5. Place a torque wrench and J 34028 on the flats of the inner tie rod housing (2). See «Special Tools»(ref-238245-S22550396302006072400000) . Tighten: Tighten the inner tie rod to 100 N.m (74 lb ft).
6. Slide the shock dampener (2) forward onto the rack.
7. If female rack and male inner tie rod (1), apply LOCTITE® 262, or equivalent, to the inner tie rod threads.
8. Attach the inner tie rod (1) onto the rack.
9. Place a pipe wrench on the rack next to the inner tie rod housing (4).
10. Place a torque wrench and J 34028 on the flats of the inner tie rod housing (7). See «Special Tools»(ref-238245-S22550396302006072400000) . Tighten: Tighten the inner tie rod to 100 N.m (74 lb ft).
11. Place the inner tie rod assembly (2) in a vise.
12. Stake both sides of the female inner tie rod assembly housing to the male rack (1).
13. Insert a 0.25 mm gage (1) between the rack (2) and the inner tie rod housing in order to check both stakes. The feeler gage (1) must not pass between the rack and the housing stake.
14. Slide the shock dampener (2) over the inner tie rod housing (3) until the front lip of the shock dampener (2) bottoms against the inner tie rod housing (3).
15. To assemble the rack and pinion boot. Refer to «Rack and Pinion Boot and Breather Tube Replacement - Off Vehicle»(ref-238245-S01618047252006072400000) .

Scheme 110

1. Remove the rack and pinion boot. Refer to «Rack and Pinion Boot and Breather Tube Replacement - Off Vehicle»(ref-238245-S01618047252006072400000) .
2. Place the gear in a vise.
3. Remove the shock dampener (4) from the inner tie rod assembly (6).
4. Slide the shock dampener (4) back on the rack (5).
5. Place a pipe wrench on the rack (5) next to the inner tie rod housing (6).
6. Place a wrench on the flats of the inner tie rod housing (6).
7. Rotate the inner tie rod housing (6) counterclockwise, while holding the rack stationary, until the inner tie rod separates from the rack (5).
8. Remove the shock dampener (3) from the inner tie rod housing (2).
9. Slide the shock dampener (3) back on the rack (5).
10. Place a pipe wrench on the rack.
11. Place a wrench on the flats of the inner tie rod housing (2).
12. Rotate the inner tie rod housing (2) counterclockwise, while holding the rack stationary, until the inner tie rod (1) separates from the rack (5).
13. If female rack (1) and male inner tie rod (3), remove the old LOCTITE® from the threads (2) of the inner tie rod and the rack. If male rack (5) and female inner tie rod (4) LOCTITE® will not be present.

Scheme 111

1. Slide the shock dampener (4) forward onto the rack (3).
2. If female rack (3) and male inner tie rod (2), apply LOCTITE® 262 or equivalent to the inner tie rod threads.
3. Attach the inner tie rod onto the rack (3).
4. Place a pipe wrench on the rack (3) next to the inner tie rod housing (2).
5. Place a torque wrench and J 34028 on the flats of the inner tie rod housing (2). See «Special Tools»(ref-238245-S22550396302006072400000) . Tighten: Tighten the inner tie rod to 100 N.m (74 lb ft).
6. Slide the shock dampener (2) forward onto the rack.
7. If female rack and male inner tie rod (1), apply LOCTITE® 262 or equivalent to the inner tie rod threads.
8. Attach the inner tie rod (1) onto the rack.
9. Place a pipe wrench on the rack next to the inner tie rod housing (4).
10. Place a torque wrench and J 34028 on the flats of the inner tie rod housing (7). See «Special Tools»(ref-238245-S22550396302006072400000) . Tighten: Tighten the inner tie rod to 100 N.m (74 lb ft).
11. Place the inner tie rod assembly (2) in a vise.
12. Stake both sides of the female inner tie rod assembly housing to the male rack.
13. Insert a 0.25 mm gage (1) between the rack (2) and the inner tie rod housing in order to check both stakes. The feeler gage (1) must not pass between the rack and the housing stake.
14. Slide the shock dampener (2) over the inner tie rod housing (3) until the front lip of the shock dampener (2) bottoms against the inner tie rod housing (3).
15. To assemble the rack and pinion boot. Refer to «Rack and Pinion Boot and Breather Tube Replacement - Off Vehicle»(ref-238245-S01618047252006072400000) .

Scheme 112

Scheme 113

1. Loosen both cylinder line fittings on the cylinder end of the gear assembly.
2. Loosen both fittings on the cylinder line assemblies (1) at the valve end of the gear assembly.
3. Remove both cylinder line assemblies (1) from the rack and pinion gear assembly (2).
4. Remove the O-ring seals (1) from the valve end of line.
5. Discard the O-ring seals (1).

J 29810 Stub Shaft Seal Protector. See Special Tools .

Scheme 114

Scheme 115

1. Remove the steering gear from the vehicle, refer to «Power Steering Gear Replacement (Rack and Pinion)»(ref-238245-S42805360982006072400000) or «Power Steering Gear Replacement (Non Rack and Pinion)»(ref-238245-S40926665712006072400000) .
2. Remove the adjuster plug lock nut (5) from the adjuster plug (4).
3. Remove the adjuster plug (4) from the gear assembly (1).
4. Remove the adjuster spring (3) and the rack bearing (2).
5. Remove the spool shaft boot (1) from the rack and pinion gear assembly.
6. Remove the retaining ring (2) from the valve bore of the rack and pinion gear assembly.
7. Remove the dust cover (4) from the bottom of the rack and pinion gear assembly.
8. Remove the hex lock nut (3) from the lower end of the pinion and valve assembly while holding the stub shaft with a 14 mm crowfoot wrench.
9. Using an arbor press (1), press on the threaded end of the pinion until removal of the following items is possible: The stub shaft (4) The stub shaft seal (2) The stub shaft bearing annulus assembly (3)

Scheme 116

Scheme 117

1. Install the hex lock nut (1) onto the pinion while holding the valve stub shaft. Tighten: Tighten the nut to 30 N.m (22 lb ft).
2. Install the dust cover (2) to the rack and pinion gear assembly.
3. Install the stub shaft bearing annulus assembly (1) onto the valve stub shaft (2).
4. Install J 29810 onto the valve stub shaft. See «Special Tools»(ref-238245-S22550396302006072400000) .
5. Lubricate the stub shaft seal (3) with grease.
6. Install the stub shaft seal (3) into the rack and pinion gear assembly.
7. Install the retaining ring (2) into the groove in the rack and pinion gear assembly.
8. Install the spool shaft boot (1) onto the rack and pinion gear assembly.
9. Lubricate the following items with lithium base grease: The rack bearing (2) The adjuster spring (3) The adjuster plug (4)
10. Install the following items into the gear assembly: The rack bearing (2) The adjuster spring (3) The adjuster plug (4)
11. Turn the adjuster plug (1) clockwise onto the rack and pinion gear assembly until the adjuster plug (1) bottoms in the rack and pinion gear assembly, then turn the adjuster plug (1) back 50 degrees to 70 degrees.
12. Check the rotational torque on the pinion. The maximum pinion preload torque is 1.8 N.m (16 lb in).
13. Install the adjuster plug lock nut (5) to the adjuster plug (4). Finger tighten the adjuster plug lock nut (5) while holding the adjuster plug (4) stationary. Tighten: Tighten the nut to 68 N.m (50 lb ft).
14. Install the steering gear into the vehicle, refer to «Power Steering Gear Replacement (Rack and Pinion)»(ref-238245-S42805360982006072400000) or «Power Steering Gear Replacement (Non Rack and Pinion)»(ref-238245-S40926665712006072400000) .
15. Refer to «Bleeding the Power Steering System»(ref-238245-S37963845102006072400000) .

EHPS Module

The elector-hydraulic power steering (EHPS) module shall interface with the vehicle electrical subsystem to provide connections for the +36-volt nominal power supply, for signal inputs necessary to control the EHPS module output and for serial communications. If the 125 A EHPS fuse or the +36-42 volt circuit supplying the EHPS module is open, the EHPS system will not operate and only communication codes will be set by modules which communicate with the EHPS module. The 125 A EHPS fuse is molded in to the 36-42 volt harness, and is located under the starter/generator control module (SCGM). If the 125 A fuse is open, refer to Positive and Negative Battery Cable (42V) Replacement (5.3L Engine w/RPO HP2) in Engine Electrical. The powertrain control module (PCM) shall act as the gateway to translate controller area network (CAN) messages into class 2 messages when required for diagnostic purposes.

The EHPS module shall receive the following messages from the CAN bus

1. Vehicle speed in km/h
2. Service disconnect status
3. Shift lever PRNDL position
4. Torque converter clutch (TCC)/Cruise Dump signal, for zero-adjust brake switch position

The EHPS module shall output the following messages to the CAN bus

1. Brake pedal rate, position, in-range rationality, and out-of-range diagnosis
2. EHPS system status
3. Diagnostic messages to driver information center (DIC) via hybrid control module (HCM)
4. Diagnostic information requested by service technicians via Tech 2 link (class 2 via PCM)
5. Steering wheel sensor diagnostic message (in-range, out-or-range failure)

The EHPS module receives several hardwire signals. Digital steering wheel speed signals from the steering wheel sensor mounted on the steering column and an analog brake pedal position signal from the brake-pedal mounted brake pedal position (BPP) sensor.

The steering wheel speed sensor outputs 3 digital signals characterizing the steering wheel position. The digital output consist of 3 open collector output data lines referred to as phase A, phase B, and Index. The normal operating range of the digital signals is plus or minus 720 degrees of steering wheel rotation. Phase A and phase B are 90 degrees out of phase to provide quadrature pulsed data corresponding to steering shaft rotational displacement and direction. The signal is resolved to within 1 mechanical degree of resolution. The index output references a steering wheel mechanical position of 0° plus or minus 10 degrees (steering wheel centered) and is repeated every 360 degrees of steering wheel rotation.

The BPP sensor outputs an analog signal, referenced to 5 volts, which may increase or decrease monotonically with brake pedal depression. The sensor analog output shall have a specified electrical output over a mechanical range of 32 degrees (rotation of the brake pedal pivot). Out-of-range values will be provided outside of the 32 degrees range. The electrical range of the BPP sensor motion is -55 degrees to +25 degrees. The mechanical range of the BPP sensor is -70 degrees to +40 degrees.

The EHPS module also receives ignition key position signals. These signals are the ignition signal and the accessory signal. The EHPS module receives an ignition input (ignition 1) on the 24-way signal connector. Ignition signal logic is defined as follows

1. When the ignition switch is in the RUN or CRANK positions, then Ignition 1 = high, greater than 6 volts for more the 50 milliseconds.
2. When the ignition switch is in the LOCK/OFF or ACCY positions, then Ignition 1 = low, less than 3 volts for more than 0.5 milliseconds.

The EHPS module receives an input from the ignition 0 circuit indicating when the key is in the ACCY position. This input has 2 functions, to provide an independent wake-up signal in the event of loss of the ignition input, and to activate the EHPS module when the key remains in the ACCY position. The ACCY signal logic is defined as follow

1. When the ignition switch is in the ACC or RUN positions, then Ignition 0 = high, greater than 6 volts for more than 50 milliseconds.
2. When the ignition switch is in the LOCK/OFF or CRANK positions, the Ignition 0 = low, less than 3 volts for more than 5 milliseconds.

The EHPS module will function normally when the voltage at the EHPS connector is in the range of 34-50 volts. If the supply voltage at the EHPS connector drops below 18 volts for more than 10 ms, the EHPS module shall go into the Standby mode (power stage turned OFF). Once the supply voltage rises above 22 volts again, the power stage shall be turned back ON without a key cycle being required. If the supply voltage drops below 12 volts, the EHPS module drivers shall shut down and a key cycle will be required to reset. The EHPS module shall withstand voltage up to a transient voltage of 58 volts for 400 milliseconds. If the supply voltage exceeds 55 volts, the EHPS module drivers shall shut down and a key cycle will be required to reset.

EHPS system performance may be reduced with power steering fluid temperature change. The temperature range at which full performance is achieved is approximately -20 to +105°C (-4 to +220°F). The EHPS system performance will be affected as follows

1. At approximately less than -40°C (-40°F), the system will be disabled.
2. At approximately -40 to -29°C (-40 to -20°F), the hydraulic output power reduction less than 50 percent.
3. At approximately -29 to -20°C (-20 to -4°F), the hydraulic output power reduction less than 20 percent.
4. At approximately -20 to +105°C (-4 to +221°F), the hydraulic output power is at full performance.
5. At approximately 105-135°C (220-275°F), the hydraulic output power reduction less than 20 percent.
6. At approximately greater than 135°C (275°F), the system will be disabled.

EHPS system performance may also be reduced with voltage change. The voltage range at which full performance is achieved is approximately 34-50 volts. The EHPS system performance will be affected as follows

1. At approximately less than 18 volts, the EHPS system will be disabled.
2. At approximately 18-33 volts, the EHPS system performance is reduced.
3. At approximately 34-50 volts, the EHPS module will be at full performance.
4. At approximately greater than 55 volts, the EHPS module will be disabled.

Whenever a replacement EHPS power pack is installed, reprogramming is necessary. If the EHPS power pack is not programmed, DTC C0564 will be set.

The hydraulic power steering pump is a constant displacement vane-type pump that provides hydraulic pressure and flow for the power steering gear. The hydraulic power steering pumps are either belt-driven or direct-drive, cam-driven.

The power steering fluid reservoir holds the power steering fluid and may be integral with the power steering pump or remotely located. The following locations are typical locations for the remote reservoir

1. Mounted to the front of the dash panel
2. Mounted to the inner fender
3. Mounted to a bracket on the engine

The 2 basic types of power steering gears are listed below

1. A recirculating ball system
2. A rack and pinion system

In the recirculating ball system, a worm gear converts steering wheel movement to movement of a sector shaft. A pitman arm attached to the bottom of the sector shaft actually moves one tie rod and an intermediate rod move the other tie rod.

In the rack and pinion system, the rack and the pinion are the 2 components that convert steering wheel rotation to lateral movement. The steering shaft is attached to the pinion in the steering gear. The pinion rotates with the steering wheel. Gear teeth on the pinion mesh with the gear teeth on the rack. The rotating pinion moves the rack from side to side. The lateral action of the rack pushes and pulls the tie rods in order to change the direction of the vehicle's front wheels.

The power steering pressure hose connects the power steering pump union fitting to the power steering gear and allows pressurized power steering fluid to flow from the pump to the gear.

The power steering return hose returns fluid from the power steering gear back to the power steering fluid reservoir. The power steering return line may contain an integral fin-type or line-type power steering fluid cooler.

In a typical power steering system, a pump generates hydraulic pressure, causing fluid to flow, via the pressure hose, to the steering gear valve assembly. The steering gear valve assembly regulates the incoming fluid to the right and left chambers in order to assist in right and left turns.

Turning the steering wheel activates the valve assembly, which applies greater fluid pressure and flow to 1 side of the steering gear piston, and lower pressure and flow to the other side of the piston. The pressure assists the movement of the gear piston. Tie rods transfer this force to the front wheels, which turn the vehicle right or left.