Steering System - Electronic Power Toyota 4Runner II

DESCRIPTION

The electronically controlled power steering system consists of a speed sensor (driven off speedometer), computer, a solenoid valve and other conventional power steering components.

The computer-controlled solenoid valve reduces hydraulic pressure to the rack at high speeds to increase steering effort. With vehicle at low speeds or stationary, the solenoid valve increases hydraulic pressure to the rack to reduce steering effort. (Scheme 1)

Scheme 1

TROUBLE SHOOTING

A malfunction in the electronically controlled power steering system will usually cause sensitive steering during high-speed driving and hard steering during idle or low-speed driving. However, these problems do not necessarily indicate a malfunction in electronically controlled power steering system. Always check following before testing electronically controlled power steering system.

1. Tire Pressure
2. Suspension & Steering Linkage Lubrication
3. Front Wheel Alignment
4. Steering System & Suspension Ball Joints
5. Bent Steering Column
6. Power Steering System Leakage
7. Power Steering Pump Pressure

DIAGNOSTIC FLOW CHARTS

Note. Use appropriate flow chart to test and diagnose system function. (Scheme 2)

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

TESTING

Note. For wiring diagrams (Scheme 6)

Solenoid Valve

1. Disconnect wiring connector from solenoid valve. Using an ohmmeter, measure resistance between solenoid valve terminals. Resistance should be 6.0-11.0 ohms. (Scheme 8) If resistance is not 6.0-11.0 ohms, replace solenoid valve.
2. Remove solenoid valve from steering gear housing. Using jumper wires, connect battery voltage to solenoid valve terminals. (Scheme 8) Ensure needle valve withdraws about.080" (2.0 mm). If needle valve does not function as described, replace solenoid valve.

Scheme 8

Speed Sensor

Remove combination meter from instrument panel. Connect ohmmeter between 2 terminals (speed sensor) near speedometer cable connector. Rotate speedometer connector. Ohmmeter should indicate continuity 4 times per rotation of speedometer.

Computer

Raise vehicle, and support it on chassis stands. Remove glove box or console. DO NOT disconnect computer connector. Start engine. Using a voltmeter, check voltage between computer terminals SOL (+) and SOL (-) with engine idling. (Scheme 9) On Cressida and Pickup and 4Runner, ensure voltage is 0-.05 volt. On Supra, voltage should be.32-.44 volt. Place transmission in gear and check computer voltage as indicated in COMPUTER VOLTAGE SPECIFICATIONS TABLE. If voltage is not to specification, replace computer.

COMPUTER VOLTAGE SPECIFICATIONS

Scheme 9

ADJUSTMENTS

There are no adjustments for this system.

REMOVAL & INSTALLATION

For complete removal and installation procedures, see appropriate STEERING SYSTEM - POWER article in the STEERING Section.

Electronic Power Steering Wiring Diagram (Cressida). Scheme 10

Electronic Power Steering Wiring Diagram (Pckup and 4Runner). Scheme 11

Electronic Power Steering Wiring Diagram (Supra). Scheme 12