Suspension Control ( Automatic - Electronic ): Description and Operation

SUSPENSION CONTROL: ACTIVE HEIGHT CONTROL SUSPENSION: SYSTEM DIAGRAM

SYSTEM DESCRIPTION

1. SYSTEM DESCRIPTION

(a) Vehicle height auto-leveling function:

This function maintains a fixed vehicle height regardless of load conditions (occupants, cargo).

(b) Vehicle speed sensing function:

When the vehicle height is NORMAL and the vehicle speed is approximately 100 km/h (62 mph), the vehicle height automatically lowers to FAST LO. When the vehicle speed decreases to approximately 80 km/h (50 mph), the vehicle height automatically returns to NORMAL. When the vehicle height is HI, the vehicle height automatically returns to NORMAL at a vehicle speed of approximately 30 km/h (19 mph). When the vehicle height is LO, the vehicle height automatically returns to NORMAL at a vehicle speed of approximately 12 km/h (8 mph) or more.

When the transfer position switch is set to L4, the vehicle height automatically changes to HI at a vehicle speed of approximately 3 km/h (2 mph). When the vehicle speed reaches approximately 40 km/h (25 mph), the vehicle height automatically lowers to L4 HI. When the vehicle speed decreases to approximately 20 km/h (12 mph), the vehicle height automatically rises to HI.

(c) Extra-high vehicle height control:

When the transfer is in the L4 position and the vehicle height is HI, the vehicle height automatically rises +20 mm (+0.787 in.) from HI if the suspension control ECU determines the vehicle is stuck.

For vehicles with CRAWL (CRAWL control), when the transfer is in the L4 position, the vehicle height automatically rises +20 mm (+0.787 in.) from HI if the suspension control ECU receives information from the skid control ECU via CAN communication that CRAWL control is operating.

(d) Easy access mode control:

With the vehicle height NORMAL, vehicle height control not operating, the engine running, easy access mode on and the shift lever in P, when the engine switch is turned off, the vehicle height lowers to ACCESS LO. If the vehicle is driven with the vehicle height in ACCESS LO, when the vehicle speed reaches approximately 12 km/h (7 mph) or more, the vehicle height returns to normal.

(e) Spring rate switching control (front only):

Located in the front suspension control valve.

(1) During normal driving, the low gas, high gas, and relief gas springs are used to maintain a low wheel rate with the spring rate switching valve open.

HINT
Low Gas Spring: Front suspension control accumulator

High Gas Spring: Front No. 2 suspension control accumulator

Relief Gas Spring: Front No. 1 suspension control accumulator

(2) When the steering wheel is turned and a yaw rate is detected while the vehicle is driven at a speed of 30 km/h (19 mph) or more, or when the brake pedal is depressed while the vehicle speed is 50 km/h (31 mph) or more, the high gas and relief gas springs are used to maintain a high wheel rate with the spring rate switching valve closed.

3. FAIL-SAFE FUNCTION

(a) When the system is determined to be malfunctioning, the vehicle height is returned to NORMAL at a vehicle speed of 30 km/h (19 mph) only when possible.

(b) Conditions when vehicle height control stops:

When the stop light switch is on, after operating for a few seconds, control stops. However, when the transfer is in the L4 position, control does not stop.

When the vehicle is driving on an uneven road and the vehicle height increases or decreases rapidly due to bumps, etc., control stops.

On an inclined road, when the inclination is approximately 20° front to back or approximately 17° side to side, control stops.

When the height control pump and motor continuously operates for approximately 85 seconds, control stops.

When the oil temperature is -30°C (-22°F) or less, or 100°C (212°F) or more, control stops.