1991 ACURA NSX traction control

System Description

Suspension Composition

Outline

Double wishbone independent suspension has been selected for each of the four wheels. This eliminates damper friction

along the steering axis, and permits suspension geometry that takes full advantage of the performance potential of the

wide, low aspect ratio tires. The double wishbone design also allows the use of aerodynamically-efficient and

aesthetically pleasing low fender lines.

The knuckles and the suspension arms are manufactured from lightweight, high-strength aluminum alloys. This gives a

notable reduction in unsprung weight which results in increased traction and improved ride. It also allows the individual

suspension components to be designed in detail for maximum strength and rigidity.

FRONT

UPPER

CONTROL

ARM
KNUCKLE

STABILIZER
REAR

UPPER

CONTROL

ARM
STABILIZER

KNUCKLE

LOWER CONTROL ARM

LOWER CONTROL ARM

To further increase suspension link rigidity, and to obtain optimum knuckle geometry, the knuckles and ball joints are

contained within the wheel profile. At each corner of the car, the individual suspension system is attached to the alumi-

num stressed skin chassis by a cast aluminum sub-frame. This design further reduces overall weight, and ensures that

suspension loads are fed into the chassis at the most efficient points, and in the most efficient directions.

A large front caster angle combined with small trail distance improves straight-line stability and response without caus-

ing heavy steering effort.

FRONT
REAR

SUB-FRAME

SUB-FRAMEProCarManuals.com

System Description

TCS Control unit

Acceleration Control:

The TCS control unit gets signals from the wheel sensors about the rotational speed of each wheel. Traction control

is activated when the rotational speed of the driving wheels differs from the rotational speed of the driven wheels (i.e.,

vehicle speed).

Handling Control:

Based on signals about driving wheel and driven wheel rotational speeds, the control unit calculates the car's "yaw"

rate (i.e., the turn rate of the car's body). Based on signals from the steering angle sensor, the control unit also calculates

the yaw rate expected by the driver. If the difference between actual and expected yaw rates is substantial—that is,

if the direction of the car's body will exceed the driver's expected line—the control unit signals the throttle actuator,

which closes the throttle valve, thus reducing engine power and maintaining the expected line.

Rough Road Control:

Based on signals from the wheel sensors, the control unit detects a rough road based on frequency of wheel rotational

vibration. The control unit then signals the throttle actuator to relax engine power, thus improving acceleration efficiency.

Grip Control:

Based on signals about wheel speed and yaw rate, the control unit determines the efficiency of the grip of the tires on

the road and signals the throttle actuator to relax engine power if necessary, thus improving grip.
Construction and Function

DRIVE WHEELS

Right wheel

Left wheel
WHEEL SENSORS

Driving Wheel

Speed
Average speed

of left and

right wheels

Vehicle speed

Advance acceleration

Tire grip control

Acceleration

control

Target slip

ratio

Engine control block

ENGINE CONTROL

MODULE (ECM)
Throttle actuator (step motor)
Throttle valve control
Handling control
Rough road

detection

Rough road

control
Reference yaw rate

Lateral

acceleration
TCS CONTROL UNIT
STEERING ANGLE SENSOR

DRIVEN WHEELS

Right wheel
Left wheel

Actual

yaw rate
Rotational

vibration
Speed difference in the

left and right wheelsProCarManuals.com

Fail-Safe Function:

If the control unit detects an abnormality, it shuts the

traction control system off and causes the TCS in-

dicator light to come on. However if the abnormality is

detected while the TCS is activated, the control unit

first establishes the appropriate wheel spin velocity,

then shuts the system down, thus preventing excessive

wheel spin.

Self-Diagnosis Function:

If the control unit detects an abnormality, it records a

Diagnostic Trouble Code (DTC) which can be used to

diagnose the problem. The DTC is shown at the TCS in-

dicator light when the Service Check connector ter-

minals are connected with a jumper wire.

Steering Angle Detection

Steering angle is detected by the steering angle sensor,

located on the steering column. The sensor uses two

magneto-resistor (MR) elements to determine steering

angle and direction of rotation. When the driver turns

the steering wheel, a magnet in the steering shaft

generates waves in the "MR" elements. These waves

are amplified and converted into signals which the con-

trol unit can interpret as angle and direction of turn.

Vehicle Speed Detection

Wheel rotation speed is detected by the wheel sensors,

located at each wheel. The signals are sent to the con-

trol unit, which compares each wheel's speed and de-

termines whether traction control is required.
MR ELEMENT

WHEEL SENSOR
GEAR PULSER
MR

ELEMENT
INDICATOR LIGHTProCarManuals.com

System Description

Engine Output Control

When the TCS is activated, the control unit signals the throttle actuator, located next to the throttle valve. The throttle

actuator is linked to the throttle valve through a series of reduction gears. Although the accelerator pedal position is

still within the driver's control, the throttle valve is automatically relaxed to achieve optimum traction.
Construction and Function

LOST MOTION SPRING

(INSIDE RETURN SPRING)

THROTTLE VALVE

RETURN SPRINGS

DURING NORMAL DRIVING:

LOST

MOTION

SPRING

THROTTLE

LEVER

THROTTLE

RETURN SPRING
THROTTLE DRUM

THROTTLE

VALVE

THROTTLE ACTUATOR

(STEP MOTOR)
Movement of parts

while accelalator pedal open.

Movement of parts while

TCS is actuated.
DURING TCS ACTUATION:
THROTTLE ACTUATOR

(STEP MOTOR)
THROTTLE POSITION SENSOR
THROTTLE VALVE
THROTTLE DRUM

ACCELERATOR PEDAL

ANGLE SENSOR

TCS THROTTLE

LEVERProCarManuals.com

Troubleshooting

Anti-lock Brake System Indicator Light

Temporary Driving Conditions:
1. The anti-lock brake system indicator light will come
on and the control unit memorizes the problem
under certain conditions.
NOTE: Problem codes are explained on pages
19 - 46.
The tire(s) adhesion is lost due to excessive cor-
nering speed.
Problem codes: 5, 5-4, 5-8. The vehicle loses traction when starting from a
stuck condition on a muddy, snowy, or sandy

road.
Problem code: 4-1, 4-2, 4-4, 4-8. When the parking brake is applied for more than
30 seconds while the vehicle is being driven.
Problem code: 2. The vehicle is driven on extremely rough road.
The anti-lock brake system is OK, if the anti-lock brake system indicator light goes off after the
engine is restarted.
ANTI-LOCK BRAKE SYSTEM INDICATOR LIGHT
2. If you receive a customer's report that the anti-lock brake system indicator light sometimes comes on,
check the system using the ALB checker to confirm
whether there is any trouble in the system.

See page 19 - 41.

3. The anti-lock brake system indicator light will come on and the control unit will store a problem codewhen there is insufficient battery voltage to the
control unit. An example would be when the bat-
tery is so weak that the car must be jump-started. After the battery is sufficiently recharged, the anti-lock brake system indicator light will work normally
after the engine is stopped and restarted.
However, after recharging the battery, the problem
code must be cleared from the control unit's
memory by disconnecting the ALB 2,3 (No. 32)
fuse for at least 3 seconds. Anti-lock Brake System Indicator Light Circuit:
CAUTION: Use only the digital multimeter to

check the system.

1. The indicator light does not go on when the ignition switch is turned on.
Check the following items. If they are OK, check
the control unit connectors. If not loose or disconnected, install a new control
unit and recheck:
Blown anti-lock brake system indicator light
bulb.
Open circuit in YEL wire between No. 5 (10 A)
fuse and gauge assembly. Open circuit in BLU/WHT wire between gauge
assembly and control unit. Loose component grounding of the control unit
to the body.
2. The anti-lock brake system indicator light remains ON after the engine is started, however the anti-lock brake system indicator light does not blink any
code or sub-code. Check the following items:
Loose or poor connection of the wire harness at

the control unit.

Faulty ALB 2,3 (No. 32) fuse.
Open circuit in WHT/BLK wire between ALB 2,3(No. 32) fuse and control unit.
Open circuit in YEL/BLK wire between fuse No.

4 (1 5 A) and control unit.

Short circuit in BLU/WHT wire between gauge
assembly and control unit. Open circuit in WHT/BLU wire between alter-

nator and control unit.

If the problem is not found substitute a known-good
control unit and recheck whether the warning light re-
mains ON.ProCarManuals.com