ACURA NSX 1997 Service Repair Manual

Relay Inspection
Electronic Components

1. Check for continuity between terminals

There should be no continuity.

2. Connect a 12 V battery across terminals

There should be continuity between terminals

and
Inspection
Pulsers/Sensors

1. Check the pulser for chipped or damaged teeth.

2. Measure air gap between the sensor and pulser all

the way around while rotating the driveshaft by

hand.

(A) - (B) = Standard: 0.4 - 1.0 mm

(0.02
-
0.04
in)

NOTE: If the gap exceeds 1.0 mm (0.04 in), the

probability is a distorted knuckle which should be

replaced.ProCarManuals.com

NOTE:
• B e carefu l whe n installin g th e sensor s t o avoi d twist -
ing th e wires .
• Afte r senso r replacemen t confir m prope r operatio n
(se e pag e 19-62 ).
Fron t Senso r Replacemen t
Rea r Senso r Replacemen t
NOTE:
• B e carefu l whe n installin g th e sensor s t o avoi d
twistin g th e wires .
• Afte r senso r replacement , confir m prope r opera -
tio n (se e pag e 19-62 ).
ProCarManuals.com

19-100
Specia l Tool s
ProCarManuals.com

Component LocationsProCarManuals.com

Outline
System Description

Role of System

The NSX/NSX-T traction control is a variable system designed to enhance traction during acceleration and cornering. It

does so by determining the optimum amount of wheel spin for any given driving situation, then suppressing surplus

engine power accordingly.

This version of TCS has a lateral acceleration (Lg) sensor and a deceleration control function to improve traction control

during acceleration and deceleration while cornering. When downshifting quickly to a very low gear on a slippery surface,

the driving wheels tend to slip because of engine braking, resulting in lower directional stability. To counteract this, the

deceleration control function controls engine braking with the TCS control unit.

Construction and Function

The TCS control unit gets signals about the vehicle's speed, direction, and road conditions from sensors at the wheels and

the steering column. Based on these signals, the control unit will determine the optimum amount of wheel spin. Because

the system is variable, the control unit may determine, depending on the driving conditions, that some wheel spin is bene-

ficial (thus enhancing straight-line acceleration), or that no wheel spin is beneficial (thus enhancing cornering). For any

given driving situation, the control unit will determine the amount of wheel spin best suited to the driver's needs and, if

necessary, will then signal the throttle actuator and Engine Control Module (ECM) to reduce engine power.

The system is automatically "ready" whenever the engine is started, but can be manually canceled with the TCS switch.

However, once activated, the system cannot be canceled until it is once again in the ready state.

Components:

• Wheel sensors: The TCS "shares" the wheel sensors with the ABS. The wheel sensors transmit wheel speed signals to

the TCS through the ABS control unit.

• Steering angle sensor: The steering angle sensor signals the TCS control unit about the amount of steering angle.

• Lateral acceleration (Lg) sensor: The Lg sensor detects the lateral acceleration of the vehicle and signals the TCS con-

trol unit.

• TCS control unit: The TCS control unit detects the driving condition signals from the sensors and, if necessary, signals

the throttle actuator and the Engine Control Module (ECM). This version has a lateral acceleration (Lg) sensor, which

improves the traction control performance during cornering.

• Throttle actuator: The throttle actuator opens and closes the throttle valve according to the traction control signal from

the Engine Control Module (ECM).ProCarManuals.com

Construction and Function

TCS Control unit

Acceleration Control

When the drive wheel speed exceeds the vehicle speed by a given amount, the TCS control unit judges that the drive

wheels are slipping, and it outputs the traction control signal to reduce engine power.

Deceleration Control

When the drive wheel speed drops below the vehicle speed by a given amount, the TCS control unit judges that the drive

wheels are slipping, and it outputs the traction control signal to control engine braking properly.

Handling Control

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

(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 lateral acceleration, 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.ProCarManuals.com

Construction and Function (cont'd)
System Description

Fail-Safe Function

If the control unit detects an abnormality, it shuts the

traction control system off and causes the TCS indicator

light to come on. However if the abnormality is detected

while the TCS is activated, the control unit first estab-

lishes 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

indicator light when the Service Check connector termi-

nals are connected with the SCS service connector.

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 gener-

ates waves in the "MR" elements. These waves are

amplified and converted into signals which the control

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 deter-

mines whether traction control is required.ProCarManuals.com

Lateral Acceleration Detection

Lateral acceleration is detected by the lateral accelera-

tion (Lg) sensor located under the rear center trim panel.

The Lg sensor varies the output voltage in accordance

with the left or right side acceleration and sends it to the

TCS control unit as a lateral acceleration signal.ProCarManuals.com

TCS Control Unit Terminal ArrangementProCarManuals.com

20P CONNECTORProCarManuals.com