1991 ACURA NSX service

Component Location
Index

NOTE:
If an intact airbag assembly has been removed from a scrapped car or has been found defective or damaged during
transit, storage or service, it should be deployed (see section 23). Before removing the gearbox, remove the ignition key to lock the steering shaft from turning.
After installing the gearbox, check the wheel alignment and adjust if necessary.
STEERING WHEEL/AIRBAG ASSEMBLY

Removal, page 17-8

Disassembly, page 17-9

Installation, page 17-10

STEERING COLUMN
Removal, page 17-12
Inspection, page 17-14 Installation, page 17-15
STEERING GEARBOX
Removal/Installation, page 17-19 Disassembly, page 17-22

Inspection, page 17-21

Reassembly, page 17-25ProCarManuals.com

Self-Diagnosis Function

The EPS control unit monitors the system inputs and outputs, and the driving current of the motor. If there is a problem

in the system, the control unit turns the system off by actuating the relay in the power unit. Power assist stops and

normal manual steering operation resumes. The control unit also turns the EPS indicator light on to alert the driver, and

memorizes the problem in the form of a code. Connecting the terminals of the service check connector with a jumper

wire enables the EPS indicator light to blink the problem code when the ignition switch is turned on.

Unloader Control

If the steering wheel is turned fully and held in the full-lock position, the steering torque reaches the maximum point,

and an over-current flows to the motor and the power unit. The control unit detects this and reduces the current flow

to the motor.

Average Moving Current Control

The electric current flow to the motor is estimated from the current values detected by the current sensor, and the aver-

age current is obtained at two second intervals. The motor driving current is suppressed when the average current value

exceeds a predetermined marginal value. The control unit regurates the motor current during continuous loading to sup-

press any excessive temperature rise in the power unit and the motor.

Over-Voltage Control

If there is an excessive increase in power source voltage due to a poor battery condition, an alternator voltage regulator

problem, etc., the motor assisting force increases, resulting in excessive control. To prevent this, the control unit signals

to the power unit are corrected to ensure that adequate assisting force is generated.ProCarManuals.com

Troubleshooting Procedures

Under normal conditions, the EPS indicator light in the gauge assembly comes on when the ignition switch is turned

to the ON position, then goes off after the engine is started. This indicates that the bulb and its circuits are operating

correctly.

EPS INDICATOR LIGHT

When the EPS control unit senses an abnormality in the system, the control unit memorizes the problem, the EPS indica-

tor light blinks at equal intervals, and the power steering assist is turned off.

When the EPS indicator light has been reported on, connect the two terminals of the service check connector with a

jumper wire. Then turn on the ignition switch and observe the blinking frequency.

SERVICE CHECK

CONNECTOR (BLU)

GRN/WHT

SERVICE CHECK CONNECTOR (BLU)
BLUProCarManuals.com

Troubleshooting

Diagnostic Trouble Code (DTC) Display

When the service check connector terminals are connected with a jumper wire, the EPS control unit blinks the EPS indi-
cator light to indicate the DTC. The DTC is indicated by a series of long and short blinks. One long blink equals 10 shortblinks. Add the long and short blinks together to determine the DTC, then refer to the Troubleshooting Chart on page 17-51.

Example 1.3 seconds
0.28 seconds
1.3 seconds

0.36 seconds
The control unit can memorize any number of simultaneous problems. The DTC is repeated sequentially beginning with
the lowest number.
The DTC is stored in the control unit memory even when the ignition switch is turned off. After repairing the EPS system,
disconnect the CLOCK fuse in the relay box for more than 10 seconds to reset the EPS control unit memory.ProCarManuals.com

Troubleshooting Chart
The EPS has been reported on: Connect the service check connector with a jumper wire (see page 17-43). Turn on the ignition switch.Read the Diagnostic Trouble Code (DTC) and perform the troubleshooting according to the troubleshooting chart below.

17-52

17-54

17-56

17-59

17-60

17-62ProCarManuals.com

Component Location

Index

NOTE:

EPS CONTROL UNITReplacement, page 17-74
POWER UNIT
Replacement, page 17-73
STEERING WHEEL/
AIRBAG ASSEMBLYRemoval, page 17-8
Disassembly, page 17-9

Installation, page 17-10

STEERING COLUMN
Removal, page 17-12

Inspection, page 17-14

Installation, page 17-15

STEERING GEARBOX Removal/Installation, page 17-64

Illustrated Index, page 17-68

Pinion Preload Inspection, page 17-69

Rack Guide Screw Adjustment, page 17-69
If an intact airbag assembly has been removed from a scrapped car or has been found defective or damaged during
transit, storage or service, it should be deployed (see section 23).
Before removing the gearbox, remove the ignition key to lock the steering shaft.
After installing the gearbox, check the wheel alignment and adjust if necessary.ProCarManuals.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

Troubleshooting
TCS Indicator Light

Temporary Driving Conditions:
1. The TCS indicator light will come on and the control unit memorizes the Diagnostic Trouble Code (DTC) under cer-
tain temporary conditions:
2. If the TCS indicator light does not come back on after correcting the tire or tire pressure problem, the TCS system is
OK.

NOTE: Remove the ABS 2.3 (20 A) fuse for at least 3 seconds to clear the DTC from the TCS control unit memory.
TCS Diagnostic Trouble Code (DTC) Indication: 1. Stop the engine.
2. Turn the ignition switch on and confirm that the TCS indicator light comes on.
3. Turn the ignition switch off.
4. Connect the two terminals of the Service Check Connector with a jumper wire.
5. Turn the ignition switch on, but do not start the engine.6. Record the blinking frequency of the TCS indicator light. The blinking frequency indicates the DTC. Long blinks in- dicate the main code: short blinks indicate the sub-code.
7. Refer to the Troubleshooting Guide (page 19-84) for repair information. The spare tire is installed, or a tire of the improper size is installed.
The tire pressures are not correct.
SERVICE CHECK CONNECTOR (BLU)
SERVICE CHECK

CONNECTOR (BLU)
INDICATOR LIGHTProCarManuals.com