Pontiac Fiero 1988 Service Manual page 1038

E L E C T R I C S T E E R I N G A S S I S T
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• For diagnosis, see Section 3.
T R O U B L E S H O O T I N G HINTS
• Try the following checks before doing the Sys-
tem Check.
1. Check the FAN E Fuse by observing
Coolant Fan operation.
2. Verify that fluid level is correct and that
proper fluid (Electro-Hydraulic Steering
Fluid #9985567) is being used-refer to Sec-
tion 3B3 of the Service Manual.
3. Check that ground G502 is clean and tight.
4. Verify that all EHPS Controller connections
are clean and secure.
C I R C U I T OPERATION
The Electro-Hydraulic Power Steering
(EHPS) System employs an electrically driven
hydraulic pump to provide hydraulic power
assisted steering. This eliminates the need for a
belt driven hydraulic pump. The amount of
power steering assistance is varied in propor-
tion to the car's speed. At a complete stop, the
available assistance is maximum. Since the
pump is electrically driven, the maximum
assistance is available even when the engine is
stopped (Ignition still in RUN). The assistance
will decrease as the vehicle speed increases; this
increases road "feel" at higher speeds. At
approximatley 50 mph the assistance will be
minimal and the steering will be similar to man-
ual steering.
C O M P O N E N T LOCATION
Page-Figure
Electro-Hydraulic Power Steering
(EHPS) Controller Lower LH side of front compartment 201- 3-D
Electro-Hydraulic Power Steering
(EHPS) Pump Motor Lower LH side of front compartment . . 201- 3-D
Fuse Block . . Behind LH side of I/P 201- 6-D
Fusible Link X RH front of engine compartment, at Battery
Junction Block 201- 4-A
C100 (34 cavities) LH side of front bulkhead, right of brake master
cylinder. 201-13-A
G101 On LH fender, below headlamp 201-11-C
G102 On RH fender, below headlamp 201-11-C
G502 Engine compartment, on battery tray 201- 2-C
S100 Forward lamp harness, behind LH headlights . . . 201-11-C
S103 Forward lamp harness, near bulkhead connector. 201-10-C
S215 Main harness, behind I/P, near front of console . . 201-15-A
The EHPS Controller has two voltage inputs.
When the Ignition Switch is turned to RUN,
voltage is applied to connector CI terminal B.
When the controller receives this voltage, it will
ground the relay thereby closing the relay con-
tacts. Voltage is then applied from Fusible Link
X, through the relay contacts, to the Pump
Motor, and back through the EHPS Controller
to ground. The Pump Motor can then provide
maximum steering assistance.
The vehicle speed input is at connector CI,
terminal D. The EHPS Controller will vary the
amount of voltage applied to the motor in rela-
tion to the vehicle speed. The higher the vehicle
speed, the less voltage that the EHPS Control-
ler will apply to the Pump Motor. This reduces
the power of the Pump Motor, causing less
power steering assistance.