Jeep 1996 Grand Cherokee Service Manual - page 187
The switch (Fig. 8), provides an additional vehicle
deceleration reference during 4-wheel drive opera-
tion. The switch is monitored by the CAB at all
times. The switch reference signal is utilized by the
CAB when all wheels are decelerating at the same
speed.
ABS SYSTEM RELAYS
The ABS system has two relays, which are the
main and motor pump relays. The main relay is used
for the solenoid valves and CAB. The main relay is
connected to the CAB at the power control relay ter-
minal. The motor pump relay is used for the motor
pump only. The pump motor relay starts/stops the
pump motor when signaled by the CAB.
ABS WARNING LAMP
The amber ABS warning lamp is located in the
instrument cluster. The lamp illuminates at start-up
to perform a self check. The lamp goes out when the
self check program determines the system is operat-
ing normal. If an ABS component exhibits a fault the
CAB will illuminate the lamp and register a trouble
code in the microprocessor. The lamp is controlled by
the CAB and or the main relay through an in-har-
ness diode. The CAB controls the lamp by directly
grounding the circuit. The main relay grounds the
lamp circuit when it is de-energized.
DIAGNOSIS AND TESTING
ABS BRAKE SYSTEM
ABS WARNING LAMP DISPLAY
The amber antilock lamp illuminates at startup as
part of the system self check feature. The lamp illu-
minates for 1-3 seconds then goes off as part of the
normal bulb check routine.
An ABS circuit fault is indicated when the amber
lamp remains on after startup, or illuminates at any
time during vehicle operation.
Verify that a fault is actually related to the ABS
system before making repairs. For example, if the
red lamp illuminates but the amber ABS lamp does
not, the problem is related to a service brake compo-
nent and not the ABS system. Or, if neither lamp
illuminates but a brake problem is noted, again, the
problem is with a service brake component and not
with the ABS system.
DRB SCAN TOOL
ABS diagnosis is performed with the DRB scan
tool. Diagnosis information is provided in the Chassis
Diagnostic Manual.
ABS DIAGNOSTIC CONNECTOR
The ABS diagnostic connector is located inside the
vehicle. The connector is the access point for the
DRB scan tool.
The connector is blue or black in color and is a
6-way type. The connector is under the carpet at the
forward end of the console just under the IP center.
SERVICE PROCEDURES
BLEEDING ABS BRAKE SYSTEM
ABS system bleeding requires conventional bleed-
ing methods plus use of the DRB scan tool. The pro-
cedure involves performing a base brake bleeding,
followed by use of the scan tool to cycle and bleed the
HCU pump and solenoids. A second base brake bleed-
ing procedure is then required to remove any air
remaining in the system.
(1) Perform base brake bleeding. Refer to base
brake section for procedure.
(2) Connect scan tool to ABS diagnostic connector
under carpet at front of console, just under instru-
ment panel center bezel.
(3) Select CHASSIS SYSTEM, followed by TEVES
ABS BRAKES, then BLEED BRAKES. When scan
tool displays TEST COMPLETE, disconnect scan tool
and proceed.
(4) Perform base brake bleeding a second time.
Refer to base brake section for procedure.
(5) Top off master cylinder fluid level and verify
proper brake operation before moving vehicle.
REMOVAL AND INSTALLATION
CONTROLLER ANTILOCK BRAKES
REMOVAL
(1) Remove harness connectors from controller.
Fig. 8 Acceleration Switch
5 - 38
BRAKES
ZJ
DESCRIPTION AND OPERATION (Continued)