Introduction; System Coverage; Six-Step Troubleshooting Procedure; Identification Of System - Jeep KJ Liberty Cherokee 2003 Service Manual

1.0 INTRODUCTION

The procedures contained in this manual include
all the specifications, instructions, and graphics
needed to diagnose the 2003 Jeep Liberty Mark 20e
Antilock Braking System (ABS) problems. The di-
agnostics in this manual are based on the failure
condition or symptom being present at time of
diagnosis.
Follow the recommendations below when choos-
ing your diagnostic path.
1. First make sure the DRBIII is communicating
with the CAB. If the DRBIII
Response'' condition, you must diagnose that
first.
2. Read DTC's (diagnostic trouble codes) with the
DRBIII .
3. If no DTC's are present, identify the customer
complaint.
4. Once the DTC or customer complaint is identi-
fied, locate the matching test in the Table of
Contents and begin to diagnose the symptom.
All component location views are in Section 8.0.
All connector pinouts are in Section 9.0. All sche-
matics are in Section 10.0.
An * placed before the symptom description indi-
cates a symptom with no associated DTC.
When repairs are required, refer to the appropri-
ate service manual for the proper removal and
repair procedure.
Diagnostic procedures change every year. New
diagnostic systems may be added; carryover sys-
tems may be enhanced. READ THIS MANUAL
BEFORE TRYING TO DIAGNOSE A VEHICLE
CODE. It is recommended that you review the
entire manual to become familiar with all new and
changed diagnostic procedures.
After using this book, if you have any comments
or recommendations, please fill out the form at the
back of the book and mail it back to us.

1.1 SYSTEM COVERAGE

This diagnostic manual covers the Teves Mark
20e Antilock Braking System (ABS) found on the
Jeep Liberty.
1.2 SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the antilock brake system is done in
six basic steps:
•
verification of symptom
•
verification of any related symptoms
• symptom analysis
• problem isolation
•
repair of isolated problem
• verification of proper operation
2.0 IDENTIFICATION OF
Vehicles equipped with the Teves Mark 20e an-
tilock brake system can be identified by the pres-
ence of the combined Controller Antilock Brake
(CAB) and Hydraulic Control Unit (HCU)/Pump Mo-
tor assembly mounted by the master cylinder.
displays a ''No
3.0 SYSTEM DESCRIPTION AND
3.1 TEVES MARK 20e SYSTEM
A Controller Antilock Brake (CAB) is used to
monitor wheel speeds and to modulate (control)
hydraulic pressure in each brake channel to pre-
vent wheel lock-up during braking. The CAB also
provides a vehicle speed signal (VSS) to the Body
Control Module (BCM).
During a non-ABS stop, the system functions as a
standard front/rear split configuration. The pri-
mary supplies brake fluid pressure to the front
brakes, and the secondary supplies the rear brakes.
A conventional combination/proportioning valve is
not used. This system uses the existing ABS sole-
noids to replace and perform the same functions
that the combination and proportioning valves do.
The CAB has a special software program called
Electronic Variable Brake Proportioning (EVBP),
that monitors the wheel speeds so that when cer-
tain criteria are met the software will enable the
solenoids to perform the same brake fluid manage-
ment control as the combination/proportioning valves.
During an ABS stop, the system still uses the
front/rear hydraulic split; however, the brake sys-
tem pressure is further split into three control
channels. During ABS operation, the front wheels
are controlled independently and are on two sepa-
rate control channels. The rear wheels are con-
trolled together through one control channel. By
using separate control channels for each front
wheel, more steering control is maintained during
maximum braking.
During an antilock stop, ''wheel lock-up'' does not
necessarily mean that the wheel has locked, it
means only that the wheel is turning slower than
the vehicle speed. This is called ''wheel slip'' and is
indicated as a percentage. 0% slip means that the
wheel is rolling free and 100% slip means that the
1
GENERAL INFORMATION
SYSTEM
FUNCTIONAL OPERATION
DESCRIPTION