DaimlerChrysler LH New Yorker 1994, Электронное руководство по обслуживанию

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Amber ABS Warning Lamp goes on refer to the 1994
M.Y. Teves Mark IV Anti-Lock Brakes Diagnostic
Manual.
(3) If the Amber ABS Warning Lamp remains OUT,
drive the vehicle a short distance. During this test
drive be sure that the vehicle achieves at least 25
mph. Brake to at least one complete stop and again
accelerate to 25 mph.
(4) If a functional problem with the A.B.S. system
is determined while test driving a vehicle. Refer to
the 1994 M.Y. Teves Mark IV Anti-Lock Brakes Diag-
nostics Manual for required test procedures and
proper use of the DRB II scan tool.
ABS BRAKE SYSTEM ON VEHICLE SERVICE
The following are general precautions which
should be observed when servicing and diagnos-
ing the ABS system and/or other vehicle sys-
tems. Failure to observe these precautions may
result in ABS system damage.
(1) If welding work is to be performed on a vehicle
using an arc welder, the (CAB) should be discon-
nected before the welding operation begins.
(2) The (CAB) connector should never be connected
or disconnected with the ignition in the on position.
(3) Some components of the ABS system are not
serviced separately and must be serviced as complete
assemblies. Do not disassemble any component which
is designated as non-serviceable.
CAUTION: Brake fluid will damage painted surfaces.
If brake fluid is spilled on any painted surfaces,
wash off with water immediately.
WHEEL SPEED SENSOR CABLES
Proper installation of the Wheel Speed Sensor
Cables is critical to continued system operation. Be
sure that cables are installed, routed and clipped
properly. Failure to install speed sensor cables as
shown in the on car service section of this manual.
May result in contact with moving parts or over ex-
tension of cables, resulting in component failure and
an open circuit.
MECHANICAL DIAGNOSTICS AND SERVICE
PROCEDURES
SPECIAL SERVICE TOOL
Some diagnostic procedures in this section require
the use of the DRB II scan tool. Refer to the DRB II
scan tool operators manual for its proper operational
information.
INTERMITTENT FAULTS
As with virtually any electronic system, intermit-
tent faults in the ABS system may be difficult to
accurately diagnose.
Most intermittent faults are caused by faulty elec-
trical connections or wiring. When an intermittent
fault is encountered, check suspect circuits for:
(1) Poor mating of connector halves or terminals
not fully seated in the connector body.
(2) Improperly formed or damaged terminals. All
connector terminals in a suspect circuit should be
carefully reformed to increase contact tension.
(3) Poor terminal to wire connection. This requires
removing the terminal from the connector body to
inspect.
(4) Pin presence in the connector assembly
If a visual check does not find the cause of the
problem, operate the car in an attempt to duplicate
the condition and record the Fault code.
Most failures of the ABS system will disable Anti-
Lock function for the entire ignition cycle even if the
fault clears before key-off. There are some failure
conditions, however, which will allow ABS operation
to resume during the ignition cycle in which a failure
occurred. If the failure conditions are no longer
present. The following conditions may result in inter-
mittent illumination of the Amber Anti-Lock Warning
Lamp. All other failures will cause the lamp to re-
main on until the ignition switch is turned off. Cir-
cuits involving these inputs to the (CAB) should be
investigated if a complaint of intermittent warning
system operation is encountered.
(1) Low system voltage. If Low System Voltage (9
volts or less) is detected by the (CAB), the (CAB) will
turn on the Amber Anti-Lock Warning Lamp until
normal system voltage is achieved. Once normal volt-
age is seen at the (CAB), normal operation resumes.
(2) Main Relay. If the relay fails to make the
ground circuit connection or is an intermittent
ground. The (CAB) will turn on the Amber Anti-Lock
Warning Light.
Additionally, any condition which results in inter-
ruption of power to the (CAB) or (HCU) assembly
may cause the Amber Anti-Lock Warning Lamp to
turn on intermittently.
ABS BRAKE SYSTEM DIAGNOSTIC FEATURES
SYSTEM INITIALIZATION
System initialization starts when the ignition
switch is turned to the run position. At this point the
(CAB) performs a complete self check of all electrical
components in the Anti-Lock and Traction Control
systems. Momentarily the build, decay and isolation
valves are cycled. If the driver has his foot on the
brake pedal, they may feel the test through brake
pedal pulsations. This is a normal condition.
DYNAMIC TEST
Between 5 - 10 mph the pump/motor is momen-
tarily turned on.
5 - 90 ANTI-LOCK BRAKE SYSTEM