Dodge RAM TRUCK 1500 1995 Service Manual page 201

B R
REAR WHEEL ANTILOCK BRAKE (RWAL) SYSTEM 5 - 29
contact with the drams. The valve is designed to
maintain front brake fluid pressure at 21-207 kPa
(3-30 psi) until the hold-off limit of approximately
807 kPa (117 psi) is reached. At this point, the me­
tering valve opens completely permitting full fluid
apply pressure to the front disc brake calipers.
REAR WHEEL ANTILOCK SYSTEM DIAGNOSIS
An antilock system malfunction will be indicated
by illumination of the amber warning lamp.
If a problem occurs, system diagnosis should begin
with a fluid level check followed by a visual exami­
nation of the system electrical and hydraulic connec­
tions. If obvious defects (low fluid, leaks, loose
connections, etc.) are not evident, road test the vehi­
cle. A road test should help determine if a malfunc­
tion is actually related to an antilock component.
During the road test, note if other conditions are
evident such as a low pedal, pull, grab, or similar
condition. Remember that brake malfunctions such
as low fluid, system leaks, or parking brakes par­
tially applied will affect antilock system operation.
The idea is to determine if a malfunction is actually
related to an antilock component.
If a visual inspection and road test do not indicate
the problem cause, check the system fault codes. Re­
fer to the system fault code information in this sec­
tion.
DIAGNOSTIC FAULT FLASH CODES
The microprocessor in the electronic control module
has a self test feature. This feature is activated
whenever the ignition switch is in the On and Run
positions.
If a system fault is detected, the control module il­
luminates the antilock light and stores the fault code
in the microprocessor memory. If a fault code is gen­
erated, the module will retain the code after turning
the ignition switch to Off position.
System faults are identified by a series of flash
codes that operate through the antilock warning
light. Temporarily grounding the antilock diagnostic
connector will produce the flash code sequence. Refer
to Fault Code Identification in this section.
FAULT CODE CAPACITY
The microprocessor memory will store and display
only one fault code at a time. The stored code can be
displayed by grounding the antilock diagnostic con­
nector.
RWAL DIAGNOSTIC CONNECTOR
Connector Location
The RWAL diagnostic connector is at the left side
of the steering column near the parking brake re­
lease handle.
The black, 2-way diagnostic connector has only one
wire attached to it. This is the 20 gauge black with
white tracer wire from test terminal 12 on the con­
trol module.
The RWAL diagnostic connector is plugged into the
data link wire connector.
How To Generate Flash Codes
Flash codes are generated by momentarily ground­
ing the diagnostic connector black wire and counting
the warning light flashes.
(a) Unplug the data link wire connector from the
RWAL diagnostic connector.
(b) Momentarily ground the RWAL diagnostic
connector black wire with a jumper wire (maintain
ground for about 2 seconds).
(c) Immediately note and record the number of
flashes at the antilock warning light.
FAULT CODE IDENTIFICATION
When a fault code is generated, the red brake
warning lamp will also illuminate. To determine
what the fault code is, momentarily ground the diag­
nostic connector and count the number of times the
antilock indicator lamp flashes. Fault codes and typ­
ical malfunctions are outlined in Figure 6.
The initial flash will be a long flash followed by a
number of short flashes. The long flash indicates the
beginning _ of the fault number sequence and the
short flashes are a continuation of that sequence.
You must count the long flash along with the
short flashes for an accurate fault code count.
CLEARING A FAULT CODE
To clear a fault code, disconnect the control module
connector or disconnect the battery for a minimum of
five seconds. During system retest, wait 30 seconds
to be sure the fault code does not reappear.
FAULT CONDITION CAUSES
RWA1 system faults can be generated by component
malfunction, or by the driver.
Component malfunctions will most frequently be
related to problems in the RWAL valve wire harness.
Look for loose connections, corroded terminals, dam­
aged wires, or loss of continuity due to connectors
filled with water or dirt. Blown circuit fuses and poor
ground connections are also common causes for sys­
tem faults. A misadjusted, or faulty stop lamp switch
will also cause a system fault.
Speed sensor and control module failures, although
infrequent, will be indicated by flash codes. The sen­
sor or module should not be replaced until diagnosis
indicates this is necessary.
The driver can induce system faults by riding the
brake pedal or leaving the parking brakes partially
applied. Either condition will cause the antilock