Chrysler RAM TRUCK 2500 1994 Service Manual page 410

INSTRUMENT PANEL AND GAUGES 8E - 13
WARNING LAMP SYSTEM TESTS
BRAKE SYSTEM WARNING LAMP
The brake warning lamp illuminates when the
parking brake is applied with the ignition switch
turned ON. The same lamp will also illuminate
should one of the two service brake systems (RWAL
or ABS) fail when the brake pedal is applied. Refer to
Group 5 - Brakes for diagnosis of these components.
The lamp also lights when the ignition switch is
turned to the START position, as a bulb check.
Diesel Models — The brake warning lamp is
also connected to a sensor that monitors vac­
uum i n the brake booster system. O n these
models, an illuminated brake warning lamp can
also indicate a low vacuum condition. Refer to
Group 5 - Brakes for more information.
I f brake warning lamp fails to light during bulb
check (ignition switch i n START position), proceed as
follows:
(1) Pull instrument cluster from dash. Do not un­
plug cluster connectors. Refer to Instrument Cluster
Replacement for removal procedures.
The bulb location is labeled on the cluster
printed circuit board. Refer to Group 8W - Wir­
ing Diagrams for more information.
(2) Replace brake warning lamp bulb with a
known good unit. Check for lamp operation by turn­
ing ignition switch to START position. I f OK, rein­
stall cluster. I f not OK, continue to next step.
(3) Turn ignition switch to ON position. Check for
battery voltage at B+ terminal of bulb. I f OK, go to
step (5). I f not OK, continue to next step.
(4) Unplug cluster connector B (black). With igni­
tion switch i n ON position, check for battery voltage
at connector cavity #8. I f OK, replace cluster printed
circuit board. I f not OK, repair open circuit to fuse
#12 as required.
(5) Disconnect battery negative cable. Hold ignition
switch i n START position while checking for continu­
ity to ground at ground terminal of bulb. I f OK, re­
place bulb. I f not OK, continue to next step.
(6) Unplug cluster connector A (white). Hold igni­
tion switch in START position while checking connec­
tor cavity #4 for continuity to ground. I f OK, replace
cluster printed circuit board. I f not OK, repair open
ground circuit from ignition switch.
I f brake warning lamp lights during bulb check,
but does not light to indicate a brake system mal­
function, check the circuit as follows:
• from ground terminal at bulb to cluster connector
A, cavity #5.
• from cluster connector A, cavity #5 to splice joint
connector C. Refer to Group 8W - Wiring Diagrams
for more information.
• from splice joint connector C, check the suspected
faulty switch and its circuit. Also see Group 5 -
Brakes for additional information.
LOW OIL PRESSURE
Refer to Oil Pressure Gauge Diagnosis
FOUR-WHEEL DRIVE
The four-wheel drive indicator lamp should illumi­
nate any time the front axle disconnect is connected
(engaged) in the four-wheel drive mode. I f the indica­
tor lamp bulb is good, check the circuit from the in­
strument cluster to the switch. Refer to Group 2 -
Front Suspension and Axle for more information.
(1) Pull instrument cluster from dash. Do not un­
plug cluster connectors. Refer to Instrument Cluster
Replacement for removal procedures.
The bulb location is labeled on the cluster
printed circuit. Refer to Group 8W - Wiring Di­
agrams for more information.
(2) With transfer case shifted to a four-wheel drive
mode, turn ignition switch to ON position. Check for
battery voltage between B+ terminal and ground ter­
minal of bulb. I f OK, replace bulb. I f not OK, con­
tinue to next step.
(3) With ignition switch i n ON position, check for
battery voltage between B+ terminal of bulb and a
known good ground. I f OK, go to step (5). I f not OK,
continue to next step.
(4) Unplug cluster connector B (black). With igni­
tion switch in ON position, check for battery voltage
at connector cavity #8. I f OK, replace cluster printed
circuit board. I f not OK, repair open circuit to fuse
#12 as required.
(5) With ignition switch i n OFF position, check for
continuity between ground terminal of bulb and clus­
ter connector B (black), cavity #13. There should be
continuity. I f OK, continue to next step. I f not OK,
replace cluster printed circuit board.
(6) Check for continuity from cluster connector B
(black), cavity #13 to switch at front axle disconnect
housing. I f not OK, repair circuit as required. I f OK,
refer to Group 2 - Front Suspension and Axles and/or
Group 21 - Transmission and Transfer Case for diag­
nosis of four-wheel drive axle disconnect and con­
trols.
MALFUNCTION INDICATOR (CHECK ENGINE) -
(1) Pull instrument cluster from dash. Do not un­
plug cluster connectors. Refer to Instrument Cluster
Replacement for removal procedures.
The bulb location is labeled on the cluster
printed circuit. Refer to Group 8W - Wiring Di­
agrams for terminal information.
(2) Check for battery voltage between bulb B+ and
ground terminals within 3 seconds after turning igni­
tion switch to ON position. I f OK, replace bulb. I f not
OK, continue to next step.