1993 DODGE TRUCK Service Repair Manual

8E
- 4
INSTRUMENT PANEL
AND
GAUGES

•
MESSAGE CENTER—DIESEL
ENGINE

The message center (Fig. 7), which
is
located above
the Heater-A/C controls, includes warning lamps
for

the:

• brake systems (parking
and
service brakes)
• ABS brakes
• water
in
fuel
• wait
to
start (controlled
by Air
Heater Control
Module)
• Low Fuel.

BRAKE

CUMMINS
TURBO
DIESEL,

LOW
FUEL

DIESEL
FUEL ONLY WATER
IN
FUEL
WAIT
TO
START
J938E-55

Fig.
7
Message Center—Diesel Engine

ABS
WARNING LIGHT
This light monitors
the
ABS Brake System. This
light will come
on
when the ignition key
is
turned
to

the
ON
position
and may
stay
on for as
long
as

thirty seconds.
If
the ABS light remains
on or
comes
on during driving,
it
indicates that
the
ABS portion
of
the
brake system
is not
functioning. Refer
to
Group
5 -
Brakes
for
further information.
BRAKE
SYSTEM WARNING LIGHT

The Brake light
is
connected
to a
sensor that mon­
itors vacuum
in
the brake booster system. The Brake
light when
lit
indicates LOW VACUUM. The dual brake system provides
a
reserve braking
capability
in
the event
of a
failure
to a
portion
of
the
hydraulic system. Failure
of
either
of the
dual sys­
tem
is
indicated
by the
brake warning light which
will glow when
the
service brake pedal
is
depressed.
The light will remain
on
until
the
cause
is
corrected. The light will also come
on
when
the
parking
brake
is
applied with the ignition
in
the ON position. Refer
to
Group
5 -
Brakes
for
further information.

WATER
IN
FUEL
The Water
In
Fuel light
is
connected
to a
sensor lo­
cated
in the
fuel filter.
If
water collects
in the
fuel/
water separator filter,
the
Water
In
Fuel indicator
will light.

WAIT
TO
START
The Wait
To
Start light
is
connected
to a
sensor
that monitors intake
air
temperature
in the
intake
manifold.
If
intake
air
temperature
is low and
igni­
tion switch
is in
ON position,
the
PCM sends current
to
the
intake manifold
air
heaters
and the
Wait
To
Start light. This intake manifold preheat cycle
is

controlled
by an
electronic
Air
Heater Control Mod­

ule.
LOW FUEL
The Low Fuel light
is
connected
to a
sensor
in the

fuel tank. When the fuel level reaches approximately 1/6
of a
tank,
the
words LOW FUEL will illuminate
and remain
on
until fuel
is
added.

•

INSTRUMENT PANEL
AND
GAUGES
8E - 5
CLUSTER
AND
GAUGE TEST
PROCEDURES

INDEX
page
Fuel Gauge
Circuit
Test
9

Fuel Tank Sending
Unit
Test
5

Oil Pressure Gauge
Circuit
Test
..............
9
Sending
Unit
(Sensor) Test
5
page
Speedometer
10

Temperature
Gauge
Circuit
Test
8
Voltage Gauge
Circuit
Test
10

Warning Lamp System Tests
6

CAUTION:
Disconnect
battery
negative cable,
in
en­

gine compartment, before servicing instrument panel. When power
is
required
for
test purposes,
connect
battery
cable
(for
test only).

Disconnect battery negative cable after test
and before continuing service procedures.

SENDING
UNIT
(SENSOR) TEST
When
a
problem occurs with
a
cluster gauge,
be­

fore disassembling
the
cluster
to
check
the
gauge, check
for a
defective sending unit (sensor)
or
wiring.
(1) Sending units
and
wiring
can be
checked
by

grounding
the
connector leads,
at the
sending unit,
in
the
vehicle.

CAUTION:
When connecting
an
input
terminal
to

ground,
Do Not
leave
the
connection grounded
for
more than
a
few
seconds.

(2) With
the
ignition
in the ON
position;
a

grounded input will cause
the oil,
fuel
or
tempera­
ture gauge
to
read
at or
above maximum.
FUEL TANK SENDING
UNIT
TEST

(1) Disconnect wire from terminal
on
fuel tank
sending unit (Fig.
1).

FUEL PUMP SUPPLY
INPUT
TO
GAUGE
SENDING
UNIT
GROUND
FUEL PUMP GROUND
J928E-49

Fig.
1
Fuel
Tank
Sending
Connector
Terminals
(2) Connect wire
to a
known good sending unit.
(3) Connect
a
jumper wire between sending unit
fuel pick
up
tube
and a
good ground.
(4) Check fuel gauge
as
described
in
following

steps.
Allow
at
least three minutes
at
each test point
for gauge
to
settle. Lightly tapping instrument clus­
ter
may
help position pointer.

FUEL GAUGE SYSTEM DIAGNOSIS
FUEL GAUGE SYSTEM DIAGNOSIS FUEL GAUGE

DOES
NOT

READ
FULL FAULTY PRINTED
CIRCUIT BOARD FUEL GAUGE
INOPERATIVE OR ERRATIC FUEL GAUGE
INACCURATE

E

1

I

CHECK
FAULTY WIRING
OR
TANK DEFORMED
TANK
NOT
FULL COMPONENTS
CHECK
CHECK
ALL WIRING INCLUDING GROUND
i

FAULTY FUEL GAUGE SENDING
UNIT
i 1
FUEL
C
1
DOES
1
READ
1
pAUGE
I

>N0?
1

EMPTY
1

r

TANK
NOT
EMPTY
CHECK
PROPER
ALIGNMENT
OF PICKUP AND

SENDER
ASSEMBLY.

REFER
TO
GROUP
14
FAULTY FUEL
GAUGE

J908E-74

8E
- 6
INSTRUMENT PANEL
AND
GAUGES

•
(5)
Clip float arm of sending unit to its empty stop
(Fig. 2) and turn ignition key to ON position. The
gauge should read Empty, plus one pointer width, or
minus two pointer widths.
(6) Move and clip sending unit float arm to full

stop.
The gauge should read Full, or above.
Fig. 2 Fuel Tank Sending Unit Test
RESULTS (1) If fuel gauge does not meet specifications, check
following items as possible causes; (a) Wiring and connections between the gauge
sending unit and multiple connector. (b) Wiring and connections between multiple
connector and printed circuit board terminals.
(c) Circuit continuity between printed circuit
board terminals and gauge terminals.
If these items check okay, fuel gauge is defective
and must be replaced.
(2) If the fuel gauge meets specifications check fuel
tank and original installed fuel tank sending unit as follows:
(a) Carefully remove fuel tank sending unit from
tank.
(b) Connect sending unit wire and jumper wire
as described in the procedure.
(3) If fuel gauge now checks within specifications,
originally installed sending unit is electrically okay,
check following as possible cause:
(a) Ground strap from sending unit to fuel line
for continuity. (b) Sending unit deformed. Make sure sending
unit float arm moves freely and pick up tube is not
bent so that it contacts bottom of tank. Inspect float for any signs of damage or leaks. (c) Sending unit improperly installed. Install
properly.
(d) Mounting flange on fuel tank for sending
unit deformed. Feel for interference fit of sending
unit to bottom of tank. It is permissible to bend
pick up tube down a little near mounting flange to gain interference fit.
(e) Fuel tank bottom deformed causing improper
positioning of sending unit pick up tube. Replace or
repair tank and recheck sending unit. Refer to Fuel
Tank Section of Group 14 - Fuel System.

WARNING
LAMP
SYSTEM
TESTS
LOW
OH.
PRESSURE WARNING LAMP CIRCUIT
TEST
The low oil pressure warning lamp will illuminate
when the ignition key is turned to the ON position.
The lamp also illuminates if the engine oil pressure drops below a safe oil pressure level.
To test the system turn ignition key to the ON po­
sition.
If the lamp fails to light, inspect for a broken or
disconnected wire at the oil pressure combination
unit. The combination unit is located at the rear of
the engine (Fig. 3). If the wire at the connector checks good, pull connector loose from the switch and
with a jumper wire ground connector to the engine (Fig. 4). With the ignition key turned to the ON po­
sition check the warning lamp. If lamp still fails to
light, inspect for a burned out bulb or disconnected
socket in the cluster.
If light comes on, proceed and start engine. If the
lamp remains on, immediately turn engine off and
check engine oil pressure according to procedures as
outlined in Group 9 - Engine of this manual. If the
oil pressure meets specifications, check for a
grounded wire and/or replace the oil pressure send­
ing unit (refer to combination oil unit test). Fig. 3 Oil Pressure Sending Unit—Gas Engine

•

INSTRUMENT
PANEL
AND
GAUGES
8E - 7

STEERING PUMP
ENGINE
BLOCK
J9U9-74

Fig.
4 Oil
Pressure
Sending
Unit—Diesel
Engine
COMBINATION
OIL
UNIT
TEST
(FIG. 5)
The combination oil unit has 2 functions:
(1) The normal closed circuit keeps the oil pressure
warning lamp on until there is oil pressure. (2) The sending provides a resistance that varies
with oil pressure.
To test the normally closed oil lamp switch, discon­
nect the locking connector and measure the resis­
tance between the switch terminal and the metal
housing. The ohmmeter should read 0 ohms. Start
the engine.
If there is oil pressure, the ohmmeter should read
an open circuit. To test the sending unit, measure the resistance
between the sending unit terminal and the metal
housing. The ohmmeter should read open, Start the engine.
The ohmmeter should read between 30 to 55 ohms,
depending on engine speed, oil temperature, and oil
viscosity.
If the previous results are not obtained, replace the
switch.

SEAT
BELT
WARNING
SYSTEM
For testing of this system refer to Section 8M -
Seat Belt Warning Systems.

BRAKE
SYSTEM
WARNING
LAMP
(FIG. 6) The brake warning lamp illuminates when the
parking brake is applied with the ignition key
turned ON. The same lamp will also illuminate should one of the two service brake systems fail
when the brake pedal is applied. To test the system
turn the ignition key ON, and apply the parking
brake. If the lamp fails to light, inspect for a burned
out bulb, disconnected socket, a broken or discon-
ENGINE WARNING LAMP DIAGNOSIS
OIL PRESSURE
FUNCTION

TURN

IGNITION

SWITCH
"OH"
(DO NOT
ISTART ENGINE)! LAMP "OFF'
LAMP "ON"
DEFECTIVE BULB START AND IDLE
ENGINE
BULB SOCKET OR WIRING OPEN LAMP STAYS
"ON" TURN OFF
ENGINE LAMP GOES
"OFF" DEFECTIVE
SWITCH CHECK FOR
GROUNDED WIRING
WARNING
LIGHT
OK CHECK FOR
LOW OIL LEVEL
ENGINE OIL
PRISSURi
LOW
REFER TO
ENGINE SERVICE DIAGNOSIS ENGIM

PRES
0
IE OIL
1

SURE
1
,K I

DEFECTIVE SWITCH TEST ENGINE
OIL PRESSURE

PR1448C

SWITCH
(LIGHT)
SENDING
UNIT

(GAUGE)

898E-2

Fig.
5 Combination Oil Unit Terminals
nected wire at the switch. The lamp also lights when
the ignition switch is turned to the START position. To test the service brake warning system,
(1) Raise the vehicle on a hoist.
(2) Open a wheel cylinder bleeder while a helper

8E
- 8 INSTRUMENT PANEL AND GAUGES

•

BRAKE

WARNING
LAMP
SWITCH TO BRAKE
WARNING LAMP

PR!
451

Fig.
6
Brake Warning
Lamp
Switch
depresses
the
brake pedal
and
observes
the
warning

lamp.

If
the
lamp fails
to
light, inspect
for:

•
a
burned
out
bulb
• disconnected socket
•
a
broken
or
disconnected wire
at the
switch. If
the
bulb
is not
burned
out and the
wire continu­
ity
is
proven, replace
the
brake warning switch.
The

switch
is in the
brake line
Tee
fitting mounted
on

the frame rail
in the
engine compartment below
the

master cylinder.

CAUTION:
If
wheel cylinder bleeder
was
opened

check
master cylinder fluid level.

On Diesel Models
The
Brake light
is
also con­
nected
to a
sensor that monitors vacuum
in the

brake booster system.
The
Brake light when
lit
indi­ cates
LOW
VACUUM. Refer
to
Group
5 -
Brakes
for

more information.

TEMPERATURE
GAUGE CIRCUIT TEST
(1) Remove temperature gauge. Refer
to
Gauge
Re­

placement. (2) Check continuity
in the
wire between
the
tem­
perature sensor
and the
temperature gauge (sensor
input
pin)
(Figs.
7, 8 and 9).
(3) With
the
ignition switch
in the ON
position,
check
for
battery voltage across
the B + pin and the

Ground
pin.
(TURN
IGNITION
KEY
"ON"

(DO
NOT
START
ENGINE

I
RELEASE
PARKING
BRAKE)
I

I

[
WARNING
LIGHT
GOES
I
"ON"
I

1
(LIGHT
SHOULD
BE
"OFF")!
X

APPLY PARKING BRAKE (WARNING
LIGHT

SHOULD
GO "ON")

BRAKE
SYSTEM
LEAKING FLUID
X

WARNING
LIGHT

FAILS
TO GO "ON" GROUNDED WIRING
BULB
BURNED
OUT

SHORTED PARKING BRAKE
OR BRAKE WARNING SWITCH

X
DISCONNECTED
OR
FAULTY

BULB
SOCKET
FAULTY BRAKE SYSTEM PROPORTIONING VALVE
UNIT*
BROKEN
WIRE
OR
WIRE
DISCONNECTED
AT
PARKING
BRAKE
SWITCH

X

FAULTY PARKING
BRAKE
SWITCH

X

APPLY SERVICE BRAKES
(WARNING
LIGHT

SHOULD
NOT GO "ON")

JZ
X

TEST SERVICE BRAKE WARNING
SYSTEM FUNCTION*

X
WARNING
LIGHT
GOES

"ON"

WARNING
LIGHT

DOES
NOT GO "ON"
BRAKE
SYSTEM
LEAKING FLUID
OPEN CIRCUIT
IN
WIRING
TO SERVICE BRAKE SWITCH
X

GROUNDED WIRING
OR

SHORTED BRAKE WARNING SWITCH

LOOSE
BULKHEAD CONNECTOR
X

FAULTY BRAKE SYSTEM
PROPORTIONING VALVE
UNIT*

FAULTY SERVICE BRAKE SWITCH

X
•TESTS
ARE
DESCRIBED
IN APPROPRIATE
SECTION
OF
SERVICE MANUAL
FAULTY SERVICE BRAKE
SYSTEM PROPORTIONING VALVE
UNIT*
PR1449A

INSTRUMENT
PANEL
AND
GAUGES
8E - S
J938E-34
Fig. 7 Coolant Temperature Sensor—Gas Engine
AIR
TEMPERATURE SWITCH

-
COOLANT TEMPERATURE
SWITCH

Fig. 8 Coolant Temperature Sensor—Diesel Engine

OIL PRESSURE
GAUGE
CIRCUIT
TEST
(1) Remove oil pressure gauge. Refer to Gauge Re­
placement. (2) Check for continuity in the wire between the
oil pressure sensor and the oil pressure gauge (sensor
input pin) (Figs. 10, 11, 12 and 13). (3) With the ignition switch in the ON position,
check for battery voltage across the B+ pin and the Ground pin. J908E-6i_
Fig. 9 Temperature Gauge Pins

TEMPERATURE/OIL/FUEL
GAUGE
DIAGNOSIS

GAUGE INDICATES HIGHER

OR
LOWER
THAN
ACTUAL I
FAULTY WIRING
FAULTY SENDING
UNIT*

FAULTY INSTRUMENT PANEL
GAUGE*
ERRATIC
GAUGE OPERATION
'TEST

PROCEDURES

DESCRIBED

ARE
IN
APPROPRIATE
SECTION OF

SERVICE

MANUAL

LOOSE
OR DIRTY ELECTRICAL CONNECTIONS FAULTY INSTRUMENT PANEL
GAUGE*
J908E-52

FUEL
GAUGE
CIRCUIT
TEST
(1) Remove fuel gauge assembly. Refer to Gauge
Replacement. (2) Check for continuity in the wire between the
fuel tank sending unit and the gauge (fuel level in­
put pin) (Figs. 14 and 15). (3) With the ignition switch in the ON position,
check for battery voltage across the B + pin and the Ground pin.

8E
- 10
INSTRUMENT
PANEL
AND
GAUGES

GROUND
OIL
PRESSURE

SENSOR
INPUT

J908E-70

Fig.
10 Oil Pressure
Sending
Unit—Gas Engine

STEERING
PUMP
ENGINE
BLOCK

J9119-74

Fig.
11 Oil Pressure
Sending
Unit—Diesel Engine
SENDING
UNIT
(GAUGE)

SWITCH
(LIGHT)
898E-2

Fig.
12 Combination Oil Unit Terminals

VOLTAGE
GAUGE
CIRCUIT
TEST
(1) Remove voltage gauge. Refer to Gauge Replace­
ment.
Fig.
13 Oil Pressure
Gauge
Pins

r— FUEL
PUMP
SUPPLY

0 INPUT TO
GAUGE
-SENDING
UNIT
GROUND

-FUEL
PUMP
GROUND
J928E-49

Fig.
14 Fuel Tank
Sending
Connector Terminals

FUEL
GAUGE
INPUT

^
GROUND
y
J908E-71

Fig.
15 Fuel
Gauge
Pins

(2) With the ignition switch in the ON position,
check for battery voltage across the B+ pin and the Ground pin (Fig. 16).
The instrument panel voltmeter indicates elec­
trical system battery voltage.

SPEEDOMETER
(1) Remove speedometer assembly. Refer to Gauge
Replacement.

•

Fig.
16
Voltmeter
Pins

(2) Check for continuity in the wire between the
distance sensor connector and the speedometer (dis­
tance sensor input pin) (Fig. 17).
(3) With the ignition switch in the ON position,
check for battery voltage across the B + pin and the Ground pin. —
INSTRUMENT PANEL
AND
GAUGES
8E - 11

Fig.
17 Speedometer
Pins
(4) Perform distance sensor test. Refer to General
Information - Distance Sensor in this section.

(5)
If all previous tests prove good, replace speed­
ometer.