Dodge RAM TRUCK 1500 1995 Service Manual page 1177

- COMPONENT DESCRIPTION/SYSTEM OPERATION—DIESEL ENGIIH U - SS
mm
Fig.' 13 Check Engine Lamp—Typical Location
If the powertrain control module (PCM) receives an
incorrect signal, or no signal from certain sensors or
components, the lamp is turned on. This is a warning
that the PCM has recorded a system or sensor mal­
function. It signals an immediate need for service.
The lamp can also be used to display a diagnostic
trouble code (DTC). Cycle the ignition switch On-Off-
On-Off-On within three seconds and any codes stored
in the PCM memory will be displayed. This is done
in a series of flashes representing digits. Refer to On-
Board Diagnostics in the General Diagnosis section
of this group for more information.
SPEED CONTROL—PCM PINS #33 AND #53—PCM
OUTPUT
These two circuits control vent and vacuum opera­
tion of the speed control solenoids.
AIR CONDITIONING RELAY—PCM PIN #34—PCM
OUTPUT
This circuit controls a ground signal for operation
of the A/C clutch relay. Also refer to Air Conditioning
(A/C) Controls-PCM Pin #27-PCM Input for addi­
tional information.
The A/C relay is located in the power distribution
center (PDC). The PDC is located next to the battery
in the engine compartment (Fig. 14). For the location
of the relay within the PDC, refer to PDC cover.
WATER-IN-FUEL WARNING LAMP—PCM PIN
#35—PCM INPUT
The PCM turns the water-in-fuel indicator lamp to
the ON position if water is detected in the fuel. The
water-in-fuel indicator lamp is located in the instru­
ment panel (Fig. 15). The lamp will illuminate for
about two seconds each time the ignition key is ini­
tially turned to the ON position as a bulb check.
Also refer to Water-ln-Fuel Sensor—PCM Pin #1 —
PCM Input for additional information.
Fig. 14 Power Distribution Center (PDC) Location
WAIT-TO-
START
WARNING LAMP
HEAT-A/C
TEMPERATURE
' CONTROL
KNOB
WARNING LAMP WARNING LAMP J9414-63
Fig. 15 Wait-to-Start and WateNn-Fuel Warning
Lamp Location
WAIT-TO-START LAMP WARNING LAMP—PCM
PIN #36—PCM OUTPUT
The wait-to-start warning lamp is turned on and
off by the PCM based on the intake manifold air tem­
perature sensor input. The lamp is located on the in­
strument (Fig. 15).
The lamp is turned on when the ignition is first ac­
tivated. If the PCM reads intake manifold air tem­
perature below 15°C (59°F), it will turn the wait-to-
start warning lamp on for the air heater preheat
cycle. The lamp stays on until the preheat cycle is
over.
The wait-to-start lamp will flash on and off if the
intake manifold air temperature sensor input to the