Dodge RAM TRUCK 1500 1995 Service Manual page 1176

14 -14 COMPONENT DESCRIPTION/SYSTEM OPERITIOI—DIESEL ENGINE
Fig. 10 Engine Speed Sensor—Diesel
POWERTRAIN CONTROL
MODULE (PCM) J9414-11
Fig. 11 PCM and Data Link Connector—Typical
high-pressure switches are closed, an input signal is
sent to the powertrain control module (PCM). The
PCM uses this input to cycle the A/C compressor
through the A/C relay.
If the A/C low or high-pressure switch opens, the
PCM will not receive an A/C request signal. The
PCM will then remove the ground from the A/C relay.
This will deactivate the A/C compressor clutch.
BRAKE SWITCH—PCM PIN #29—PCM INPUT
When the brake light switch is activated, the pow­
ertrain control module (PCM) receives an input indi­
cating that the brakes are being applied. After
receiving this input, the PCM is used to control the
speed control system and electrical operation of the
transmission torque converter.
PARK/NEUTRAL SWITCH—PCM PIN #30—PCM
INPUT
The park/neutral switch provides an input to the
powertrain control module (PCM). This will indicate
that the automatic transmission is in Park, Neutral
or a Drive gear selection. This input is used to deter­
mine speed control strategy and electrical operation
of both the overdrive and torque convertor solenoids.
Refer to Group 21, Transmissions, for testing, re­
placement and adjustment information.
TRANSMISSION TEMPERATURE WARNING
LAMP—PCM PIN #31—PCM OUTPUT
AUTOMATIC TRANSMISSION OMLY
An instrument panel mounted lamp (Fig. 12) is
used to warn of a possible transmission fluid over­
heating condition. When transmission fluid tempera­
ture has been determined to be above approximately
280 degrees F by the transmission temperature sen­
sor, a signal is sent to the powertrain control module
(PCM). The PCM will then control warning lamp op­
eration. The lamp will illuminate for about two sec­
onds each time the ignition key is initially turned to
the ON position as a bulb check.
Also refer to Transmission Temperature Sensor—
PCM Pin #42-PCM Input for additional informa­
tion.
INSTRUMENT
Fig. 12 Transmission Temperature Warning
Lamp—Typical Location
MALFUNCTION INDICATOR LAMP—PGM PIN
# 3 2 — P C M
OUTPUT
The malfunction indicator lamp illuminates on the
instrument panel each time the ignition key is
turned on. This lamp is displayed on the instrument
panel as the CHECK ENGINE lamp (Fig. 13). Note
that the lamp will illuminate for approximately two
seconds each time the key is initially turned to the
ON position. This feature is used as a bulb check.