Dodge RAM TRUCK 1500 1995 Service Manual page 380

B R
IGNITION SYSTEMS 80 • 7
POWERTRAIN CONTROL
MODULE (PCM) J9414-11
Fig. 15 PCM Location—Typical
shut off positive voltage to all of the coils. Coil oper­
ation (firing) is then controlled by switching ground
circuits (off-and-on) through the PCM. The PCM will
determine cylinder identification after receiving sig­
nals from the crankshaft and camshaft position sen­
sors.
Ignition coil ground path circuits for paired cylin­
ders number 1/6, 3/2 and 9/8 are operated by the
PCM only.
A separate ignition control module (1CM), along
with commands from the PCM, is used to control the
ground path circuits for only two of the five paired
coil packs. This will be for paired cylinders number
4/7 and 5/10. The ICM is located in the engine com­
partment. It is mounted to the right inner fender be­
hind the coolant reserve/overflow tank (Fig. 16).
COOLANT
RESERVE/OVERFLOW
SOLTS (2) J948D-21
Fig. 16 ignition Control Module Location—S.OL V-10
Engine
Base ignition timing is not adjustable on t h e
8.0L ¥-1© engine. By controlling all of the coil
ground circuits, the PCM is able to set the base tim­
ing and adjust the ignition timing advance. This is
done to meet changing engine operating conditions.
The PCM adjusts ignition timing based on Inputs it
receives from:
• The engine coolant temperature sensor
• The crankshaft position sensor (engine speed)
• The manifold absolute pressure (MAP) sensor
• The throttle position sensor
• Transmission gear selection
For component testing, refer to the Diagnostics/Ser­
vice Procedures section of this group.
For removal and installation of the coil packs, refer
to the Component Removal/Installation section of
this group.
IGNITION CONTROL MODULE—8.0L V-10 ENGINE
MODULE OPERATION
For ignition control module (ICM) operation, refer
to the previous section on Ignition Coil Packs—-8.OL
V-10 Engine.
For ICM testing, refer to the appropriate Power-
train Diagnostic Procedures manual for operation of
the DRB scan tool.
For removal and installation of the ICM, refer to
the Component Removal/Installation section of this
group.
ENGINE COOLANT TEMPERATURE SENSOR
For an operational description, diagnosis and re­
moval and installation procedures, refer to Group 14,
Fuel System.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
For an operational description, diagnosis and re­
moval and installation procedures, refer to Group 14,
Fuel System.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
For information, refer to Group 14, Fuel System.
POWERTRAIN CONTROL MODULE (PCM)
The powertrain control module (PCM) is located in
the right-rear side of the engine compartment (Fig.
15). The PCM was formerly referred to as the SBEC
or engine controller.
The ignition system is controlled by the PCM.
Base ignition timing (by rotation of distribu­
tor) is not adjustable.
The PCM opens and closes the ignition coil ground
circuit to operate the ignition coil (or coils). This is
done to adjust ignition timing, both initial (base) and
advance, for changing engine operating conditions.
The PCM adjusts ignition timing based on inputs it
receives from:
• The engine coolant temperature sensor
© The crankshaft position sensor (engine speed)
• The manifold absolute pressure (MAP) sensor
• The throttle position sensor
® Transmission gear selection