Chrysler RAM TRUCK 2500 1994 Service Manual page 366

• IGNITION SYSTEMS 80 - 9
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
For information, refer to Group 14, Fuel System.
POWERTRAIN CONTROL MODULE (PCM)
The powertrain control module (PCM) is located i n
the right-rear side of the engine compartment (Fig.
22). 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 i t
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 removal and installation of this component, re­
fer to the Component Removal/Installation section of
this group.
For diagnostics, refer to the appropriate Powertrain
Diagnostic Procedures service manual for operation
of the DRB scan tool.
POWERTRAIN CONTROL
MODULE (PCM) J9414.11
Fig. 22 PCM Location—Typical
OXYGEN SENSOR (02S)
For an operational description, diagnosis and re­
moval or installation of the 02S, refer to Group 14,
Fuel Systems i n this manual.