Innova 3120d, Owner'S Manual, Page: 61 / 131

Chrysler/Jeep OBD1 Systems
CHRYSLER/JEEP OBD1 SYSTEMS
3120d 59
CHRYSLER/JEEP OBD1 SYSTEMS
Chrysler Motors On-Board Computer Systems
Chrysler Motors introduced its first electronic fuel injected vehicle in late
1983. The on-board computer management systems used on Chrysler
vehicles have evolved over the years, and their names have changed
accordingly.
1983-87: The on-board computer used in these vehicles is a split-
system, composed of two separate units: the Logic Module and the
Power Module. The Logic Module contains a microprocessor which
processes data received from sensors located throughout the vehicle
and makes decisions (based on these inputs) which effect engine
operation. The Logic Module is usually located on the right-hand side,
behind the kick panel. The Power Module supplies operating power to
the Logic Module, and contains the circuits which control the high-
current devices. Power Module operation is controlled by the Logic
Module. The Power Module is located in the engine compartment, near
the vehicle’s battery.
1987-90: This system is called a Single Module Engine Controller
(SMEC). This system still uses two separate circuit boards (Logic
Module and Power Module). However, both circuit boards are located in
a common enclosure.
1989-95: This system is called a Single Board Engine Controller
(SBEC). On this system, the Logic Module and Power Module circuit
boards are integrated on a single circuit board.
1993-97: Beginning in 1993, the computer was renamed the
Powertrain Control Module (PCM). In addition to controlling the engine
management system and emission system, the computer also takes
an active role in controlling powertrain (transmission system)
operation.
Unless otherwise specified, all references to “computer” within
this manual also apply to “Logic Module/ Power Module”,
“SMEC”, “SBEC” or “PCM”.
Jeep On-Board Computer Systems
1993-95: In 1993, Jeep on-board computer systems (fuel injected
vehicles only) were converted to the Chrysler on-board computer
systems. All 1993 through 1995 fuel injected Jeep and Chrysler vehicles
are equipped with similar on-board computer systems.