Sistema combustible

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C1388C (X3) Connector: Power, Ground,
Relay Control and Communications
C1388B (X2) Connector: Injector Control, Cyl. 2,3,5,8
C1388A (X1) Connector: Injector Control, Cyl. 1,4,6,7
C1388A

FICM DESCRIPTION AND BASIC OPERATION
A drawing of the FICM (Fuel Injection Control Module) subsystem is shown in Figure 1.
The FICM drives the fuel injector solenoids based on fuel and timing commands(via *CAN2 link) from the PCM. It
uses engine speed and position signals (*CKPO, *CMPO) to determine when the injectors need to be activated.
The ignition switch provides *KEYPWR to the FICM. Once this signal is detected by the FICM, the *MPR output of
the FICM will engage the FICM relay. This in turn provides the *FICM PWR and *FICM Logic PWR voltages to the
FICM.
The FICM provides a feedbacksignal to the PCM indicating when the FICM is providing control signals to the
injector (fueling) (via CAN2 link and *FICMM signal).
The FICM will cycle through the injector outputs when the key is placed in the ON position. This is called pre-cycle
and the time of pre-cycle varies with engine temperature. The pre-cycle is done as a self test of the injector
circuits.
*See Glossary fordetailed definition or explanation.

PCM

FICM

CAN2H

Injectors

CAN2L
Cyl 1
CAN2 SHD
Cyl 4

CKPO
Sensors &
Actuators

C1388A (X1)

CMPO

Cyl 6
FICMM
Cyl 7
Ignition Switch

C1388C (X3)

Keypwr (VPWR)
Cyl 2
FICM Logic Pwr
FICM Power
Relay
12V
Electrical
System

+

Cyl 3
10 Amp
fuse

C1388B (X2)

FICM Pwr

Cyl 5

MPR
Cyl 8

-

FICM Pwr GndInjector Shield

Figure 1

1
2

FICM DESCRIPTION AND BASIC OPERATION (CONT’D)
The internal structure of the FICM is shown in Figure 2.The FICM internally generates 48V used to drive the injector
solenoids.
See Figure 3 for diagram of output configuration. Each individual injector is controlled with four driver outputs from
the FICM. There are high and low side drivers for the open and closecoil of each injector.
On 2004.25+ (1845117C2 FICMs), the low side driver is actually shared among 4 injectors. This means an injector
short to ground on the low side could produce four different cylinder error codes. On 2003.25 (1837127C4 FICMs)
there are individual low side drivers for each injector. This means a low side failure would result in a single injector
error code. Note:International FICM part numbers are located on a label on the connector side of the module.

FICM Pwr

48 Volt Injector
Supply

10 Amp

FICM
Logic Pwr

5V Supply

Key PWR
(VPWR)
CAN2H
CAN2L

Injector Control

To
Injectors

Microprocessor

CMPO
CKPO
FICMM

Relay
Control

To MPR

To FICM
PWR GND

Figure 2

2

Injector Control
48V
Injector High
Side Driver
(OpenCoil)

Injector Solenoid
(Open Coil)

Injector Low
Side Driver
(Open Coil)

Microprocessor
Control

48V
Injector High
Side Driver
(Close Coil)

Injector Solenoid
(Close Coil)

Injector Low
Side Driver
(Close Coil)

Figure 3

3

3

FICM DESCRIPTION AND BASIC OPERATION (CONT’D)
To drive the fuel injector, the FICM produces two control signals for each injector.
Theopen coil is driven (via a 20A pulse) to open the injector. This shifts the spool valve in the injector to the open
state. Once this has taken place, high pressure oil is directed on top of the injector intensifier piston. In result, fuel
is being delivered through the nozzle of the injector.
Once the desired fuel has a been delivered, as calculated by the PCM/FICM, the close coil is driven (viaa 20A
pulse) to close the injector. This stops the distribution of high pressure oil to the top of the intensifier piston thus
stopping the delivery of fuel.
The net time between pulses is equivalent to the fuel pulse width (FuelPW) used to provide fueling.
The coil on time is currently calibrated from “400us to 5.8ms”. The 5.8ms is for cold starts. As the engine warms up
the duration...
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