Dodge ZB 2005, Руководство по обслуживанию

Страница: 799 / 1873

The PCM adjusts injector pulse width by opening
and closing the ground path to the injector. Engine
RPM (speed) and manifold absolute pressure (air
density) are the primary inputs that determine
injector pulse width.
OPERATION - MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does for
Wide Open Throttle (WOT). There are several differ-
ent modes of operation that determine how the PCM
responds to the various input signals.
There are two different areas of operation, OPEN
LOOP and CLOSED LOOP.
During OPEN LOOP modes the PCM receives
input signals and responds according to preset PCM
programming. Inputs from the upstream and down-
stream heated oxygen sensors are not monitored dur-
ing OPEN LOOP modes, except for heated oxygen
sensor diagnostics (they are checked for shorted con-
ditions at all times).
During CLOSED LOOP modes the PCM monitors
the inputs from the upstream and downstream
heated oxygen sensors. The upstream heated oxygen
sensor input tells the PCM if the calculated injector
pulse width resulted in the ideal air-fuel ratio of 14.7
to one. By monitoring the exhaust oxygen content
through the upstream heated oxygen sensor, the
PCM can fine tune injector pulse width. Fine tuning
injector pulse width allows the PCM to achieve opti-
mum fuel economy combined with low emissions.
For the PCM to enter CLOSED LOOP operation,
the following must occur:
(1) After the engine is started, the closed loop
timer must count down to zero. The engine coolant
temperature must be over 0F for the closed loop
timer to initiate. The following start up coolant tem-
peratures are used to determine the closed loop timer
start time.
•
If the coolant is over -4F the PCM will wait 100
seconds.
•
If the coolant is over 14F the PCM will wait 70
seconds.
•
If the coolant is over 45F the PCM will wait 45
seconds.
•
If the coolant is over 63F the PCM will wait 25
seconds.
(2) For other temperatures the PCM will interpo-
late the correct waiting time.
(3) O2 sensor voltage must stay below ~1.02 Volts.
(4) The engine is NOT in decel fuel shut-off or
WOT mode.
(5) The engine speed is below 3808 RPM.
The multi-port fuel injection systems has the fol-
lowing modes of operation:
•
Ignition switch ON (Zero RPM)
•
Engine start-up
•
Engine warm-up
•
Cruise
•
Idle
•
Acceleration
•
Deceleration
•
Wide Open Throttle
•
Ignition switch OFF
The engine start-up (crank), engine warm-up,
deceleration with fuel shutoff and wide open throttle
modes are OPEN LOOP modes. Under most operat-
ing conditions, the acceleration, deceleration (with
A/C on), idle and cruise modes, with the engine at
operating temperature are CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
•
The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input. The
PCM determines basic fuel injector pulse width from
this input.
•
The PCM determines atmospheric air pressure
from the MAP sensor input to modify injector pulse
width.
When the key is in the ON position and the engine
is not running (zero rpm), the Auto Shutdown (ASD)
and fuel pump relays de-energize after approximately
1 second. Therefore, battery voltage is not supplied to
the fuel pump, ignition coil, fuel injectors, upstream
O2 sensor heaters, and hydraulic fan module.
ENGINE START-UP MODE
If the clutch pedal is depressed, the starter button
energizes the starter relay. The following actions
occur when the starter motor is engaged.
•
If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the Auto Shutdown (ASD) relay and fuel pump relay.
If the PCM does not receive both signals within
approximately one second, it will not energize the
ASD relay and fuel pump relay. The ASD and fuel
pump relays supply battery voltage to the fuel pump,
fuel injectors, ignition coil, (EGR solenoid and PCV
heater if equipped) and heated oxygen sensors.
•
The PCM energizes the injectors (on the 69°
degree falling edge) for a calculated pulse width until
it determines crankshaft position from the camshaft
position sensor and crankshaft position sensor sig-
nals. The PCM determines crankshaft position within
1 engine revolution.
14 - 26 FUEL INJECTION
ZB
FUEL INJECTION (Continued)