Dodge Dakota (R1). Manual - part 294
A/C REQUEST SIGNAL: When either the A/C or
Defrost mode has been selected and the A/C low and
high–pressure switches are closed, an input signal is
sent to the ECM. The ECM uses this input to cycle
the A/C compressor through the A/C relay.
If the A/C low or high–pressure switch opens, the
ECM will not receive an A/C request signal. The
PCM will then remove the ground from the A/C relay.
This will deactivate the A/C compressor clutch. Also,
if the engine coolant reaches a temperature outside
normal of its normal range, or it overheats, the ECM
will deactivate the A/C clutch.
This circuit controls a ground signal for operation
of the A/C clutch relay. Also refer to Air Conditioning
(A/C) Controls—ECM Input for additional informa-
tion.
The A/C relay is located in the Power Distribution
Center (PDC). The PDC is located next to the battery
in the engine compartment. For the location of the
relay within the PDC, refer to label on PDC cover.
DESCRIPTION-NEEDLE MOVEMENT OR
INSTRUMENTED FIRST INJECTOR—ECM
INPUT
This input from the ECM supplies a constant 30
mA electrical current source for the first injector sen-
sor. It will vary the voltage to this sensor when it
senses a mechanical movement within the injector
needle (pintle) of the number–1 cylinder fuel injector.
When this voltage has been determined by the ECM,
it will then control an output to the fuel timing sole-
noid (the fuel timing solenoid is located on the fuel
injection pump). Also refer to Fuel Injection Pump for
additional information.
The first injector sensor is a magnetic (inductive)
type.
The first injector sensor is used only on the fuel
injector for the number–1 cylinder (Fig. 2). It is not
used on the injectors for cylinders number 2, 3, or 4.
DESCRIPTION-POWER GROUND
Provides a common ground for power devices (sole-
noid and relay devices).
DESCRIPTION-IGNITION CIRCUIT SENSE—
PCM INPUT
The ignition circuit sense input signals the PCM
that the ignition (key) switch has been turned to the
ON position. This signal initiates the glow plug con-
trol routine to begin the “pre–heat” cycle.
DESCRIPTION-IGNITION CIRCUIT SENSE—
ECM/PCM INPUT
The ignition circuit sense input signals the ECM
and PCM that the ignition (key) switch has been
turned to the ON position. This signal initiates the
glow plug control routine to begin the “pre–heat”
cycle.
DESCRIPTION-SENSOR RETURN—ECM/PCM
INPUT (ANALOG GROUND)
Sensor Return provides a low noise Analog ground
reference for all system sensors.
DESCRIPTION-BATTERY VOLTAGE—PCM
INPUT
The battery voltage input provides power to the
PCM. It also informs the PCM what voltage level is
being supplied by the generator once the vehicle is
running.
The battery input also provides the voltage that is
needed to keep the PCM memory alive. The memory
stores Diagnostic Trouble Code (DTC) messages.
Trouble codes will still be stored even if the battary
voltage is lost.
Fig. 2 Fuel Injector Sensor
1 - NEEDLE MOVEMENT SENSOR
2 - FUEL INJECTOR (NUMBER 1 CYLINDER ONLY)
3 - COPPER WASHER
4 - SENSOR CONNECTOR
8Ea - 2
ELECTRONIC CONTROL MODULES
R1
ENGINE CONTROL MODULE (Continued)