Chrysler Concorde 1993, Руководство по обслуживанию, Страница: 519 / 820

knock sensor detects a knock in one of the cylinders,
it sends an input signal to the PCM. In response, the
PCM retards ignition timing by a scheduled amount.
Knock sensors contain a crystal which constantly
vibrates and sends an input voltage (signal) to the
PCM while the engine operates. As the intensity of
the crystal’s vibration increase, the knock sensor out-
put voltage also increases.
IGNITION SENSE—PCM INPUT
The ignition sense input informs the powertrain
control module (PCM) that the ignition switch is in
the crank or run position.
MANIFOLD ABSOLUTE PRESSURE SENSOR—PCM
INPUT
The powertrain control module (PCM) supplies 5
volts to the MAP sensor. The MAP sensor converts
intake manifold pressure into voltage. The PCM
monitors the MAP sensor output voltage. As vacuum
increases, MAP sensor voltage decreases proportion-
ately. Also, as vacuum decreases, MAP sensor volt-
age increases proportionately.
During cranking, before the engine starts running,
the PCM determines atmospheric air pressure from
the MAP sensor voltage. While the engine operates,
the PCM determines intake manifold pressure from
the MAP sensor voltage. Based on MAP sensor volt-
age and inputs from other sensors, the PCM adjusts
spark advance and the air/fuel mixture.
On 3.3L engines the MAP sensor mounts to the
rear of the intake manifold plenum (Fig. 15). On
3.5L engines, the MAP sensor mounts to the drivers
side of the intake manifold plenum (Fig. 16). The
Map sensor must be in the horizontal position.
HEATED OXYGEN SENSORS—PCM INPUT
The fuel injection system uses two heated oxygen
sensors, one in the outlet of each exhaust manifold
(Fig. 17 or Fig. 18). Both sensors monitor the amount
of oxygen in the exhaust gas stream. The left sensor
monitors the odd numbered cylinders. The right sen-
sor monitors the even numbered cylinders.
The inputs from the oxygen sensors tell the power-
train control module (PCM) the oxygen content of the
exhaust gas. Based on the inputs from the two oxy-
gen sensors, the PCM fine tunes the air-fuel ratio in
each cylinder bank by adjusting injector pulse width.
The sensors produces from 0 to 1 volt, depending
upon the oxygen content of the exhaust gas in the
exhaust manifold. When a large amount of oxygen is
present (caused by a lean air-fuel mixture), the sen-
sors produce voltages as low as 0.1 volt. When there
is a lesser amount of oxygen present (rich air-fuel
mixture) the sensor produces a voltage as high as 1.0
volt. By monitoring the oxygen content and convert-
ing it to electrical voltage, the sensor acts as a rich-
lean switch.
The oxygen sensors are equipped with a heating el-
ement. The heating element keeps the sensor at
proper operating temperature during all operating
modes. Maintaining correct sensor temperature at all
times allows the system to enter into closed loop op-
Fig. 14 Knock Sensor Locations—3.5L Engine Only
Fig. 15 MAP Sensor—3.3L Engine
Fig. 16 MAP Sensor—3.5L Engine
14 - 26 FUEL SYSTEMS