Chrysler PT Cruiser Service & Repair Manual page 321

PT
POWERTRAIN CONTROL MODULE (Continued)
• Coolant temperature
• Exhaust gas content (oxygen sensor)
• Engine speed (crankshaft position sensor)
• Intake air temperature
• Manifold absolute pressure
• Pedal Position Sensor (1.6L has 2 sensors)
• Throttle position
The PCM adjusts ignition timing based on the fol-
lowing inputs.
• Coolant temperature
• Engine speed (crankshaft position sensor)
• Knock sensor
• Manifold absolute pressure
• Pedal Position Sensor (1.6L has 2 sensors)
• Throttle position
• Transmission
gear
switch)
• Intake air temperature
The PCM also adjusts engine idle speed through
the idle air control motor based on the following
inputs.
• Air conditioning sense
• Battery voltage
• Battery temperature
• Brake switch
• Coolant temperature
• Engine speed (crankshaft position sensor)
• Engine run time
• Manifold absolute pressure
• Pedal Position Sensor (1.6L has 2 sensors)
• Power steering pressure switch
• Throttle position
• Transmission
gear
switch)
• Vehicle distance (speed)
The Auto Shutdown (ASD) and fuel pump relays
are located in the Power Distribution Center (PDC).
The camshaft position sensor and crankshaft posi-
tion sensor signals are sent to the PCM. If the PCM
does not receive the signal within approximately 1
second of engine cranking, it deactivates the ASD
relay and fuel pump relay. When these relays are
deactivated, power is shut off from the fuel injectors,
ignition coils, oxygen sensor heating elements and
fuel pump.
The PCM contains a voltage converter that
changes battery voltage to a regulated 5 volts direct
current to power the camshaft position sensor, crank-
shaft position sensor, manifold absolute pressure sen-
sor, throttle position sensor, A/C pressure switch, A/C
pressure transducer, and vehicle speed sensor.
Powertrain Control Module Connectors
The PCM is an engine and transmission controller
module all in one, if the vehicle is equipped with an
automatic transmission. The PCM uses four wiring
selection (park/neutral
selection (park/neutral
ELECTRONIC CONTROL MODULES
harness connectors to receive and send engine and
transmission data. To ease assembly, the mating wir-
ing harness connector is color-coded. Each module con-
nector cavity has its own unique color identification
stripe located on the outside of each connector cavity.
The PCM module utilizes four wiring harness con-
nectors as described:
• Connector Cavity A is for Power & Ground
(Black)
• Connector Cavity B is for Engine Side (Orange)
• Connector Cavity C is for Headlamp & Dash
(White)
• Connector Cavity D is for Transmission (Green)
If equipped
NOTE: Connector Cavities A, B, C, And D must be
connected prior to battery connection and ignition
key on to avoid setting erroneous controller fault
codes. It is also recommended that cavity A con-
nector is made prior to any other connectors.
TRANSMISSION CONTROL
CLUTCH VOLUME INDEX (CVI)
An important function of the PCM is to monitor
Transmission Clutch Volume Index (CVI). CVIs rep-
resent the volume of fluid needed to compress a
clutch pack.
The PCM monitors gear ratio changes by monitor-
ing the Input and Output Speed Sensors. The Input,
or Turbine Speed Sensor sends an electrical signal to
the PCM that represents input shaft rpm. The Out-
put Speed Sensor provides the PCM with output
shaft speed information.
By comparing the two inputs, the PCM can deter-
mine transaxle gear ratio. This is important to the
CVI calculation because the PCM determines CVIs
by monitoring how long it takes for a gear change to
occur (Fig. 8).
Gear ratios can be determined by using the
DRBIII Scan Tool and reading the Input/Output
Speed Sensor values in the "Monitors" display. Gear
ratio can be obtained by dividing the Input Speed
Sensor value by the Output Speed Sensor value.
For example, if the input shaft is rotating at 1000
rpm and the output shaft is rotating at 500 rpm,
then the PCM can determine that the gear ratio is
2:1. In direct drive (3rd gear), the gear ratio changes
to 1:1. The gear ratio changes as clutches are applied
and released. By monitoring the length of time it
takes for the gear ratio to change following a shift
request, the PCM can determine the volume of fluid
used to apply or release a friction element.
The volume of transmission fluid needed to apply
the friction elements are continuously updated for
adaptive controls. As friction material wears, the vol-
ume of fluid need to apply the element increases.
8E - 7