Operation; Camshaft Position Sensor Description - Chrysler PT Cruiser Service & Repair Manual

8I - 4 IGNITION CONTROL
AUTO SHUT DOWN RELAY (Continued)
When energized, the ASD relay on SBEC vehicles
supplies battery voltage to the fuel injectors, ignition
coils and the heating element in each oxygen sensor.
When energized, the ASD relay on NGC vehicles
provides power to operate the injectors, ignition coil,
generator field, O2 sensor heaters (both upstream
and downstream), evaporative purge solenoid, EGR
solenoid (if equipped)
equipped), and NVLD solenoid (if equipped).
For both SBEC and NGC vehicles, the ASD relay
also provides a sense circuit to the PCM for diagnos-
tic purposes. If the PCM does not receive 12 volts
from this input after grounding the control side of
the ASD relay, it sets a Diagnostic Trouble Code
(DTC). The PCM energizes the ASD any time there is
an engine speed that exceeds a predetermined value
(typically about 50 rpm). The ASD relay can also be
energized after the engine has been turned off to per-
form an O2 sensor heater test, if vehicle is equipped
with OBD II diagnostics.
As mentioned earlier, the PCM energizes the ASD
relay during an O2 sensor heater test. This test is
performed only after the engine has been shut off for
SBEC vehicles. On NGC vehicles it checks the O2
heater upon vehicle start. The PCM still operates
internally to perform several checks, including moni-
toring the O2 sensor heaters.
CAMSHAFT POSITION
SENSOR
DESCRIPTION
On 2.0/2.4L engines the camshaft position sensor is
mounted to the rear of the cylinder head (Fig. 1),
(Fig. 2),. On 1.6L engines it is mounted on the front
side of the cylinder head.

OPERATION

The PCM sends approximately 5 volts to the Hall-
effect sensor. This voltage is required to operate the
Hall-effect chip and the electronics inside the sensor.
The input to the PCM occurs on a 5 volt output ref-
erence circuit. A ground for the sensor is provided
through the sensor return circuit. The PCM identifies
camshaft position by registering the change from 5 to
0 volts, as signaled from the Camshaft Position sen-
sor (Fig. 3).
On 2.0/2.4L engines a target magnet attaches to
the rear of the camshaft and indexes to the correct
position. The target magnet has fourteen different
poles arranged in an asymmetrical pattern. As the
target magnet rotates, the camshaft position sensor
senses the change in polarity (Fig. 5) and (Fig. 4).
The PCM determines fuel injection synchronization
and cylinder identification from inputs provided by
wastegate solenoid (if
Fig. 1 Camshaft Position Sensor -2.0/2.4L DOHC
1 - PCV VALVE
2 - EGR VALVE
3 - CAMSHAFT POSITION SENSOR
Fig. 2 CAMSHAFT POSITION SENSOR - 2.4L TURBO
the camshaft position sensor (Fig. 1) and crankshaft
position sensor. From the two inputs, the PCM deter-
mines crankshaft position.
The sensor input switches from high (5 volts) to
low (0.30 volts) as the target magnet rotates. When
the north pole of the target magnet passes under the
sensor, the output switches high. The sensor output
switches low when the south pole of the target mag-
net passes underneath.
On 1.6L a raised platform on the cam sprocket
serves as a target. When the sensor detects the step,
the input voltage from the sensor to the PCM
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