Chrysler Sebring 2005 Service Manual page 1357

14 - 22 FUEL INJECTION
CRANKSHAFT POSITION SENSOR (Continued)
OPERATION
The Crankshaft Position (CKP) sensor is a Hall-ef-
fect sensor. The PCM sends approximately 8 volts to
the Hall-effect sensor for the SBEC vehicles and 5
volts for the NGC vehicles. This voltage is required
to operate the Hall-effect chip and the electronics
inside the sensor. A ground for the sensor is provided
through the sensor return circuit of the PCM. The
input to the PCM occurs on a 5 volt output reference
circuit.
The notches generate pulses from high to low in
the crankshaft position sensor output voltage (Fig. 6).
When a metal portion of the counterweight aligns
with the crankshaft position sensor, the sensor out-
put voltage goes low (less than 0.5 volts). When a
notch aligns with the sensor, voltage goes high (5.0
volts). As a group of notches pass under the sensor,
the output voltage switches from low (metal) to high
(notch) then back to low.
If available, an oscilloscope can display the square
wave patterns of each voltage pulses. From the width
of the output voltage pulses, the PCM calculates
engine speed. The width of the pulses represent the
amount of time the output voltage stays high before
switching back to low. The period of time the sensor
output voltage stays high before switching back to
low is referred to as pulse width. The faster the
engine is operating, the smaller the pulse width on
the oscilloscope.
1 - MACHINED NOTCHES
Fig. 6 Timing Reference Notches - 4 Cylinder
For SBEC vehicles, each group of timing reference
notches, the first notch represents 69 degrees before
top dead center (BTDC). The second notch represents
49 degrees BTDC. The third notch represents 29
degrees. The last notch in each set represents 9
degrees before top dead center (TDC). There is also a
notch at 11 degrees before top dead center (TDC).
The crankshaft position sensor detects slots cut
into the transmission driveplate extension (Fig. 7).
There are 3 sets of slots. Two sets contains 4 slots,
and 1 set contains 5 slots for a total of 13 slots (Fig.
8). Basic timing is set by the position of the last slot
in each group. Once the Powertrain Control Module
(PCM) senses the last slot, it determines crankshaft
position (which piston will next be at TDC) from the
camshaft position sensor input. The 4 pulses gener-
ated by the crankshaft position sensor represent the
69°, 49°, 29°, and 9° BTDC marks. It may take the
PCM one engine revolution to determine crankshaft
position.
The PCM uses crankshaft position reference to
determine injector sequence, ignition timing and the
presence of misfire. Once the PCM determines crank-
shaft position, it begins energizing the injectors in
sequence.
2 - CRANKSHAFT POSITION SENSOR
JR