Lotus Elise Service Notes page 251

Lotus Service Notes
Section EMN
EMN.7 - CRANKSHAFT POSITION SENSOR
The signals provided by the crankshaft position sensor enable the ECM to determine:
engine speed;
crankshaft position.
The inductive type sensor is mounted by a single fixing into a flange at the right hand rear of the cylinder
block, where it protrudes towards reluctor ring machined into the front face of the flywheel.
The reluctor ring has raised poles at 10° intervals which pass within an air gap of the sensor tip, and
provide a voltage pulsing reference signal used for engine speed calculation. Four missing poles enable the
ECM to determine the crankshaft position in order to correctly time the ignition and fuel injection sequence.
Missing poles are positioned as follows, relative to no.1 cylinder:
Standard
TDC;
50° BTDC;
180° BTDC;
240° BTDC.
WC
110° BTDC;
150° BTDC;
300° BTDC;
330° BTDC.
Note that on standard engines using grouped injection (1 with 4; 2 with 3), it is not necessary to determine
which cylinders are on the firing, and which on the exhaust stroke. On the W C engine, using fully sequential
injection, an additional signal from the camshaft position sensor is required to determine the correct injection
and ignition sequence.
To prevent damage from engine overspeed on acceleration, the ECM will implement fuel cut-off at en-
gine speeds above approximately 7,000 rpm by inhibiting the earth path for the injectors. Fuel is progressively
reinstated as engine speed falls.
Faults in the crankshaft sensor or circuit may be indicated on the scanner tool by a '0' display during
cranking. On standard engines, sensor pin no.1 connects to ECM terminal 32 and sensor pin 2 to ECM
terminal 31. Sensor resistance is 1.3 kohms. Fixing screw torque = 6 Nm.
Page 10
2GQQ / Q t