110 Engine Speed Sensor Signal - Open Circuit
P0336
110 Engine Speed Sensor Signal - Open Circuit
Function
A soft iron core partially bundles the magnetic field produced by the permanent magnet which then enters the space and closes again through the magnetically conductive parts of the engine. A steel toothed ring moving past the face of the sensor affects the magnetic field. The change in the magnetic field induces an electric charge in the coil winding which is used by the DME control module.
Engine speed and crankshaft position
The piston position of a cylinder is used as a measuring variable to determine the ignition timing. The pistons of all the cylinders are connected to the crankshaft by connecting rods. A sensor on the crankshaft therefore supplies information about the piston position of all the cylinders.
The speed at which the crankshaft position changes is therefore known as the engine speed, expressed as the number of revolutions of the crankshaft per minute (rpm). This important input variable is also calculated from the signal of the crankshaft position.
Diagnosis conditions
- Engine running
P0336:
Signal generation
A ferromagnetic sensor wheel with space for 60 teeth, with two teeth left out (gear notch) is mounted on the crankshaft. The speed sensor scans the tooth sequence of 58 teeth. When the sensor wheel teeth now pass the sensor, they alter the magnetic flux in the latter.
The amplitude of the alternating voltage diminishes as the gap between the sensor and the sensor wheel grows, and rises sharply as the speed increases.
Wiring Diagram
NOTE: The distance of the sensor is not adjustable.
The steel toothed ring is stamped from sheet steel. Take great care when installing and removing the flywheel, because force acting on the steel toothed ring can deform it, leading to a defective signal.
Diagnosis Procedure
Part 1:
Part 2:
1 Check signal with engine tester.
1. Connect special tool 9637.
2. Connect engine tester. Using special input, connect positive cable to pin III/32, negative cable to pin III/46.
3. Start engine or crank engine with starter motor.
The display pictured opposite should appear on the oscilloscope:
2 Check wiring from rpm/crankshaft position sensor to DME control module for open circuit and short circuit.
1. Connect special tool 9637 to wiring harness.
2. Remove connector of rpm/crankshaft position sensor.
3. Connect ohmmeter to special tool 9637, pin III/32, and connector, pin 1.
Display: 0 - 5 ohms
4. Connect ohmmeter to special tool 9637, pin III/46, and connector, pin 2.
Display: 0 - 5 ohms
5. Connect ohmmeter to special tool 9637, pin III/45, and connector, pin 3.
Display: 0 - 5 ohms
6. Connect ohmmeter to special tool 9637, pin III/32, and ground.
Display: infinity ohms
7. Connect ohmmeter to special tool 9637, pin III/46, and ground.
Display: infinity ohms
3 Perform adaptation.
1. Switch on the ignition.
2. Wait one minute. Do not press the accelerator.
3. Switch off the ignition for at least 10 seconds.
4. Read out the fault memory.