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CAMSHA FT & CRANKSHA FT SENSORS KNOW HOW Cam and Crankshaft sensors (also known as Engine Speed & Position Sensors) are a vital part of the engine management system so it’s handy to know your way around them. That’s why we’ve put together this simple driveby guide to give you the knowhow CAMSHA FT & you need. Camshaft sensor CRANKSHA FT ......

Crankshaft sensor SENSORS? ...... WE’VE GOT YOUR BACK! Sensor; a device which detects or measures a physical property and records, indicates, or otherwise responds to it. WHAT DO THEY DO? The sensors, of which there are two types,

Cam and Crankshaft, provide information Camshaft about engine speed and the exact position of several engine parts, crankshaft/pistons and camshaft/valves.

Supplying this information to the engine control unit (ECU) enables the fuel injection and ignition systems to function efficiently. Valves

Piston

Crankshaft CRANKSHA FT SENSOR TIMELINE DIFFERENT Used for petrol and diesel engines with electronic injection systems DESIGNS OF Petrol: starting in the 80s (‘Motronic’ 1979); from 1990 almost all cars have crank sensors CRANKSHA FT Diesel: starting with ‘common rail’ technology, 1997 (Alfa 156 JTD) SENSORS

re u s s re P te lu 2 o s 0 b 0 A w lo 0 ld F o if ir n A a s s M a = M F = 1 DIESEL ENGINES A F 9 M A 9 M 0

PETROL ENGINES 19 80

19 70 A selection of common sensor designs INSTALLATION POSITION CRANKSHA FT SENSOR The crankshaft is connected via rods to the pistons and Crankshaft speed: via flywheel and clutch to the gearbox. It converts The frequency of rotation or rotational the linear up and down speed of the crankshaft is called ‘crankshaft movements of the pistons speed’ or for most practical purpose ‘engine to a rotary motion. speed’ which is often displayed on the dashboard display as RPM - Revolutions per minute.

The sensor must be positioned so that it can easily detect the rotational measurement of the shaft INSTALLATION POSITION CRANKSHA FT SENSOR (CONTINUED)

The crankshaft sensor is installed near the TASK OF THE crankshaft, in or near the lower engine block It picks up the signal of a toothed wheel or disk CRANKSHA FT which rotates with the crankshaft. SENSOR The crankshaft sensor measures the rotational speed and angular position of the crankshaft. This is the most important information the engine control sensor unit (ECU) needs to be able to work.

Toothed wheel connected to crankshaft This information is used to inject fuel and trigger the ignition system etc.

The sensor can be positioned either end (drive belt or flywheel end) of the crankshaft or in the middle. In some cases the sensor is in contact with oil. u u

Crankshaft Sensor ECU RPM Counter

Flywheel end installation position Engine Block middle installation Drive Belt end installation position position (sensor removed) Hall effect sensor n Integrated electronics n External power supply 5V n Square output signal (0V/5V) n Can detect a position even if toothed wheel is at standstill (tooth or gap) n 3 Pins

HOW DOES A Square output signal CRANKSHA FT SENSOR Inductive Sensor n Generates a signal, no external power supply WORK? n Wave-form output signal Crankshaft sensors generally use either the Hall effect or n Only generates a signal when inductive principle. toothed wheel turns n They cannot be interchanged. Voltage rises with toothed wheel ! speed, and depends on distance to toothed wheel n 2 or 3 Pins (3rd pin is shielding ground connection)

Wave output signal CRANKSHA FT SPEED HALL & POSITION EFFECT DETECTION SENSOR Function Principles The crankshaft sensor can provide the ECU with data relating to VS. crankshaft speed and relative rotational position. The toothed wheel has one bigger gap, at a dedicated position. INDUCTIVE The signal generated by the sensor reflects this big gap, and so the ECU can calculate the angular position. SENSOR That is why the sensors can be called: n Engine speed sensor Key benefits of Hall effect n Crankshaft speed sensor sensors n Crankshaft position sensor n Speed detection from standstill Sensor (low speed detection) These are often the same part!! Toothed wheel with bigger gap n The design of the sensor is smaller and lighter Speed = amount of teeth n The sensitivity to electromagnetic Position = bigger gap per second interference is lower n Changes in the air gap between the sensor and the toothed wheel have no direct effect on the signal n Higher resistance to vibrations and temperature fluctuations Square output signal THE EFFECTS OF CRANKSHA FT Diagnostic information The engine will not run/start if the sensor has completely SENSOR failed. In most cases a DTC (diagnostic trouble code) PO335 will be stored. FAILURE Symptoms: The sensor delivers the input signal for the ECU n Bad starting (see below) n Engine stalls / dies off Without that signal, the ECU cannot keep the engine running n Bad performance ! > Sensor failure = Car breakdown n Misfiring Bad starting: Output voltage generated by the sensor depends on: n Toothed rotor speed (especially inductive types) n Distance from sensor to toothed rotor n Amount of functioning windings in the sensor This may lead to the following effect: If gap is too big or the sensor is weak the engine may run at idle speed and above. However, the engine may be difficult to start, may not start using the starter motor but might start if towed.

! Reasons for failure Sensors have no dedicated replacement interval! Typical reasons for failures are: Water in the connector or sensor Broken wires Age

CAMSHA FT SENSORS The camshaft which is driven by the crankshaft via a timing belt, chain or gears rotates at half the speed of the crankshaft and open and closes the valves. The camshaft sensor measures the relative rotational position of the camshaft.

INSTALLATION POSITION CAMSHA FT SENSOR Engine with two camshafts “DOHC”

Camshaft position: The position of the camshaft is (together with the crankshaft position) used to determine the piston's position within the cylinder and which part of the combustion cycle it is on e.g. intake, compression, power or exhaust.

Camshaft sensor u

The sensor must be located so it can easily detect the rotational movement of the camshaft INSTALLATION TASK POSITION OF THE CAMSHA FT CAMSHA FT SENSOR SENSOR

The camshaft sensor measures the position of the camshaft. This signal - in u conjunction with the crankshaft position - is used to determine in which stroke each cylinder is on. The ECU needs the signal to determine when to inject fuel and to trigger the spark plug.

Camshaft Sensor The camshaft sensor(s) Fuel injector is installed near the camshaft(s), in or near

the cylinder head.

Camshaft position u u u

ECU Camshaft Sensor u

Ignition APPLICATION CAMSHA FT SENSORS DIFFERENT Used for petrol and diesel engines with electronic injection systems. Many newer engines have two camshafts, and often (not always) DESIGNS OF two camshaft sensors. With variable camshaft timing, the sensor(s) may also be used to CAMSHA FT monitor this function. SENSORS

Variable camshaft timing

A selection of common sensor designs Two camshafts (DOHC)

Hall effect sensor

n Integrated electronics

H OW DOES A n External power supply 5V n Square output signal (0V/5V)

CAMSHA FT n Can detect a position even if toothed wheel is at standstill SENSOR n 3 Pins WORK? Camshaft sensors generally use the Hall effect principle.

Square output signal

THE EFFECTS OF CAMSHA FT SENSOR FAILURE DIAGNOSTIC Failure mains no input signal for the ECU INFORMATION However, without that signal, the ECU can (in most cars) keep the engine running Sensor failure = Delayed starting, MIL on, DTC P0340 CAMSHA FT AND ! If engine has variable camshaft timing, this function will not work with a defective camshaft sensor CRANKSHA FT SENSORS If DTC for Cam and Crankshaft sensors is displayed it is possible that there is a problem with engine timing (timing belt, timing chain). DTC will hint at ‘synchronization’. Typical codes for variable camshaft timing problems are: P0011 and P0021 (Camshaft position sensor ‘Bank 1’ and Camshaft position sensor “Bank 2”). Check: ! Reasons for failure 4 Sensors have no dedicated replacement interval! Oil control valve Typical reasons for failures are: Water in the connector or sensor 4 Oil control valve filter screen Broken wires 4 Camshaft timing/gears Age 4 The electrical side of the actuation 4 The ECU DIAGNOSTIC INFORMATION CAMSHA FT AND CRANKSHA FT SENSORS After replacing a sensor: Many cars require a ‘learning’ procedure. A scan tool may be required, sometimes a vehicle model specific special procedure with brake and accelerator pedal is required as well. The position of the sensor ‘elements’ may differ very slightly in the replacement sensor. The ECU will 'learn' the new position after several drive cycles.

Sensor element position Sensor element position before replacing after replacing facebook.com/ngksparkplugsuk

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