OBJECTIVES

Automotive Fuel and Emissions Control Systems, 2/eBy James D. Halderman and Jim Linder

© 2009 Pearson Higher Education, Inc.Pearson Prentice Hall - Upper Saddle River, NJ 07458

OBJECTIVES

After studying Chapter 19, the reader will be able to:

1. Prepare for ASE Engine Performance (A8) certification test content area “E” (Computerized Engine Controls Diagnosis and Repair).

2. Discuss how crankshaft position sensors work.

3. List the methods that can be used to test CKP sensors.

4. Describe the symptoms of a failed CMP sensor.

5. List how the operation of the CKP sensor affects vehicle operation.



CRANKSHAFT AND CAMSHAFT POSITION SENSORS• Purpose and Function

– The crankshaft position sensor is primarily responsible for the following.

• Engine speed (RPM).

• Piston position for ignition timing control.

• Misfire detection.



CRANKSHAFT AND CAMSHAFT POSITION SENSORS

FIGURE 19-1 A typical magnetic crankshaft position sensor used on a General Motors V-6 engine.



CRANKSHAFT AND CAMSHAFT POSITION SENSORS

FIGURE 19-2 Some Hall-effect sensors look like magnetic sensors. This Hall-effect camshaft reference sensor and crankshaft position sensor have an electronic circuit built in that creates a 0- to 5-volt signal as shown at the bottom. These Hall-effect sensors have three wires: a power supply (8 volts) from the computer (controller); a signal (0 to 5 volts); and a signal ground.



MAGNETIC POSITION SENSORParts and Operation

• Some characteristics of a magnetic sensor include:– Two-wire sensors.– Sensors mounted near a gear or notched wheel. – Sensors where the faster the toothed wheel moves

past the sensor, the higher the frequency of the output signal.

– Magnetic position sensors generate a higher voltage signal with increased engine speed.



MAGNETIC POSITION SENSORParts and Operation

FIGURE 19-3 A magnetic sensor uses a permanent magnet surrounded by a coil of wire. The notches of the crankshaft (or camshaft) create a variable magnetic field strength around the coil. When a metallic section is close to the sensor, the magnetic field is stronger because metal is a better conductor of magnetic lines of force than air.



MAGNETIC POSITION SENSOR

• Testing Magnetic Position Sensors– Check the sensor connection and wiring. – Check that the sensor itself is magnetic. – Check the resistance of a magnetic sensor. – Scope testing a magnetic sensor.




FIGURE 19-4 A magnetic sensor being tested for magnetism. This sensor was able to hold a bolt and had about the same magnetic strength as a new sensor.




FIGURE 19-5 An AC voltage is produced by a magnetic sensor. Most sensors should produce at least 0.1 volt AC while the engine is cranking if the pickup wheel has many teeth. If the pickup wheel has only a few teeth, you may need to switch the meter to read DC volts and watch the display for a jump in voltage as the teeth pass the magnetic sensor. (Courtesy of Fluke Corporation)




FIGURE 19-6 A magnetic sensor connected to a digital storage oscilloscope.




FIGURE 19-7 (a) Magnetic sensor waveform as shown on a digital storage oscilloscope. (b) A sync notch provides a signal to the computer that cylinder number one is at top dead center (TDC). (Courtesy of Fluke Corporation)



HALL-EFFECT DIGITAL SENSORS

• Parts and Operation– The typical Hall-effect sensor has three wires:

• Power (can be 8 to 12 volts)

• Ground

• Signal

• Testing Hall-Effect Sensors– If the scope pattern indicates a problem or a scope is not

available, other tests include:• Check the sensor connection and wiring.

• Check the sensor damage.




FIGURE 19-8 (a) The connection required to test a Hall-effect sensor. (b) A typical waveform from a Hall-effect sensor. (Courtesy of Fluke Corporation)




FIGURE 19-9 The waveform from a Hall-effect sensor (switch) should be checked for consistency and sharp transitions. (Courtesy of Fluke Corporation)



MAGNETIC-RESISTIVE SENSORS

• Parts and Operation– A magnetic-resistive sensor (abbreviated MRE) is similar

to a magnetic sensor but, instead of producing an analog voltage signal, the electronics inside the sensor itself generate a digital on/off signal or an output.

• Testing a Magnetic-Resistive Sensor– If the scope pattern indicates a problem or a scope is not


• Check that the sensor itself is magnetic.



MAGNETIC-RESISTIVE SENSORS

FIGURE 19-10 The input signals to a magnetic resistive sensor and the electronic circuits inside the sensor convert them to a digital (on and off) signal.



OPTICAL SENSORS

• Parts and Operation– Optical sensors typically use a photo diode and/or a photo

transistor and a slotted disk to detect distributor position. – The output is a digital on/off (square wave) signal that is

very accurate.

• Testing Optical Sensors– If the scope pattern indicates a problem or a scope is not


• Check the sensor or wiring for damage.



OPTICAL SENSORS

FIGURE 19-11 (a) The low-resolution signal has the same number of pulses as the engine has cylinders. (b) A dual trace pattern showing both the low-resolution signal and the high-resolution signals that usually represent 1 degree of rotation. (Courtesy of Fluke Corporation)



PCM USES OF THE CRANKSHAFT AND CAMSHAFT POSITION SENSOR• The crankshaft and camshaft position sensors are used by

the powertrain control module for many functions including the following.– The crankshaft position is normally used to determine engine speed

(RPM). – Camshaft position sensor information is usually used to determine

the cylinder position for fuel control (when to trigger the injectors). – Engine speed input is used to calculate IAC counts to maintain the

target idle speed.– Crankshaft position sensors are used primarily as the spark timing

input sensor. – The crankshaft position sensor is used as an input for traction

control.



PCM USES OF THE CRANKSHAFT AND CAMSHAFT POSITION SENSOR

FIGURE 19-12 A General Motors camshaft sensor (CMP) pattern as shown on a digital storage oscilloscope. The camshaft sensor is used by the computer to help determine the engine crankshaft speed (OBD II) and camshaft position. Besides ignition timing and misfire input information, the camshaft sensor signal is also used for fuel-injection pulses. This signal uses different pulse widths to signal the computer the exact position of the distributor. (Courtesy of Fluke Corporation)



PCM USES OF THE CRANKSHAFT AND CAMSHAFT POSITION SENSOR• Re-Synchronizing the Crankshaft Position

Sensor– Whenever the PCM or the crankshaft position sensor are

replaced, the new part must be “learned” or synchronized before the engine will operate correctly.

– Most scan tools are capable of performing the re-learn process, which often calls for accelerating the engine for the new parameters to be learned.



PCM USES OF THE CRANKSHAFT AND CAMSHAFT POSITION SENSOR



SUMMARY

1. The crankshaft position (CKP) sensor is used as an input sensor to the PCM for engine speed (RPM) and piston position for spark timing control.

2. A camshaft position sensor is also called a cylinder identification (CID) sensor and is primarily used to time the sequential fuel injection.

3. A magnetic position sensor generates an analog voltage signal.

4. A Hall-effect position sensor generates a digital (on and off) voltage signal.

5. A magnetic-resistive position sensor creates a digital output signal.

6. An optical position sensor creates a digital output signal.



REVIEW QUESTIONS

1. What is the primary purpose for a crankshaft position (CKP) sensor?

2. What is the primary purpose for a camshaft position (CMP) sensor?

3. How does a magnetic sensor work, and how is it tested?

4. How does a Hall-effect sensor work, and how is it tested?

5. How does a magnetic-resistive sensor work, and how is it tested?

6. How does an optical sensor work, and how is it tested?



CHAPTER QUIZ

1. A magnetic position sensor is being tested with an ohmmeter. The display reads 102 KΩ. Technician A says that the sensor resistance is within the normal range. Technician B says that the coil winding inside the sensor is shorted. Which technician is correct?a) Technician A only

b) Technician B only

c) Both Technicians A and B

d) Neither Technician A nor B



CHAPTER QUIZ

1. A magnetic position sensor is being tested with an ohmmeter. The display reads 102 KΩ. Technician A says that the sensor resistance is within the normal range. Technician B says that the coil winding inside the sensor is shorted. Which technician is correct?a) Technician A only






CHAPTER QUIZ

2. Technician A says that the crankshaft position (CKP) sensor is used by the PCM to determine engine speed (RPM). Technician B says that the camshaft position (CMP) is used by the PCM to determine the timing of the fuel injectors. Which technician is correct?a) Technician A only






CHAPTER QUIZ

2. Technician A says that the crankshaft position (CKP) sensor is used by the PCM to determine engine speed (RPM). Technician B says that the camshaft position (CMP) is used by the PCM to determine the timing of the fuel injectors. Which technician is correct?a) Technician A only






CHAPTER QUIZ

3. Which sensor produces an analog (varying voltage) output signal?a) Magnetic

b) Hall-effect

c) Optical

d) Magnetic-resistive



CHAPTER QUIZ

3. Which sensor produces an analog (varying voltage) output signal?a) Magnetic

b) Hall-effect

c) Optical




CHAPTER QUIZ

4. Which type of sensor is most likely to be used to sense each degree of rotation of the crankshaft?a) Magnetic

b) Hall-effect

c) Optical




CHAPTER QUIZ

4. Which type of sensor is most likely to be used to sense each degree of rotation of the crankshaft?a) Magnetic

b) Hall-effect

c) Optical




CHAPTER QUIZ

5. A magnetic sensor usually has how many wires?a) 1

b) 2

c) 3

d) 4



CHAPTER QUIZ

5. A magnetic sensor usually has how many wires?a) 1

b) 2

c) 3

d) 4



CHAPTER QUIZ

6. A Hall-effect sensor usually has how many wires?a) 1

b) 2

c) 3

d) 4



CHAPTER QUIZ

6. A Hall-effect sensor usually has how many wires?a) 1

b) 2

c) 3

d) 4



CHAPTER QUIZ

7. In Figure 19-13, the top waveform is produced by what type of sensor?

a) Magnetic

b) Hall-effect

c) Either a or b

d) Neither a nor b

FIGURE 19-13 Typical crankshaft position sensor waveforms.



CHAPTER QUIZ

7. In Figure 19-13, the top waveform is produced by what type of sensor?

a) Magnetic

b) Hall-effect

c) Either a or b

d) Neither a nor b




CHAPTER QUIZ

8. In Figure 19-13, the bottom waveform is produced by what type of sensor?

a) Magnetic

b) Hall-effect

c) Either a or b

d) Neither a nor b




CHAPTER QUIZ

8. In Figure 19-13, the bottom waveform is produced by what type of sensor?

a) Magnetic

b) Hall-effect

c) Either a or b

d) Neither a nor b




CHAPTER QUIZ

9. Extending engine cranking before starting is a symptom of a defective _____ sensor.a) Crankshaft position (CKP)

b) Camshaft position (CMP)

c) Both CKP and CMP

d) Neither CKP nor CMP



CHAPTER QUIZ

9. Extending engine cranking before starting is a symptom of a defective _____ sensor.a) Crankshaft position (CKP)

b) Camshaft position (CMP)

c) Both CKP and CMP

d) Neither CKP nor CMP



CHAPTER QUIZ

10.A P0337 DTC is being discussed. Technician A says that a broken CKP reluctor wheel could be the cause. Technician B says that a defective CKP could be the cause. Which technician is correct?a) Technician A only






CHAPTER QUIZ

10.A P0337 DTC is being discussed. Technician A says that a broken CKP reluctor wheel could be the cause. Technician B says that a defective CKP could be the cause. Which technician is correct?a) Technician A only




OBJECTIVES

Documents

magnetic sensors

pearson higher education

crankshaft position

magnetic position sensorparts

emissions control systems

halleffect sensors

eby james

jim linder