Define these Technical Terms using the textbook:
1. analog scope pattern
2. digital scope pattern
3. digital thermometer
4. ignition load test
5. oscilloscope
6. reference voltage test
7. snapshot
8. scan tool data stream values
Answer these discussion questions using the textbook:
1. What is electromagnetic interference (EMI)?
Read the chapter summary below:
■ Strategy-based diagnostics involves using a consistent, logical procedure to narrow down possible problem sources.
■ Scan tool data stream values are “live” electrical values measured with the vehicle running or driving.
■ A breakout box allows you to pinpoint test electrical values at specific pins on the ECM or in the computer system.
■ Electromagnetic interference results from induced voltage into wires and can cause a computer to malfunction.
■ Scope voltage is shown on the scope screen along the vertical (up-and-down) axis or scale.
■ Scope time is given on the scope screen on the horizontal scale in degrees, milliseconds, or duty cycle.
■ A primary scope pattern shows the low voltage or primary voltage changes in an ignition system.
■ The secondary scope pattern shows the actual high voltages needed to fire the spark plugs.
■ The term superimposed means that all the cylinder wave forms are placed one on top of the other.
■ The parade pattern, also called the display pattern, lines up the wave form for each cylinder end-to-end across the screen.
■ In a raster pattern, or stacked pattern, voltage wave forms are arranged individually one above the other, starting with the number one cylinder on the bottom of the screen.
■ Some electrical connectors are sealed and do not allow easy probing. You may need to install a test connector or jumper wires between the two halves of the connector to probe sensor voltages.
■ An oscilloscope can be used to check the ac and dc voltages leaving an electronic control module or ECM.
■ A flight record test stores the sensor wave form in the scope memory when a problem occurs.