ASE P2 Test Preparation Guide: Ignition System

ASE P2 Test Preparation Guide: Ignition System

ASE P2 Test Preparation Guide: Ignition System

Sample Review Questions:
1. Which of the following components generates a timing trigger signal for the ignition system?
a. Crankshaft position sensor
b. Ignition module
c. Ignition coil
d. Rotor

2. Counterman A says a Coil-On-Plug (COP) ignition system has one ignition coil for every pair of spark plugs. Counterman B says a “Waste Spark” ignition system does not use a distributor, rotor or spark plug wires.  Who is right?
a. Counterman A only
b. Counterman B only
c. Both Counterman A and B
d. Neither one

3. A spark plug’s “heat range” can be determined by:
a. Its part number
b. Measuring the length of the spark plug
c. Measuring the diameter of the spark plug
d. Measuring the electrode gap

4. All of the following about iridium spark plugs is true EXCEPT:
a. The electrode gap is different than an ordinary spark plug
b. They usually have a single ground electrode
c. They typically have a smaller diameter center electrode than ordinary spark plugs
d. They have a service life of 100,000 miles or more

1A, 2D, 3A, 4A

1. The Crankshaft Position Sensor (CKP) may be mounted on the front, side or rear of the engine. The sensor reads notches in the crankshaft balancer, crankshaft or flywheel to generate a timing signal for the PCM and ignition system. There are two basic types of crank sensors: magnetic and Hall effect. Loss of the sensor signal will prevent the engine from starting (no spark). In older engines with distributors, a magnetic or Hall effect pickup in the distributor generates a trigger signal for the ignition module to fire the ignition coil. A bad pickup or damaged wiring can cause a no spark condition.

2. Coil-on-plug ignition systems have one coil per spark plug, mounted directly over the spark plugs. No spark plug wires are used.

Some distributorless ignition systems (DIS) are “waste spark” systems, meaning one coil fires two spark plugs simultaneously. The shared plugs are opposite each other in the engine’s firing order, so the second plug fires during the exhaust stroke and does nothing. The advantage with the waste spark approach is that it reduces the number of individual coils in the ignition system by half. The disadvantage is the waste spark accelerates electrode wear in the spark plugs unless double platinum or iridium spark plugs are used.

3. The “heat range” (operating temperature) of a spark plug depends on the internal design of the center electrode, the distance heat has to travel inside the plug from the electrode to the metal shell and the conductivity of the center electrode. Copper core center electrodes are often used to increase thermal conductivity and provide a broader heat range.

If a spark plug is too cold for an engine application, it may experience fouling and misfiring problems. If a spark plug is too hot for an engine application, it may become a source of pre-ignition/detonation when the engine is under load.

The heat range is determined by the spark plug manufacturer with engine testing, and is encoded in the spark plug number. You can use a heat range reference chart to look up hotter or colder spark plugs within a brand line, or use a cross-reference chart to look up other brand spark plugs with a similar heat range.

4. Iridium spark plugs have a thin wire iridium center electrode. Like platinum plugs, they typically have a service life of 100,000 miles plus. Most iridium plugs have a single ground electrode, and the gap is set the same as a standard spark plug. Some platinum plugs have two or four ground electrodes and have a wide, nonadjustable surface gap design.


Sections covered:

Automatic Transmission



Cooling System



Engine Mechanical Parts


Fuel System



Ignition System

Manual Transmission

Suspension and Steering



You May Also Like

Common Causes of Oil Leaks

Generally speaking, there are only a few common causes for the majority of oil leaks on the road.

Pick a parking lot, any parking lot, and you can tell what spaces get used the most by the number of oil spots. It’s easy to think of it as just a mess, but the unfortunate reality is it’s a bigger cause of pollution than meets the eye.

Turbochargers and GDI: A Winning Combination

Automakers have turned to turbochargers and GDI to boost fuel economy and horsepower – with less displacement.

Decoding Honda’s VINs

The automaker’s engineering prowess isn’t necessarily on display in its VIN encoding.

Staying Comfortable Behind the Counter

Ergonomics can play a big role in your on-the-job comfort and overall health.

Auto Parts Manufacturers Share Their Perspectives

Chloe Hung, Eric Luftig, Michael Kitching, Eric Sills and Matt Roney discuss what’s top of mind for their businesses.

Other Posts

A Closer Look at Crankshafts

With the great power of the engine comes the great responsibility of the crankshaft.

Spring Cleaning and Seasonal Stocking

Before the public comes calling for their spring cleanup needs, this is the perfect time to take care of our own.

Ball Joints: How Much Play Is Too Much?

There’s a common misconception that any play in a ball joint means it’s
wearing out.

Selling Tools for Underhood Repairs

The category is spread across several vehicle systems, and includes a number of specialty tools.