LT & LS Ignition Parts and Accessories

How Does LS Ignition System Work?

Starting at the spark plugs, LS engine coil packs are connected with spark plug wires. The coils are usually mounted to the valve covers, but can be relocated with longer wires. The coil packs are connected to the engine computer / PCM with a wiring harness. The engine computer receives information from a reluctor wheel / ring which either has 24 or 58 teeth, depending on the year (around 2006-2007 GM went from a 24X to 58X ring) as well as other input sensors and adjusts timing appropriately for driving conditions.

How To Test Chevy LS Ignition

Assuming the spark plugs are working properly and not oil or fuel fouled, the first way to test the ignition system is with an ignition tester. This type of tester allows the spark plug to stay in the engine. It works by removing the spark plug wire from the spark plug and connecting it to the tester.

With the help of another person, the engine is turned over while watching the tester to see if there is a spark. If there is a spark, check each of the other ignition coils to confirm all coils are functioning. If there is not a spark, the next step is checking the spark plug wire and ignition coil.

Remove the spark plug wire and attach the ignition tester directly to the ignition coil. Follow the same procedure to determine if there is a change. If there is now spark when there wasn't at the wire, the spark plug wire needs to be replaced. However, if there is no spark with both the spark plug and wire removed from the system test, the ignition coil is next to check.

Unplug the ignition coil wiring harness connector. Using a multimeter, adjust the setting to read "volts" and locate the pin for the 12 volt circuit that provides power to the coil and attach the positive lead from the multimeter to it. The negative lead from the multimeter goes to the negative terminal on the battery. With the help of a friend, turn the ignition key to the "ON" position (do not crank). The multimeter should read between 10 to 12 volts. If it reads the correct voltage, the coil is receiving power and additional wires need to be checked. If it doesn't receive 12 volts, an issue lies with the wiring harness or source of the power circuit for the coils.

To check the chassis ground wire for the coil, locate the proper connector on the coil harness and contact it to the black multimeter probe. Next, connect the red multimeter probe to the positive battery terminal. Then have a friend turn the key to the "ON" position (do not crank). The multimeter should read 12 volts. If it does, the ground is good. If it doesn't, the chassis ground circuit is bad.

The next test is with the ground provided by the PCM. This is done identically to the chassis ground but switching the pin on the coil harness to the PCM ground. If 10-12 volts is observed the PCM ground circuit is good, otherwise, it is bad.

To check the triggering signal to the coil the multimeter is switched to the Hertz (Hz) function. The black probe from the multimeter is contacted / touched to the PCM ground pin. The red probe goes to the positive terminal on the battery. With a helper cranking and starting the engine, the multimeter should show varying readings between 5 to 8 hertz. If it is not, there is an issue with the triggering circuit.

If there is no spark, and each wire in the ignition coil wiring harness is confirmed working, the ignition coil is bad and needs to be replaced.

If any of the wires fails a test, the wiring harness needs to be tested with the multimeter in the continuity setting to find a break or bad connector.

If the wiring harness is confirmed to be functioning ok, the PCM is the last option (though rare) on being faulty and requiring replacement.

How To Wire Ignition Coil LS

Ignition coils for LS engines have different wiring depending on which ignition type you are using (for example, LS1, LS2, LS3, LS6, etc.). In most LS applications, the wiring includes pins for a PCM signal and signal ground wire as well as a switch 12v power wire and a chassis ground wire. To get the correct wiring for your ignition coil, refer to your specific repair or shop manual.

Can't Find The LT Or LS Performance Ignition Parts You Are Looking For?

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