When the ignition control module fails, your 2.8 liter Chevy S10 (GMC S15) will crank but not start. Testing the GM 7 pin ignition control module is easier than you think and you don't even have to remove it (from the vehicle) to test it.
Also, you don't need any expensive or fancy diagnostic testing equipment. With a few simple/basic tools and a very simple process of elimination you'll be able to correctly conclude that the ignition control module is fried or not. In this tutorial I will show you how to test it then a step-by-step manner.
Contents of this tutorial at a glance:
- Symptoms Of A Bad Ignition Control Module.
- What Tools Do I Need To Test The ICM?
- Ignition Control Module Circuits.
- TEST 1: Making Sure The ICM Is Getting Power.
- TEST 2: Verifying The Ignition Coil Activation Signal.
- TEST 3: Verifying The Pick-Up Coil's Signal.
- Where To Buy The Ignition Control Module And Save.
- More GM 2.8L Tutorials.
Puedes encontrar este tutorial en Español aquí: Cómo Probar El Módulo De Encendio (2.8L V6 GM) (en: autotecnico-online.com).
NOTE: This tutorial complements the tutorial on how to test the ignition coil. You can find the ignition coil test tutorial here: How To Test The Ignition Coil -Step by Step (2.8L V6 GM).
You can find the ignition system circuit diagram here: 1991-1993 2.8L Chevy S10 Ignition System Circuit Diagram.
If you need to test the 8 pin ignition module, the following tutorial will help: How To Test The GM Distributor Mounted Ignition Module.
The following circuit wiring diagram may be of help: 1991-1993 2.8L Chevy S10 Ignition System Circuit Diagram.
Symptoms Of A Bad Ignition Control Module
To make this short, sweet, and to the point; the engine is not going to start due to a lack of spark and or fuel injection when the ignition control module (ICM) fails on your 2.8L v6 engine.
This is due to the fact that the ignition control module is in charge of:
- Activating the ignition coil to spark.
- Sending the fuel injection computer the crankshaft position to start injecting fuel (pulsing the fuel injectors).
This means that if your 2.8L equipped S10 (GMC S15) has spark and you can see the two throttle body fuel injectors injecting fuel, then the ignition control module (ICM) is OK and not defective.
What Tools Do I Need To Test The ICM?
As I mentioned at the beginning of this tutorial, you don't need an expensive automotive diagnostic test equipment to test the ignition control module (ICM). As a matter fact, you don't even have to remove it from the distributor to test it.
These are the tools you'll need:
- Multimeter that can read Volts DC and Volts AC.
- 12 Volt test light.
As you can see, nothing that'll break the bank. Now, in case you don't have a multimeter or need to upgrade yours, take a look at my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
Ignition Control Module Circuits
As you can see, the ignition control module has quite a few pins. Each one of these has a specific job to do. In this section I'm gonna' give you a very brief job description of each. This will give you an idea of what circuits we will be testing in the following pages of this tutorial.
- P: Pick-up Coil.
- N: Pick-up Coil.
- E: Ignition Control (IC).
- R: Ignition Control (IC) Reference High.
- +: Power (12 Volts).
- C: Ignition Coil Control (Switching Signal).
- B: Ignition Control (IC) Bypass.
On the ignition module itself, the only two terminals that we're going to worry about are the pick-up coil inputs. We'll be testing the pick-up analog voltage AC signal in TEST 3: Verifying The Pick-Up Coil's Signal.
TEST 1: Making Sure The ICM Is Getting Power
The very first thing that were going to do, is to make sure that the ignition control module (ICM) is getting power. This power is in the form of 12 volts.
These 12 volts come from the ignition coil. On the pink (PNK) wire of the black ignition coil connector.
You can use a 12 volt test light if you like to test for power, but for a more accurate test result I suggest that you use a multimeter. If you don't have a multimeter or need to upgrade yours, take a look at my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
NOTE: It's very important that before you start testing the ignition control module, you make sure that your 2.8L v6 engine is not starting due to a lack of spark. If the spark plug wires are sparking and the fuel injectors are injecting fuel, then you can conclude that the ignition control module is OK and not behind your engine's no start problem.
OK, these are the test steps:
Locate the pink wire of the black ignition coil connector (see photo above). This is the wire that feeds power to the ignition control module.
Both ignition coil connectors (black and gray) must remain connected to the ignition coil. The best way to test for the voltage inside the bank wire is using a back probe or a wire piercing probe. To see what a wire piercing probe looks like, go here: Wire Piercing Probe Review (Power Probe PWPPPPP01).
Connect the red multimeter test lead to the pink wire of the black ignition coil connector.
Connect the black multimeter test lead to the battery negative post.
With the key on but engine off, the pink wire should have 10 to 12 volts DC.
Alright, let's take a look at what your test results mean:
CASE 1: Your multimeter confirms that 10 to 12 volts are present in the pink wire. This is the correct and expected test result.
Now that we have confirmed that the ignition module is getting power, the next step is to check that the ignition module is creating the ignition coil's activation signal. For this test go to: TEST 2: Verifying The Ignition Coil Activation Signal.
CASE 2: Your multimeter confirms that 10 to 12 volts are MISSING in the pink wire. These missing 10 to 12 volts are what is causing the ignition module to not activate the ignition coil.
Your next step is to find out why these 12 volts are missing. Restoring this battery voltage will get the ignition module working again and the engine should start.
To further help you ignition control module troubleshooting efforts, you can find the ignition system circuit diagram here: 1991-1993 2.8L Chevy S10 Ignition System Circuit Diagram.