Ignition module failure is no joke because it often leaves you stranded. The complaint is the engine cranks normally, but does not start. The cause of an ignition control module failure is often associated with age and damage from heat buildup.
The correction for this issue becomes the replacement of the failed component. Here in this brief article we'll talk about three popular generations of control modules known for a high failure rate. This article focuses on General Motors automobiles from the last 30 years.
It even covers ignition module failure on the early DIS (Direct Ignition System) found on some of the most popular GM V-6 engines ever built. However, if you're Ford fan we created a separate article that focuses on the popular model Ford ignition module failure. We start on covering vehicles from the mid-80s and progress through the 2005 model year.
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Popular GM Ignition Control Module
The original equipment GM ignition control module can go a long way before it leaves you high and dry. When I say high and dry I'm talking about a vehicle that cranks around, but will not fire up.
Most of the original modules installed in Chevrolet distributors from the mid-80s through the mid-90s shared the same solid-state design. These made in the USA parts proudly show the ACDelco or GM symbol engraved on the module.
General Motors designed them to last for the life of the vehicle. However the 4.3 L V-6 and the 5.7 L V-8 engines that utilize the module lasted longer than many thought possible. It's not uncommon the find a Chevrolet Silverado 1500 pickup from the early 90s with more than 300,000 miles on the 5.7 L V-8 engine.
The same can be said for the Chevrolet Blazer or S-10 pickup truck that carries the 4.3 L V-6. These engines need ignition modules before they head to the junkyard. On a technical note, make sure you apply dielectric grease to the heat sink before you install the new part.
We have more on that below. Also make sure that the vent screen and the distributor isn't covered with corrosion. These old distributors let air in through the bottom and vent it through the top of the distributor cap. If these become clogged corrosion and heat buildup can cook the new module.
Chevy Ignition Module Failure 1996 through 2005
In 1996 General Motors redesign the ignition module discussed above. They used it on about 10 years worth of vehicles. With that said, these parts didn't hold up as well or as long as the ignition modules from the previous generation.
These parts found their way into the same V-8 and V-6 engines mentioned above. However, they now call them Vortec motors. Some popular vehicles with high sales figures carried these types of ignition modules.
Just to name a few, the Chevrolet Camaro Sport Coupe and all the sport-utility vehicles like the Tahoe, Suburban and Blazer. This also includes the pickup trucks and cargo vans. What's interesting about this common ignition module failure is the way it goes out.
As mentioned above, on the previous generation, you'd come out to the vehicle and it wouldn't start.
When the second generation modules go bad the vehicle starts up and runs good until it gets hot. At that point it stalls out and won't restart. After the engine cools down the vehicle might restart and run fine until it gets hot again.
This cycle happens over and over again until you replace the component. Intermittent malfunctions become hard to find, but the way this module fails is common knowledge around experienced mechanics. Sidebar: In some cases the Vortec plastic distributor fails before the ignition module.
Ignition Module Control Unit for Direct Ignition
In the early 90s General Motors started to do away with the distributor, cap and rotor we all loved since the turn-of-the-century.
GM decided they didn't need all those moving parts. Now they would receive data from a crankshaft and camshaft position sensor and use this information to fire each plug directly.
Hence, direct ignition became popular. On the V-6 engines like the 3100 and the 3800 series from General Motors, both used this early form of direct ignition. Three coil packs sit on top of the ignition module. Each coil pack fires two spark plugs at precisely the right moment.
The system worked extremely well and held up pretty good. As these vehicles started crossing the 15 to 20-year-old barrier the control module started to fail. The symptoms became wide range and included a no start condition as with the early ignition control module failure.
However, you get one telltale sign that signals the onset of direct ignition problems. We call it the jumping tachometer needle issue. On vehicles with factory installed tachometers the needle jumps or moves intermittently. Most people ignored these ignition module failure symptoms and continued to drive the automobile.
As the problem worsens these cars set random misfire codes in the P0300 range. Another code found set in memory with an ignition system malfunction is the P0336. This is a crank sensor code that sets when the crankshaft position sensor reports data out of range to the vehicles main computer or control module.
Final Thoughts about Ignition Control Module Failure
They designed these ignition control modules and GM V6 ignition coils to last for the life of the vehicle. Unfortunately, the definition of this term changed throughout the decades.
In the late 80s and early 90s people were putting about 15,000 miles a year on their automobiles in extreme circumstances. General Motors and other car companies thought that you should get rid of that car at the 200,000 mile mark.
Ignition Mobile Module App
In a strange twist of fate coupled with economic factors this standard became largely ignored by the general population. Now these automobiles are 15 to 20 years old with more than 300,000 miles on them in some cases.
After replacing my share of failed ignition control modules on a wide range of vehicles I'm learning that spending a little more money for a brand-name part might actually be worth it.
I've received some off brands made in China that didn't work right out of the box or failed within a couple of weeks. For this reason I a lean toward parts manufactured in North America or Mexico.
Another key factor of the durability of the replacement parts is applying dielectric grease to the heat sink. Although these replacement modules come with a small tube of dielectric grease you might want to opt for your own supply. I would rather apply too much of a high quality dielectric grease then not enough.
An ignition module is the component in electronic ignition systems that functions as the contact breaker for the coil or coils. In most basic terms, an ignition module is an electronic replacement for old, mechanical contact breakers like ignition points. These components are also referred to as 'ignition control units' and 'ignitors,' and their main purpose is to interrupt the flow of current through the primary winding of an ignition coil and create a high voltage pulse in the secondary winding. Since these modules are an example of solid state electronics, they aren't subject to the same sort of wear and tear that points suffer from, so they tend to have relatively long service lives.
Contents
- 2 How does an Ignition Module Work?
Ignition Module History
The first electronic ignition systems were experimented with in the late 1940s, but internal combustion engines continued to use point breaker ignition systems for several more decades. The first aftermarket electronic ignition system was offered in 1962, but these early systems were essentially designed to take some of the load off the points by using the points to activate a transistorized switching unit (the prototypical ignition module), which was then responsible for activating and deactivating the primary coil winding.
Throughout the early history of electronic ignition systems, ignition modules were used in two types of systems: breakerless, solid state ignition systems and in systems that still used mechanical points. For instance, Pontiac offered an optional breakerless system on some models in 1963, but other manufacturers (like Chrysler, for some 1967 Dodges and Plymouths) continued to use 'ignition amplifiers' in conjunction with mechanical points.
Some early electronic ignition systems used capacitor discharge ignition modules.
Chysler's first breakerless electronic ignition system debuted in 1971, and all of their vehicles were using it by 1973. This system was very similar to modern electronic ignitions in that it utilized a magnetic hall effect sensor instead of mechanical points and included a transistorized switching device (the ignition module.)
How does an Ignition Module Work?
Ignition modules are solid state switching devices that typically use a component like a transistor to switch the current flow through the primary winding of an ignition coil on and off. In that way, an ignition module works a lot like mechanical points. However, ignition modules are not able to do the job alone. Whereas points were mechanically operated by the rotation of the distributor shaft, an ignition module requires some type of external input in order to activate.
Electronic ignition systems typically use a transistorized switching mechanism.
Hall Effect Sensors
Most vehicles use a component known as a 'hall effect sensor' to activate the ignition module. In essence, a hall effect sensor is a device that produces a small current in response to a changing magnetic field. That makes it sort of like an electronic counterpart to ignition points.
Where ignition points physically open and close in response to the movement of an eccentric ring on the shaft of a distributor, a hall effect sensor produces a small current in response to the movement of a reluctor on the shaft of a distributor. As the reluctor rotates, it causes the hall effect sensor's magnetic field to expand and contract, which in turn generates a small current that is precisely timed to the rotation of the engine.
Breakerless Contact Breaking
Ignition modules vary in appearance from one application to another, but they all perform the same basic function.
In ignition systems that use a hall effect sensor and an ignition module, the electrical current from the hall effect sensor is what activates the ignition module. When the ignitor receives an input from the hall effect sensor, it uses a solid state component like a transistor to open and close a circuit that connects the primary winding of the ignition coil to the battery. This causes a magnetic field around the winding to expand and collapse, which produces high voltage pulses in the secondary winding. These pulses are then delivered to the spark plugs either via a distributor cap, rotor, and spark plug wires, or directly (in the case of distributorless ignition systems.)
Ignition Module Failure
When an ignition module fails, the engine will not start or run. This is due to the fact that the ignition module is responsible for activating the ignition coil, which itself is responsible for firing the spark plugs. In some cases, an inoperable ignition module can be traced to wiring or fuse problems, which is why it's important to make sure that the connections between the module and the battery, the module and the coil, and the module and the hall effect sensor are all good. If the ignition module isn't receiving battery voltage, after all, it can't complete (or break) the circuit to the coil.
Ignition modules can also fail internally due to heat and other stresses that build up over time. In some cases, an ignition module that fails like that will start to act up when it gets hot, which can cause sputtering or dying issues once a vehicle gets up to operating temperature. When a vehicle fails to start after a heat soak, or dies when the engine is hot, and then starts up just fine when cold, a bad ignition module may be suspected. However, it's important to test the module while the dying or no-start condition is present, as it may test good when cold.
Testing and Replacing an Ignition Module
Although replacing an ignition module is a relatively simple operating, testing these components can be a little more complicated. In general, you'll need to check to make sure that it's receiving battery voltage and that it is transmitting a signal to the coil when you crank the engine, but the exact test procedures can vary from one ignitor to another. There are professional tools that are specifically designed to test ignition modules, but there are typically also diagnostic procedures that you can follow with a more basic set of tools (like a multimeter and test light.)
Some ignition modules can be located by simply looking at the distributor, as demonstrated by this aftermarket GM unit.
Gm Ignition Module
Ignition modules are typically located on, inside, or near the distributor, but that isn't always the case. If you don't know where your ignition module is located, then you'll have to check a wiring diagram or manual to fin out before you can replace it. In some cases, you can also just take a look at your ignition system to find out where it is located. Some modules that are located inside distributor caps are actually visible by looking at the base of the cap, and in other cases you can simply trace the wiring harness that comes out of the cap, or the harness connected to the coil, to find the ignition module.
After you have located your ignition module and determined that it needs to be replaced, you will need to disconnect the battery. You can then disconnect the wires (or wiring harness) from the module and then unbolt it. In some cases, you will have to remove the distributor cap first.
Replacing an ignition module is a simple bolt-on type repair, but you may need to clean the mating surface and apply some dielectric grease. When this is necessary, you will typically find a tube of the appropriate material in the box that your replacement ignition module comes in. After that, you can simply bolt the new unit in place, plug it in, and reconnect the battery.
