Ignition · Genuine GM Components
GM Ignition Components Hub: Spark Plugs, Wires, Coils & Fuel Injectors
A misfire, a rough idle or a flashing check-engine light usually traces back to one of four parts: the spark plug, the wire feeding it, the coil firing it, or the injector delivering fuel. Which of those your GM engine even has depends on its design — start there, and the right part gets much easier to find.
Browse Genuine GM PartsQuick Answer
Genuine GM spark plugs, plug wires, ignition coils and fuel injectors are sold through GM parts dealers such as Malouf Parts Xperts, as GM Genuine Parts and ACDelco. Order by VIN: GM engines differ in whether they use plug wires at all, whether coils sit on each plug or in a pack, and whether fuel is port- or direct-injected, and the VIN resolves the exact engine your vehicle was built with.
Which Ignition Parts Does Your GM Engine Use?
GM has used several ignition and fuel layouts over the past three decades. The family your engine belongs to decides what is on the parts list:
| Engine family | Coils | Plug wires | Fuel injection |
|---|---|---|---|
| Small-block V8, 4.8L to 6.2L (Silverado, Sierra, Tahoe, Yukon, Escalade) | One coil per cylinder, on the valve cover | Yes, short wires | Port on earlier engines; direct from the 2014 redesign |
| 3.6L V6, direct-injected versions (Traverse, Acadia, Camaro, Colorado and others) | Coil-on-plug | No | Direct |
| 2.0L turbo 4-cylinder (Cadillac CT4, CT5, XT4, XT5, XT6; Camaro, Malibu) | Coil-on-plug | No | Direct |
| 1.4L turbo 4-cylinder, first generation (2011–2016 Cruze; Sonic, Trax, Encore) | One coil cassette over all four plugs | No | Port |
| Older V6 designs such as the 3800 (Impala, LaCrosse and others) | Coil pack | Yes, full-length set | Port |
| Duramax diesel | None — compression ignition | No | High-pressure common rail |
Not every 3.6L is direct-injected: the earliest versions, including the one in the 2007 and 2008 Acadia and Enclave, used port injection, which is exactly the kind of split the VIN settles. Diesels have no spark plugs, which rules out a whole branch of misfire diagnosis.
Spark Plugs and Plug Wires
Spark plugs
Modern GM engines leave the factory with long-life iridium plugs, and the replacement interval ranges from 60,000 miles on several small turbocharged engines to 97,500 miles on the small-block V8s. Worn plugs do more than cost fuel economy: a wider gap asks the coil for more voltage on every firing, which is one reason plug and coil problems often arrive together. Our guide to AC Delco spark plug replacement intervals by GM engine lists the intervals and the conditions that call for changing them sooner.
Plug wires
Wires are not only a classic-car part. GM’s small-block V8s mount a coil for each cylinder on the valve cover and connect it to the plug with a short wire, and those boots sit close to the exhaust manifolds, where heat eventually hardens and cracks them. A cracked boot lets spark jump to ground, which shows up as a misfire on that cylinder. Our page on GM ignition wire sets, OEM fitment and failure symptoms covers which engines use them and how to tell a wire from a coil problem.
Ignition Coils
The coil turns 12-volt battery power into the high voltage that fires the plug. On most current GM engines each cylinder has its own coil, so a failing coil produces a misfire on one cylinder while the rest run normally. Coils fail from heat cycling, moisture getting into a cracked boot, and the extra load of worn plugs.
Symptoms
A single-cylinder misfire code (P0301 through P0308, where the last digit is the cylinder), rough idle, hesitation under load, and a flashing check-engine light when the misfire is severe.
The swap test
On engines with one coil per cylinder, move the suspect coil to a different cylinder and clear the code. If the misfire follows the coil to its new cylinder, the coil is the problem; if it stays put, look at the plug, wire or injector.
A flashing check-engine light means unburned fuel is reaching the catalytic converter. Driving on it risks overheating the converter, which turns a coil or plug repair into a far larger one. In New Jersey a lit check-engine light also means a failed inspection: gasoline vehicles from model year 1996 on are inspected through the OBD system, and an illuminated light fails the emissions test regardless of the code, per NJDEP.
The Cruze Exception: One Coil for Four Cylinders
The first-generation 1.4L turbo, used in the 2011–2016 Cruze and in the Sonic, Trax and Encore, does not use a coil per cylinder. A single coil cassette sits on top of all four spark plugs, so the swap test above does not apply: there is no second coil to swap with. A misfire on one cylinder (P0301 to P0304) still often traces to the cassette, but the fix is the whole unit. Replace the plugs with it, since worn plugs are a common reason the cassette failed, and check the valve cover for oil leaks, because oil pooling around the plug wells contaminates the boots and will shorten the life of the new cassette. The later, direct-injected 1.4L in the redesigned Cruze is a different engine, so confirm its coil layout by VIN before ordering.
Fuel Injectors
Injectors belong on an ignition list because a clogged or leaking injector produces the same single-cylinder misfire a bad coil does. Port-injected engines spray fuel into the intake runner; GM’s direct-injected engines spray it into the cylinder at far higher pressure, and their injectors come with seals and, on some engines, high-pressure lines that must be replaced rather than reused. Our comparison of AC Delco OEM and aftermarket fuel injectors covers flow matching, the parts an injector job needs, and how to tell injector trouble from ignition trouble.
Misfire Triage: Where to Look First
| What you see | Check first | Then check |
|---|---|---|
| Misfire code on one cylinder | That cylinder’s coil, using the swap test | Its plug, wire boot and injector |
| Random misfire code (P0300) across cylinders | Plugs past their interval | Vacuum leaks and fuel delivery |
| Misfire worse in rain or after a wash | Cracked coil or wire boots letting in moisture | Plug well sealing |
| Injector circuit code (P0201 to P0208) | The injector and its connector for that cylinder | Injector wiring |
| Hard start after sitting, fuel smell | A leaking injector | Fuel pressure |
Why the Specification Matters More Than the Brand Name
GM specifies each engine’s spark plug by heat range, gap, reach and electrode design, and those choices are matched to the combustion chamber and, on turbocharged engines, to the cylinder pressure under boost. A plug that threads in and looks right can still run too hot or too cold for the engine, and on a turbo engine the wrong heat range or gap is a common route to a misfire under load. The same logic applies to coils: output and boot design are matched to the plug and to how deep it sits in the head. Ordering the part GM specifies for your engine code is what removes that variable from the diagnosis.
What to Have Ready When You Order
Your VIN
On GM vehicles, the eighth character of the VIN identifies the engine. That single character is what separates, for example, a 5.3L from a 6.2L in the same truck.
The trouble code, if you have one
A misfire code names the cylinder, which tells us whether you need one coil or a set, and which bank a wire or injector sits on.
Mileage and history
When the plugs were last changed decides whether a coil order should include plugs, and whether a wire set is due at the same time.
Expert Tip: Replace the Plug With the Coil
When a coil fails on an engine with high mileage on its plugs, replace that cylinder’s plug at the same time, and consider the full set if they are near their interval. A worn plug raises the voltage the coil has to produce, and a new coil paired with an old plug is being asked to work harder from day one. On coil-on-plug engines the coil is already off, so the plug is only a few minutes more.
Ignition Parts Matched to Your Engine Code
Send us your VIN and the misfire code if you have one, and our parts counter in North Brunswick will confirm the engine, the ignition layout and the exact plugs, wires, coils or injectors it takes.
Get Ignition Parts Matched by VINGM Ignition Components FAQ
Where can I buy genuine GM ignition parts like spark plugs, wires, and fuel injectors?
GM parts dealers such as Malouf Parts Xperts sell genuine GM spark plugs, plug wires, ignition coils and fuel injectors, under the GM Genuine Parts and ACDelco names, and match them to your engine by VIN.
Do GM trucks still use spark plug wires?
Yes. GM’s small-block V8s in trucks and SUVs use one coil per cylinder mounted on the valve cover, connected to each plug by a short wire. Engines with coil-on-plug ignition, such as the 3.6L V6, do not use wires.
How do I know if an ignition coil is bad?
A bad coil typically sets a misfire code for one cylinder. On engines with a coil per cylinder, moving the coil to another cylinder and seeing whether the misfire follows it confirms the diagnosis.
Can a bad fuel injector cause a misfire?
Yes. A clogged or leaking injector causes a misfire on its cylinder that looks like an ignition fault. If the coil and plug check out, the injector for that cylinder is the next suspect.
Is it safe to drive with a flashing check-engine light?
A flashing check-engine light signals a severe misfire that sends unburned fuel into the catalytic converter. Continued driving can overheat and damage the converter, so the misfire should be addressed promptly.
Should I replace spark plugs when I replace an ignition coil?
It is good practice when the plugs have high mileage. A worn plug increases the voltage the coil must produce, so pairing a new coil with an old plug shortens the coil’s life.