Chevy/GM check engine light overview.
General Motors — Chevrolet, GMC, Buick and Cadillac — has one of the largest installed vehicle bases in America, with the Silverado consistently among the best-selling vehicles in the country. That means a great many GM vehicles on the road, accumulating miles and occasionally lighting the dash.
The check engine light on a GM vehicle works exactly like any other OBD-II vehicle: a 1996-or-newer Chevy, GMC, Buick or Cadillac stores standard diagnostic codes that any scanner can read. The codes GM owners see are the common, standard ones — misfire, catalyst, fuel trim, EVAP, and transmission codes.
What is somewhat GM-specific is the distribution. GM's cylinder-deactivation system (Active Fuel Management, later Dynamic Fuel Management) and certain older automatic transmissions have well-documented patterns worth knowing about. But the first move is always the same: read the code before deciding anything. The light alone tells you nothing — a scan turns it into a specific code.
The codes GM owners see most.
Across the Chevrolet and GM lineup, these are the codes that come up again and again. Each links to a full diagnostic guide:
| Code | What It Means | Typical GM Cause |
|---|---|---|
| P0300 | Random / multiple misfire | Worn plugs, coils, or AFM-related on V8s |
| P0301-P0308 | Cylinder-specific misfire | Single coil or plug; lifter on AFM engines |
| P0420 | Catalyst efficiency below threshold | Aging catalyst or downstream O2 sensor |
| P0430 | Catalyst efficiency Bank 2 | Same as P0420, other bank on V6/V8 |
| P0171 | System too lean (Bank 1) | Vacuum leak, intake gasket, or dirty MAF |
| P0174 | System too lean (Bank 2) | Often paired with P0171 on V engines |
| P0455 | Large EVAP leak | Loose or worn gas cap — cheapest fix |
| P0700 | Transmission control system | Pointer code — common on older 4L60E trucks |
Chevy Silverado common codes.
The Silverado (and its GMC Sierra twin) is consistently one of the best-selling vehicles in America, so it represents a huge share of GM vehicles on the road. Common check engine causes:
- Misfire codes (P0300-P0308) — On the V8 engines, worn spark plugs and aging coils are the standard causes. On AFM-equipped V8s, a misfire localized to an AFM cylinder can point to a lifter issue — see the AFM section below. Confirm which physical cylinder using our misfire guides.
- P0420 / P0430 catalyst codes — Higher-mileage Silverados set catalyst codes as the converters age. With a V8 there are two catalysts and two possible codes.
- P0171 / P0174 lean codes — Vacuum leaks and intake gasket leaks as engines age. Lean codes can appear on either bank.
- Transmission codes — Older Silverados with the 4L60E automatic are well known for transmission issues. A P0700 on one of these points you to the TCM codes for the actual fault — see the 4L60E section below.
- EVAP codes — Gas cap first, as always.
Chevy Equinox common codes.
The Equinox is GM's volume compact SUV. Common check engine codes track with its 4-cylinder engines:
- Misfire codes — Coil and spark plug wear, the standard 4-cylinder causes. Certain Equinox 4-cylinder engines became associated with elevated oil consumption on higher-mileage examples, which can in turn contribute to misfires and related codes — diagnosis should start from the specific code.
- P0420 catalyst — Higher-mileage Equinox models set this as the catalyst ages. Test the downstream O2 sensor before condemning the converter.
- P0171 lean condition — Vacuum leaks and MAF contamination are the usual causes. Cleaning the MAF sensor is a cheap first step.
- EVAP codes — Gas cap and EVAP system components.
Chevy Malibu common codes.
The Malibu is GM's mid-size sedan. Common check engine codes on it:
- Misfire codes — Coil and spark plug wear, the standard 4-cylinder causes. A fresh set of plugs and a replaced coil resolves most.
- P0420 catalyst — Common on higher-mileage Malibus as the catalyst ages.
- P0171 lean condition — Vacuum leaks and MAF contamination. Worth inspecting the intake plumbing and cleaning the MAF.
- Turbocharged engine traits — Turbo Malibu engines have additional charge-air plumbing where boost leaks can develop, and direct injection brings intake-valve carbon over high mileage.
- EVAP codes — Gas cap first.
Chevy Cruze common codes.
The Cruze is GM's compact car, sold primarily with small turbocharged engines:
- P0171 lean codes — The turbocharged Cruze engines have a fair amount of intake and PCV plumbing, and these engines became known for lean codes from PCV system and intake-related leaks. The PCV components and intake seals are worth a careful inspection on a Cruze with a lean code.
- Misfire codes — Coil and spark plug wear, the standard causes.
- P0420 catalyst — Higher-mileage examples set this as the catalyst ages.
- Cooling-system-related codes — The Cruze's cooling system has several plastic components; cooling-related concerns are something Cruze owners encounter, and a thermostat-related code like P0128 can appear.
- EVAP codes — Gas cap and EVAP components.
Chevy Traverse common codes.
The Traverse is GM's larger three-row SUV, using V6 engines across its generations:
- Misfire codes — Coils and plugs again. With a V6, misfires are cylinder-specific and can appear on either bank.
- P0420 / P0430 catalyst codes — Two catalysts on the V6, so either bank's catalyst code can appear. Diagnose each independently.
- P0171 / P0174 lean codes — Bank-specific lean conditions. On a V6, an intake gasket leak on one bank can set a single-bank lean code.
- Timing-related codes — Certain GM V6 engines used in the Traverse and related models became associated with timing chain wear on higher-mileage examples, which can set timing-related codes. Any cam/crank timing code should be diagnosed properly rather than ignored.
- Transmission codes — A P0700 on a Traverse means reading the TCM codes for the real transmission fault.
The AFM and 4L60E stories.
Two GM-specific topics come up more than any others when owners search for help. Both are worth understanding.
Active Fuel Management (AFM)
Active Fuel Management — later succeeded by Dynamic Fuel Management — is GM's cylinder-deactivation technology. To save fuel, the system shuts down some of the cylinders on a V8 (or V6) under light load, running the engine on fewer cylinders, then reactivates them when more power is needed.
On certain AFM-equipped engines, particularly some older 5.3L V8s, the system became associated with two related concerns: elevated oil consumption and AFM lifter issues. A failing AFM lifter can cause a misfire on its cylinder, setting a cylinder-specific misfire code, and sometimes a ticking or knocking noise.
What this means for you as an owner:
- If you have an AFM V8 and a misfire code, a worn AFM lifter is one possible cause — but so are ordinary worn plugs and coils. Don't jump to the expensive conclusion. Read the specific code and diagnose properly using the swap-test method.
- Monitor your oil level regularly between changes on any AFM engine. Low oil makes lifter and related problems worse.
- A misfire that turns out to be a collapsed lifter is a more involved repair than a coil or plug — which is exactly why proper diagnosis before spending matters.
- Some owners with AFM concerns explore disabling the system, but that's a significant decision with its own trade-offs and emissions considerations — diagnose the actual fault first rather than assuming AFM is to blame.
The 4L60E transmission
The 4L60E is a GM automatic transmission used widely in older trucks, SUVs, and rear-drive cars. It's one of the most common transmissions on the road in GM vehicles from that era — and it has a well-documented history of wear-related issues as it accumulates miles.
Common 4L60E concerns include slipping, harsh or delayed shifts, and loss of certain gears. These typically set a P0700 code along with specific transmission codes in the TCM. The good news: not every 4L60E issue is a full rebuild. The actual fix depends entirely on the underlying TCM codes — it could be a shift solenoid, a sensor, or fluid-related, rather than a complete rebuild.
Questions GM owners always ask.
Plug an OBD-II scanner into the diagnostic port under the dash on the driver's side — any 1996-or-newer Chevy, GMC, Buick or Cadillac has this port. If you don't own a scanner, most auto parts stores read codes for free. Our guide to reading codes covers the options.
Active Fuel Management is GM's cylinder-deactivation system. On certain engines, particularly some older 5.3L V8s, AFM became associated with elevated oil consumption and lifter issues. A failing AFM lifter can cause a misfire and sometimes a ticking noise. If you have an AFM V8 with a misfire code, a lifter is one possibility — but ordinary worn plugs and coils are too. Diagnose the specific code before assuming the worst.
Not necessarily. P0700 is only a pointer code — it tells you the transmission module has stored codes, not what's actually wrong. Older GM trucks often use the 4L60E transmission, which has known wear issues, but the actual fault could be a solenoid, a sensor, or fluid-related rather than needing a full rebuild. Insist on having the specific TCM codes read before authorizing any major transmission work.
The small turbocharged engines in the Cruze became fairly well known for lean codes (P0171) traced to the PCV system and intake-related leaks. Have the PCV components and intake seals inspected carefully — a smoke test of the intake is the most effective way to find the leak. On the Cruze, this is a more common cause than on many other vehicles.
If the light is steady and the vehicle drives normally, short-term driving is usually fine while you get the code read and address it. If the light is FLASHING, that's an active severe misfire — stop driving, because it can damage the catalytic converter quickly. Either way, read the code soon rather than ignoring it.
It depends entirely on the code. Many common GM codes are affordable — a gas cap is a few dollars, an ignition coil is $30-100, cleaning the MAF is about $10. The expensive end is a catalytic converter, AFM lifter work, or major transmission repair. This is exactly why reading the specific code first matters — it tells you whether you're facing a cheap fix or a real bill.