P0300 on a Chevrolet
Quick answer
On GM LS-family V8 engines, ignition coil failures and AFM/DOD lifter failures are documented common causes of random and cylinder-specific misfire codes, distinct from simpler four-cylinder misfire causes.
Severity 3 of 4. Short trips only.
Fix now · Short trips only
| Code | P0300 |
|---|---|
| Standard name | Random/Multiple Cylinder Misfire Detected |
| Make | Chevrolet |
| Severity | Fix now (3 of 4) |
| Safe to drive | Short trips only |
| Tool needed | Scanner with live data |
TOPDON TopScan Lite OBD2 Scanner, Bidirectional Scan Tool, 8 Resets & AI
Adds live sensor streams and freeze frame, which is what turns a code into a diagnosis rather than a guess.
Coverage varies by tool and by model year, so check a specific tool against a specific vehicle before buying.
What is different about P0300 on a Chevrolet?
GM's LS-family V8 engines have two well-documented misfire-related failure modes worth checking specifically: the coil-near-plug ignition design and the cylinder deactivation lifter system used on many of these engines.
Chevrolet specific patterns behind P0300
Coil-near-plug design failures: GM LS-family V8 engines use individual coils mounted near each spark plug, and these coils are documented to fail with age, producing misfire codes that can appear random if multiple coils are near end of life at similar mileage.
AFM/DOD lifter collapse causing misfire-like codes: Many GM LS-family V8 engines use Active Fuel Management or Displacement on Demand to deactivate cylinders under light load, and a documented pattern of lifter collapse or failure in this system can produce symptoms that register as a misfire code on the affected cylinders.
What to check first on a Chevrolet
The order below narrows the generic P0300 list down to what is worth checking first on this make. It is a starting order, not a diagnosis: patterns are generation specific and a vehicle outside those generations may have none of them.
Check in this order
- Check for a pattern connecting the misfire to specific cylinders associated with AFM/DOD deactivation if the engine uses that system
- Inspect or test individual ignition coils for failure
- Check spark plugs for wear or fouling
- Consider lifter or valvetrain noise as a sign of AFM/DOD-related mechanical failure rather than a purely ignition issue
The generic picture behind P0300
The computer counts tiny fluctuations in crankshaft speed between each firing event and uses them to detect when a cylinder fails to fire cleanly. This code sets when those misfire events are spread across multiple cylinders rather than concentrated on one, which points to a cause that affects the whole engine instead of a single spark plug or injector. A random misfire is often a fuel, air or ignition supply problem shared by every cylinder.
Everything on the main P0300 page still applies here. This page narrows the cause list to the patterns documented on Chevrolet vehicles, it does not replace the underlying definition.
The generic version of this code
Tools that can diagnose P0300
Adds live sensor streams and freeze frame, which is what turns a code into a diagnosis rather than a guess.
- LJPXHHU
OBD2 Bluetooth Scanner Car Code Reader for iOS, Android and Windows
- wireless
$13.98 Check pricePrices change often - Veepeak
Veepeak Mini Bluetooth OBD2 Scanner Code Reader for Android (NOT for iOS)
- wireless
$14.99 Check pricePrices change often - MOCATEC
WiFi ELM327 OBD2 Adapter WiFi ELM 327 OBD Scanner for Universal 12V Vehicle
- wireless
$15.95 Check pricePrices change often - UMEIJA
OBD2 Scanner Diagnostic Tool, Car Scanner for iOS & Android, Bluetooth 5.4
- wireless
$29.99 Check pricePrices change often
Common questions
What is AFM/DOD and why does it matter for misfire codes on a GM V8?
Active Fuel Management (AFM) or Displacement on Demand (DOD) is a system on many GM LS-family V8 engines that deactivates some cylinders under light load to save fuel. A documented pattern of lifter failure in this system can produce symptoms that register as a misfire code on the affected cylinders.
Are ignition coils a common cause of random misfire on GM V8 engines?
Yes, the coil-near-plug design used on GM LS-family V8 engines is documented to have individual coils fail with age, and since there are more individual coils than on some other ignition designs, multiple coils reaching end of life around similar mileage can produce what looks like a random misfire pattern.