P0306 on Cadillac
Cylinder 6 Misfire Detected
P0306 on Cadillac vehicles indicates cylinder 6 misfire detected. Au7o has documented this code across 2 Cadillac models — most commonly on Escalade, XTS. This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. Typical repair costs on Cadillac range from $400 to $6,000, depending on the specific model and root cause.
Common Causes of P0306
- •Worn or fouled spark plug on cylinder 6
- •Failed ignition coil for cylinder 6
- •Clogged, leaking, or failed fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt valve, head gasket)
- •Damaged plug wire or coil connector
- •Carbon buildup or worn valvetrain components
P0306 on Cadillac by Model
Cadillac Escalade(1 issue)
- AFM/DOD Lifter Failure - V8 Cylinder Deactivation System2007-2020
AFM lifter collapse can affect engine-code-specific Escalades, but the original 2007-2020/5.3L-6.2L scope was too broad. Regular Escalades use active AFM in the 2010-2014 6.2L L94 and 2015-2020 6.2L L86; regular 2007-2009 6.2L L92/L9H applications did not operate active AFM, and DFM begins with the 2021 L87 outside this issue. The 2009-2013 6.0L Hybrid is a separate AFM application. Cylinders 1, 4, 6, and 7 are the designated AFM cylinders, but a tick or misfire still requires diagnosis because cam wear, oil-control faults, wiring, ignition, fuel, compression, and non-AFM valvetrain faults can produce similar symptoms.
Cadillac XTS(1 issue)
- 3.6L Direct-Injection Intake Valve Carbon Buildup2013-2019
The 3.6L V6 (LFX naturally-aspirated and LF3 twin-turbo) uses direct fuel injection, so no fuel washes over the backs of the intake valves. Combined with a PCV system that routes oil vapor into the intake tract, carbon coking accumulates on the intake valves over time. By roughly 60,000-100,000 miles this can cause rough idle, misfires, hesitation, and reduced fuel economy/power. This is separate from timing-chain-stretch and high-pressure fuel-pump issues; it is a fueling/airflow deposit problem inherent to GDI engines.
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View P0306 across all makes →Frequently Asked Questions
What does P0306 mean on Cadillac?▼
P0306 stands for "Cylinder 6 Misfire Detected." This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. On Cadillac specifically, this code is documented across 2 models.
What causes P0306 on Cadillac vehicles?▼
Common causes on Cadillac: Worn or fouled spark plug on cylinder 6, Failed ignition coil for cylinder 6, Clogged, leaking, or failed fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0306 on a Cadillac?▼
Repair costs on Cadillac range from $400 to $6,000, depending on the specific model and root cause.
Which Cadillac models have P0306 documented?▼
Au7o has documented P0306 on 2 Cadillac models: Escalade, XTS.