P0307 on a Chevy Silverado indicates a misfire in cylinder 7 — the rearmost cylinder on the driver’s side, directly above the rear of the driver-side catalytic converter. Cylinder 7 is an AFM deactivation cylinder on 5.3L trucks, making AFM lifter failure a key consideration on high-mileage trucks.
Watch a cylinder-specific misfire traced to a failed ignition coil — worth ruling out the ignition side before assuming an AFM lifter on cylinder 7.
Cylinder 7 Location
Driver’s side cylinders front-to-rear = 1, 3, 5, 7. Cylinder 7 is the rearmost cylinder on the driver’s side — the fourth cylinder back on the driver bank. Accessibility is moderate — more cramped than front cylinders due to the firewall proximity, but manageable.
Common Causes and AFM Connection
On 2007–2021 5.3L trucks, cylinder 7 is one of the four AFM cylinders (1, 4, 6, 7). This makes failed AFM lifters a primary diagnostic consideration for P0307 alongside the standard coil and plug diagnosis. If standard coil/plug/injector diagnosis doesn’t resolve P0307 on a high-mileage 5.3L, suspect the AFM lifter before proceeding to compression testing — it’s far more common than a coincidental mechanical issue on an AFM cylinder.
On non-AFM trucks (GMT800, 4.8L, 6.0L, 6.2L), P0307 is purely a coil/plug/injector/compression issue — same diagnosis as any other cylinder.
Diagnosis Steps
Step 1: Swap the cylinder 7 coil to cylinder 5. If misfire moves to P0305, replace the coil. Step 2: Inspect and replace the cylinder 7 spark plug. Step 3: Test fuel injector. Step 4: On AFM 5.3L trucks — if steps 1–3 are clean, check for oil consumption and AFM-related symptoms (ticking on cold start, oil level drops). An AFM delete is the definitive fix. See: AFM delete guide. Related: P0300, P0305, P0301.
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