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What P0305 means for your Chevy Silverado
Your Silverado's ECM detected that cylinder 5 isn't firing properly - the crankshaft position sensor saw the rotational speed dip slightly each time cylinder 5 was supposed to combust. On the 5.3L Silverado, P0305 is typically a cyl-5 coil failure (driver-side front) rather than an AFM issue - AFM deactivates cyls 1, 7, 4, 6 but NOT cyl 5, so a P0305 usually points to ignition rather than lifter.
🎯 Top Causes on the Chevy Silverado
55%
#1 CAUSE
Cylinder 5 Ignition Coil Failure
Cyl 5 is on the driver-side front of the 5.3L V8 - NOT one of the four AFM-deactivated cylinders. So if you see P0305, AFM lifter is far less likely than on P0301/P0304/P0306/P0307. The cyl-5 coil (ACDelco D510C / 12619161) typically fails between 90k-150k miles. The coil pack is right next to the exhaust manifold heat shield. Swap with cyl-3 to confirm. Aftermarket NGK U5023 or Delphi GN10570 are reliable.
OEM Coil
$60-$110
Aftermarket
$40-$70
w/Labor
$120-$240
25%
#2 CAUSE
Worn or Fouled Spark Plug
Silverado 5.3L L83 plugs (AC Delco 41-985 iridium) are spec'd for 100k-150k miles, but DI carbon contamination on the L83/L86 generation often shortens life to 80k. Cyl 5 plug is on the driver-side front - easy to access. Replace all 8 plugs as a set if one is worn (mixing causes repeat misfires). Gap to 0.040".
Plugs (set 8)
$60-$110
Tool
$10-$20
w/Labor
$140-$280
20%
#3 CAUSE
Intake Manifold or PCV Leak (Gen V)
2014-2019 5.3L L83 has known intake-manifold gasket and PCV system issues - vacuum leaks at the front of the engine can cause one cylinder (often cyl-5 on the driver-front) to run lean enough to misfire. Look for hissing at idle, oily residue near the intake-to-head joint, or unusually high long-term fuel trim values. Replace the PCV/intake gasket.
Intake Gasket
$25-$60
PCV Valve
$30-$80
w/Labor
$180-$380
🚗 Most Affected Silverado Model Years
| Year | Engine | Primary Cause | Typical Mileage | Notes |
|---|---|---|---|---|
| 2007-2014 | 5.3L LMG (Gen IV) | Coil pack | 90k-150k | Not an AFM cylinder |
| 2014-2019 | 5.3L L83 (Gen V DI) | Coil + plug | 80k-130k | DI carbon at 80k+ |
| 2019-2020 | 5.3L L84 (DFM) | Coil | 40k-90k | DFM, not AFM, on cyl 5 |
| 2014-2020 | 6.2L L86/L87 | Coil | 80k-140k | Same coil architecture |
🔧 How to Diagnose P0305 on a Chevy Silverado
- Swap cyl-5 coil with cyl-3 (also driver side, easy access). Clear code, drive. If misfire follows = bad coil. Because cyl 5 is NOT an AFM cylinder, a stationary misfire is almost always ignition rather than lifter.
- Pull the cyl-5 plug and inspect. Replace all 8 plugs as a set if mileage is over 80k. Gap to 0.040" with AC Delco 41-985 iridium.
- If coil and plug are good, check intake manifold for vacuum leaks. Spray carb cleaner around the intake-to-head joint and PCV at idle. If RPM changes, you have a leak. Replace gasket or PCV.
Want a step-by-step walkthrough specific to your Chevy Silverado? Run a $5.99 AI diagnosis report - we narrow the cause to your year, engine, and symptoms.
❓ Frequently Asked Questions
Can AFM cause P0305 on a Silverado?
Very unlikely. AFM deactivates cyls 1, 7, 4, 6 on the 5.3L - cyl 5 stays active in all modes. P0305 with a sewing-machine tick is unusual; P0305 alone almost always points to ignition (coil or plug). If you do see P0305 + tick, get a deeper inspection - it may be a non-AFM lifter that has worn its cam lobe.
How much does P0305 cost to fix on a Silverado?
Coil (DIY): $40-$110 in parts. Shop: $120-$240. Plug set (DIY): $60-$110 + 1 hour. Intake gasket: $180-$380 at a shop. Most P0305 cases are coil swaps under $250 total.
Which cylinder is cylinder 5 on a Silverado V8?
GM small-block V8s number 1-3-5-7 on driver side, 2-4-6-8 on passenger side. Cyl 5 is the third from the front on the driver side - reasonably easy to access. The closest neighbor is cyl 3 (also driver side) for a coil-swap test.
Should I do an AFM disabler even if my P0305 is just a coil?
If your truck has under 80k miles AND it's a 2014-2019 L83 or 6.2L L86, yes - a Range Technology AFM disabler ($170) is cheap insurance against the AFM-cylinder lifter failures (which would show as P0301, P0304, P0306, P0307). Fixing cyl-5 misfire doesn't protect against future AFM-related failures.
Can a flashing CEL on P0305 damage the engine?
A flashing CEL means severe misfire - raw fuel dumping into the cat damages the catalytic converter ($1500-$2500 on Silverado) within a few hundred miles. The misfire itself won't damage the engine internals immediately but will accelerate plug and coil wear on adjacent cylinders. Pull over and address ASAP.
See all P0305 causes (all vehicles) → · Related: Chevy Silverado Intake Manifold Leak →