P0305 on Chevrolet: How to Diagnose & Fix
Cylinder 5 Misfire Detected
6 Chevrolet models · 6 documented issues · 5 critical · $100-$7,500 repair
P0305 on Chevrolet by model: symptoms, diagnosis and fix
The fuel injector wiring harness on the Duramax diesel routes across the top of the engine under the valve covers. The harness rubs against the valve cover and rocker arms, causing the insulation to wear through and the wires to short or open. When an injector wire is damaged, the affected cylinder misfires, the engine runs rough, and white smoke pours from the exhaust. The chafing is accelerated by engine vibration and can affect multiple cylinders over time. GM released updated harness routing clips but the fundamental design has the harness in a high-wear location.
Common Symptoms
- Engine misfires on one or more cylinders
- White smoke from exhaust
- Rough idle that develops gradually
- Check engine light with injector circuit codes
- Engine runs on fewer than 8 cylinders
- Intermittent misfires that come and go
How to Fix
Remove the valve covers and inspect the injector harness for chafing (requires 2-3 hours labor). Damaged sections can be repaired with heat-shrink tubing and solder ($100-$300 for repair). If the harness is severely damaged in multiple places, a complete replacement harness costs $200-$500 and takes 3-5 hours to install. Add additional harness routing clips and protective loom to prevent recurrence. Some diesel specialists reroute the harness outside the valve cover (external harness conversion) to eliminate the chafing issue permanently.
Sources for this issue (1)
The 5.3L (and 6.2L) V8 with Active Fuel Management — GM's cylinder-deactivation system that drops the engine to 4 cylinders to save fuel — is notorious for collapsed AFM lifters. The special deactivating lifters (and the lifter oil-manifold/VLOM that feeds them) fail when oil pressure/timing to the lifter is compromised, causing the lifter roller to seize. A collapsed lifter no longer opens its valve, producing a dead-cylinder misfire, a loud ticking/tapping, rough idle and major power loss. If driven on, a collapsed lifter can wipe the camshaft lobe and destroy the cam, turning a lifter job into a top-end rebuild. This is consistently ranked the #1 Silverado engine problem and generates heavy forum and search traffic across the entire 2007-2019 AFM era. Disabling AFM (range tuner/AFM delete) is the common owner mitigation.
Common Symptoms
- Loud ticking or tapping from top of engine
- Cylinder misfire / rough idle
- Check engine light with misfire code
- Sudden loss of power
- Engine knock
- Excessive oil consumption alongside the tick
How to Fix
On a misfire/tick, pull the valve covers and inspect the AFM lifters and corresponding cam lobes. Standard fix is to replace all 8 AFM lifters (or convert to non-AFM lifters with an AFM-delete kit), the lifter guides, the VLOM/oil manifold, and head gaskets/bolts; if a cam lobe is wiped, the camshaft must be replaced too. Many owners install an AFM-disable tuner or a 'range' device to stop cylinder deactivation and prevent recurrence. Keep oil changes on time and avoid extended intervals — degraded/low oil pressure accelerates AFM lifter failure.
Sources for this issue (1)
The Active Fuel Management (AFM) and Dynamic Fuel Management (DFM) systems on the 5.3L and 6.2L V8 engines deactivate cylinders to save fuel by collapsing hydraulic valve lifters. These lifters have a complex locking pin mechanism that fails, causing the lifter to collapse and the affected cylinder to misfire. A collapsed lifter can also damage the camshaft lobe it rides on, turning a $300 lifter into a $3,000 camshaft and lifter replacement. The issue affects 2007+ Suburbans and is one of the most complained-about GM V8 problems. GM switched from 4-cylinder AFM to 17-pattern DFM in 2019, but lifter failures continue.
Common Symptoms
- Engine misfire on one or more cylinders
- Ticking or tapping noise from engine
- Check engine light with misfire codes
- Rough idle
- Reduced engine power
- P0300 random misfire or specific cylinder misfire code
How to Fix
Replace the failed lifter(s) and inspect the camshaft for damage. A single-side lifter replacement (one bank of 8 lifters) costs $1,500-$2,500 including labor. If the camshaft is damaged, add $500-$1,000 for a new cam and installation. Many owners opt to replace all 16 lifters and delete the AFM/DFM system with an AFM delete kit ($200-$400) and a custom tune that disables cylinder deactivation. This eliminates the root cause but requires a tuner ($400-$600). GM range device ($300) is a plug-in alternative that keeps all cylinders active without a tune.
Sources for this issue (1)
Vans built with the 6.0L L96/LC8 Vortec V8 (the volume engine in Express 2500/3500 from 2010 on) can break a rocker arm, producing an engine tick and a hard misfire on one cylinder. GM addressed it in preliminary information bulletin PIP5522B, which specifically lists 2017-2018 Chevrolet Express among the affected vehicles and warns that a broken rocker arm can let the valve drop into the cylinder and cause catastrophic engine failure. Important generation/engine discipline: the Express 4.8L L20 and 6.0L L96 do NOT use Active Fuel Management, so the AFM collapsing-lifter story that plagues Silverado/Tahoe 5.3L and 6.2L engines does not apply to these vans - this is a rocker/valvetrain hardware failure, not an AFM lifter failure. Owners typically hear a distinct top-end tick that does not go away as the engine warms, followed by a stored misfire code. A separate, narrower valve-spring concern (GM PIP5752A) applies only to engines built roughly June 1 through September 15, 2020, and also touched Express production.
Common Symptoms
- Persistent top-end ticking that does not quiet as the engine warms
- Single-cylinder misfire
- Rough idle
- Check engine light with random or cylinder-specific misfire codes
- Loss of power
- Loud clatter followed by catastrophic noise if the valve drops
How to Fix
Diagnose the ticking cylinder with a cylinder-balance test and stored misfire data, then pull the valve cover on the affected bank and inspect the rocker arms and pushrods before assuming a lifter problem. If a rocker is broken, replace the rocker, its pushrod, and inspect the valve, seat and piston crown for contact damage - a dropped valve means a head or short-block replacement. Catch it early: continuing to drive on a broken rocker is what turns a few-hundred-dollar rocker job into an engine. There is no recall or free remedy; PIP5522B is a service bulletin, not a warranty extension, so coverage depends on remaining powertrain warranty. For 2020-build engines, PIP5752A directs replacing all valve springs on both banks if no cylinder leakage is found.
Sources for this issue (3)
- GM PIP5522B / PIP5752A discussion - 6.0L L96 engine noise and misfire from broken rocker arm; Express listed among affected vehiclestsb
- GM Issues Service Bulletin PIP5752A for Faulty V8 Engine Valve Springs (springs used across the lineup including the Chevy Express van)tsb
- P0300 on 2014-2018 Chevrolet Express: Random Misfire Causes and Fixesarticle
A well-documented problem on the Atlas inline-five engines is dropped or loosened valve seats in the cylinder head, often after overheating or repeated thermal cycling. Owners report sudden misfires, rough running, low compression, flashing MIL, and in some cases complete loss of power. This issue appears in owner forums, repair discussions, and NHTSA complaints, and typically requires cylinder head replacement or machine work rather than simple ignition parts.
Common Symptoms
- rough idle
- flashing check engine light
- cylinder-specific misfire
- low compression on one cylinder
- hard starting
- loss of power
- engine shaking under load
How to Fix
Diagnosis usually starts with misfire codes, compression/leakdown testing, and borescope inspection if one cylinder shows very low compression. If a valve seat has moved or fallen out, the durable repair is removing the head and replacing it with an updated/remanufactured unit or having a reputable machine shop rebuild it. Ignition coils and plugs should only be replaced after confirming the misfire is not mechanical.
Sources for this issue (1)
The 1996+ 4.3L Vortec V6 uses a Central Sequential Fuel Injection (CSFI) 'spider' assembly under the upper intake plenum: a central injector body with flexible nylon tubes feeding poppet-valve nozzles at each intake port. Residual fuel bakes into varnish on the ball-to-seat face, so the poppets clog and, more importantly, lose their ability to seal, leaking fuel into the intake and opening at the wrong pressure. This is one of the most-documented S-10 4.3L driveability faults. GM issued warranty extension 99066F (to 10yr/200k mi) covering the poppet spray nozzles on 1996-2003 CSFI systems, confirming its prevalence.
Common Symptoms
- Hard starting / long crank (especially hot restart)
- Rough or shaky idle
- Random and cylinder-specific misfire codes
- Hesitation and loss of power on acceleration
- Fuel smell and drop in fuel economy
- Black smoke / flooding
How to Fix
Replace the CSFI spider assembly. The accepted permanent fix is the updated MPFI (multi-port) conversion spider, a direct-fit unit that uses conventional injectors with proper needle-and-seat sealing instead of the failure-prone poppets. A spider-plug/fuel-pressure test isolates a leaking poppet before replacement.
Sources for this issue (1)
P0305 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0305 mean on a Chevrolet?
P0305 stands for "Cylinder 5 Misfire Detected." This code means the engine control module detected a misfire on cylinder number 5, meaning that cylinder is not burning its air-fuel mixture properly on some combustion cycles. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder fails to fire correctly. A misfire wastes fuel, can make the engine run rough or shake, and dumps unburned fuel into the exhaust, which can overheat and damage the catalytic converter. It generally points to a problem with spark, fuel delivery, or compression specifically affecting cylinder 5. On Chevrolet it is documented across 6 models: Silverado 2500HD, Silverado, Suburban, Express, Colorado, S-10.
What are the most common causes of P0305?
The most common causes of P0305 are: Worn or fouled spark plug on cylinder 5, Failed ignition coil or coil pack for cylinder 5, Faulty or clogged fuel injector on cylinder 5, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire or boot (on applicable engines), Low compression from worn rings, valves, or head gasket, Carbon buildup or sticking valve on cylinder 5, Lean or rich fuel condition affecting the cylinder. The specific cause varies by vehicle.
How much does it cost to fix P0305 on a Chevrolet?
Published repair estimates on Chevrolet range from $100 to $7,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0305 on a different make?
View P0305 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.