P0307 on Chevrolet: How to Diagnose & Fix

The 5.3L Vortec V8 with Active Fuel Management (AFM/DOD) in 2007-2013 Avalanches suffers from excessive oil consumption and premature lifter failure. The AFM system deactivates four cylinders for fuel economy, but the AFM lifters have a coating that wears off prematurely, leading to collapsed lifters, bent pushrods, fouled spark plugs, and catastrophic engine damage. GM issued TSB 10-06-01-008A for oil deflector installation but never recalled the vehicles. Oil consumption of 1 quart per 1,000 miles is commonly reported.

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.

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.

The EcoTec3 5.3L V8 (L83, and later L84 with Dynamic Fuel Management) uses Active Fuel Management to deactivate cylinders 1, 4, 6, and 7 under light load. The AFM lifters that collapse to deactivate those cylinders are prone to sticking or mechanical failure, often during a mistimed cylinder-mode switch event. A failed lifter stops actuating its valve, producing a loud ticking/tapping noise, rough idle, a flashing check-engine light, and a single-cylinder misfire (cylinder 7 is the most commonly reported). If a lifter disintegrates it can wipe the camshaft lobe, turning a lifter job into a cam-and-lifter job. Owners on CarComplaints report this surfacing anywhere from 80,000-120,000 miles, and it is the subject of multiple GM lifter/AFM lemon-law and class-action discussions.

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.

The Tahoe 5.3L and 6.2L V8 engines with Active Fuel Management (AFM) use collapsible hydraulic lifters that commonly fail between 80,000-120,000 miles. Failed AFM lifters cause misfires on deactivation cylinders (1, 4, 6, 7), ticking noises, and potential camshaft and cylinder wall damage. This is the same issue affecting the Silverado and Escalade. GM issued TSB #18-NA-077 acknowledging the problem. The VLOM (Valve Lifter Oil Manifold) must be replaced along with all 16 lifters.

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.

Automatic-transmission SS models with the 6.2L L99 V8 use Active Fuel Management lifters that are widely reported to collapse or stick, often leading to a misfire, valvetrain noise, and in many cases camshaft lobe damage. This problem is heavily documented across GM AFM-equipped V8 platforms and appears in Camaro owner complaints and forum repair threads. Repairs can become expensive because the cylinder heads and valvetrain must be opened, and many owners replace the cam and full lifter set once failure begins.