The Chevy truck is one of the most popular vehicles on the market today. It is reliable and affordable, which makes it perfect for those who want to get involved in off-road activities. The Chevy truck comes in several different models, depending on the type of vehicle. Some of the more popular models are the Silverado 1500, Colorado, and Canyon.
However, when the Active Fuel Management system (AFM) was launched in 2007 in Chevy Silverdos 5.3L engines, it started causing different problems in Chevy vehicles from 2007 to 2011 that could also turn on check engine light. Despite the exceptional build quality, performance, and reliability, AFM in Chevy engines has been disappointing due to some serious reasons.
In this guide, we will Chevy models of all those years that had problems with Active Fuel Management.
Before diving further, I have crafted a detailed guide on identifying Active Fuel Management. I would highly recommend you read that guide first before proceeding further.
What You Will Learn:
What are Some of the Chevy AFM Problem Years?
From 2007 to halfway of 2011 Chevy trucks have the biggest problems with AFM. The common issues with 5.3L AFM engines were excessive oil consumption and AFM lifter failures.
AFM lifter is an important mechanical component that should smoothly work in AFM engines. However, due to excessive oil consumption or bad oil quality, the AFM lifter experiences a lot of wear and tear, due to which it collapses and causes noise in the engine.
There really don’t seem to be the issues with AFM engines after 2014 as there were in 2007-13. Of course, it can still fail but it’s much more dependable than it used to be.
Is your Chevy struggling to accelerate? You can read my guide on why Chevy is losing power when accelerating.
5.3 AFM Years
GM introduced AFM in 2007 in GMT900 trucks with a 5.3L engine. GMT900 were the new body style trucks, also called 2007.5. In 2014, all the GM motor choices had AFM.
Common Chevrolet AFM Problems
Here are some of the Chevy AFM problems that plagued my Chevy Silverado truck:
1. Excessive Oil Consumption
Excessive oil consumption was the most serious problem for Chevys from 2007 to 2011 years. For warranty purposes, GMC usually considers it excessive oil consumption when the engine uses more than 1 quart of oil in 2000 miles or less. If your engine is consuming more than that, there can be certain issues.
In Chevy engines with AFM, the oil gets past the pistons and enters the combustion chamber where it is burned out and forms carbon deposits around piston rings oil grooves and cylinder walls.
In Chevy Silverados with AFM, there is a pressure relief valve in the oil pan. The valve controls the oil pressure when the engine is operating in V4 mode by discharging the extra oil. The oil spray from the pressure relief valve is pulled through the PCV system to the engine air intake manifold.
In 2011, GMC introduced a new valve/rocker cover design for the driver side in which the PCV drain hole has been relocated to prevent oil from entering the intake manifold. Inspect the intake manifold to see if there is any oil puddling in the bottom. If it is, you need to replace the valve cover. This valve cover is for 2009-2011 GM engines and this one for 2007-2009 engines.
If the piston rings of your engine are sticking with carbon deposits due to the excessive oil burning, you should clean them. You need to remove the spark plug and make sure that the piston is at the top dead center (bottom of the cylinder).
You can clean the pistons with 4-5 oz of Upper Engine and Fuel Injector Cleaner, GM P/N 88861803 in each cylinder. Allow the material to soak for at least 2.5-3.0 hours, and then remove the cleaner.
A suggested method of removing the cleaner is cranking the engine over with the harmonic balancer bolt. Make sure to unplug the ignition coils and fuel injector before cranking the engine over.
In 2013, GM introduced another fix to install AFM shields on all non-hybrid models. All you need to do is to remove the oil pan of your vehicle. You will find the AFM relief valve (1) on the oil pan as shown in the figure below:
Install this AFM shield on the relief valve and tighten the oil pan with a torque wrench by applying a torque 28N-m. With this deflector, all the oil spray coming out of the AFM relief valve will be deflected back to the oil pan.
Also, in 2014, GM introduced a variable displacement pump that changes oil flow based on demand. Dual pressure-control of an oil pump enables operation at a very efficient oil pressure at lower rpm coordinated with the Active Fuel Management.
In this way, less oil will be consumed when the vehicle is being operated in V4 mode. Moreover, the oil capacity was also increased in engines after 2014 to improve lubrication.
Low Oil Pressure Message
A low oil pressure message/light became a common complaint on 2007-2016 GM vehicles with AFM. Oil lifters require 22psi of pressure to release the locking pins when AFM is activated.
If there is low oil pressure, AFM lifters will not properly work. In that case, you should first inspect the AFM valve lifter oil filter screen (located beneath the oil pressure sensor) for evidence of any sludge. You can find the filter on the valley cover.
If the filter screen is clogged, it will restrict the oil flow to the oil pressure sensor and will indicate low oil pressure. You can clean the AFM VLOM lifter screen filter with the brake cleaner.
Oil pump failure in engines with AFM can also be the cause of low oil pressure problem. GM has encountered numerous oil pump failures with the 5.3L engines produced from 2007-2013, resulting in a loss of oil pressure due to sticking pressure regulating valves.
If the pressure regulating valve is stuck open, it will return oil to the suction side of the oil pump, resulting in a low or no oil pressure condition. If the valve is stuck close, an over-pressurization condition can occur, causing the filter to become distorted or the gasket/seal to dislodge.
In GM engines 2007-2013, an oil pump is mounted on the front of the engine and is driven off the crankshaft at twice the speed of a camshaft-driven pump.
The oil pump is operating on unfiltered oil. The debris in the oil can restrict the movement of the pressure regulating valve in the oil pump, causing it to stick.
When dealing with low oil pressure in GM engines with AFM, you should look at the following key areas of the oil pump:
- A restricted inlet screen on the pick-up tube in the oil pan is blocking the oil flow.
- If the O-ring that seals the pickup tube to the oil pump is not properly sealed or has a slit in it, cavitation can occur due to air leakage, resulting in a low or no oil pressure condition.
AFM Lifter Noise
Due to low oil pressure or excessive oil consumption, AFM lifter failure is also a big problem in GMC engines with Active Fuel Management.
Low oil pressure results locking pin inside the lifter not fully retracting upon AFM activation. Eventually, the locking pin would get sheared off so badly that it could not prevent the lifter from collapsing anymore.
If an AFM lifter is mechanically collapsed or stuck, low compression will be found on that cylinder during an AFM compression test. In such cases, your engine control module will throw a P0300 trouble code, meaning “Random or Multiple Cylinder Misfire Detected” and also turn on check engine light.
This AFM lifter collapse may be the result of internal locking pin damage, which may occur if the response time of an AFM lifter unlocking event is decreased due to
- Low oil pressure
- Internal engine sludge
- Lifter guide
- Lifter bore
- Cam lobe wear
If the AFM lifter bore is lightly worn, it will bleed off enough oil pressure to prevent the AFM lifter from unlocking. Make sure the lifter bore should have a spec of .843 -.844″.
Similarly, AFM lifter guides hold the AFM lifter in place and line it correctly in its notches so that it does not rotate and gets stuck with the cam lobes. It is the camshaft that pushes the locking pin of the lifer when it comes into contact with the lifter roller.
AFM is activated and deactivated at the cam base so that when the engine switches from V4 to V8 mode, it is unnoticeable to the driver. If the AFM activates or deactivates on the camshaft peak or camshaft ramp, the lifter will stuck compressed and will also damage the cam lobes.
In 2019-2021 (March) Chevy vehicles, AFM lifters had gone even worse that the vehicles seem to be failing under 10,000 miles.
One user says this:
“6,272 miles on my 2021 Trail Boss and it’s in with a failed lifter right now. Seems a bit early for this type of major failure.”
Another user says this:
“2020 Silverado 5.3- Knocking, check engine (emissions warning), Service ECS, parking brake. Took it in this morning and haven’t gotten the official diagnosis yet, but the technician said this combination sounds like lifter failure. I bought the truck several months ago with 8k.”
It was found that during the assembly of Chevy vehicles after 2019, a batch of bad lifters was used. The locking pin was sheared, due to which it could not lock in a fixed position.
Changes In Exhaust Tone
In GM engines with Active Fuel Management, exhaust tone changes and you could hear exhaust drone-type noise when AFM activates.
When Active Fuel Management is enabled, physical changes take place within the engine, allowing it to run in a 3-cylinder or 4-cylinder mode with accompanying additional fuel savings.
The change in exhaust tone is expected, as all sound from the exhaust is the result of combustion in the engine.
If there is an excessive drone-type noise from the exhaust of the GMC engine when in V4 mode, you should perform an exhaust leak test. You can consult this pdf to learn more.
How to Disable AFM Without a Tune?
To disable AFM without tuning AFM, you would need an AFM delete kit that replaces AFM cams, lifters, valley cover, and gasket. This method is costly but saves the engine from further damage.
Disabling AFM With Disabler
A cheaper alternative to get rid of Active Fuel Management is to get Range Disabler that tunes the ECM by plugging into the OBD-II port under the dashboard and turns off its ability to send signals to VLOM to operate AFM lifters. However, this method would not remove any residual chance of failure of lifters.
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