Short answer
AFM and DFM lifter failure usually shows up as a ticking noise, misfires and codes P0300–P0308. Repairs run from about $1,800 (lifters only) to $6,500 or more when the camshaft is damaged. A disabler reduces how often the lifters switch; it does not guarantee they won't fail.
What actually fails
An AFM or DFM lifter is two parts locked together by a spring-loaded pin. Oil pressure unlocks the pin to "collapse" the lifter and stop the valve from opening. Problems start when the lifter stays collapsed or sticks, when the locking pin or its spring breaks, or when the roller or its plastic guide wears. Keep driving and the stuck lifter can destroy the camshaft lobe above it. AFM engines have 8 of these lifters; DFM engines have 16.
Symptoms
- A ticking or tapping noise, often loudest at idle (some cold-start tick on 2019–2022 engines is normal per GM bulletin 19-NA-218).
- Misfires and a check-engine light with codes P0300 to P0308.
- Rough idle, shaking, loss of power.
- Sometimes no noise at all before the misfire.
Repair cost by severity
| What needs replacing | Typical range |
|---|---|
| Lifters (and guides) on one or both banks | From about $1,800 at a shop (labor alone often $1,000–$2,500) |
| Lifters + camshaft (+ often the oil manifold or valves) | Up to about $6,500 |
| Engine replacement | Can exceed $10,000 with labor (forum invoices) |
| DIY parts kit (lifters, guides, manifold) | About $380–$960 in parts |
Ranges come from repair guides, parts retailers and owner invoices; your local labor rate changes everything.
Which engines are concerned
Lifter complaints cover AFM engines from the 2007 Gen IV 5.3L through the L83 and L86, and DFM L84/L87 engines. GM issued technician bulletins for misfires due to collapsed lifters on 2021–2022 L84 and L87 engines built in particular periods, and a service update for broken locking-pin springs on trucks still in stock in late 2021. A class action over AFM/DFM lifters, Harrison v. General Motors, is pending in Michigan; we found no NHTSA recall for these lifters.
Can a disabler prevent it?
This is the reason most owners buy one, so here is what is and isn't known:
- For: keeping the engine on all cylinders sharply reduces lifter switch cycles (makers claim close to zero on classic trucks, and about 95% fewer for the BOOST DFM). Makers market this as protection, and many owners report peace of mind.
- Against: no independent study or GM statement shows fewer failures with a disabler. The special lifters stay in the engine, and some failures (worn rollers, broken guides) don't depend on switching. Owners have reported failures with a disabler installed.
Our wording: a disabler reduces deactivation cycles; it does not guarantee anything. Only a physical delete removes the AFM/DFM lifters.
Not the same problem: the L87 recall
In 2025 GM recalled about 600,000 vehicles with the 6.2L L87 (recall 25V-274), and NHTSA opened a recall query (RQ26001, January 2026) and an engineering analysis (EA26005, August 2026). That defect is in the crankshaft and connecting-rod bearings, not the lifters. A disabler has nothing to do with it.
Oil and maintenance points GM mentions
AFM is controlled by engine oil, so oil condition matters. GM bulletin 10-06-01-008 covers excessive oil consumption on Gen IV AFM engines and its fixes. After recall 25V-274, GM moved inspected L87 engines from 0W-20 to 0W-40 oil. Use the dexos oil and viscosity GM specifies for your engine, and many owners change it before the Oil Life monitor gets low.
Disabler, repair or delete?
If the engine is healthy, a disabler is the cheap, reversible way to stop the switching. If it already ticks or misfires, it needs a diagnosis and repair first; at that point some owners choose to replace the AFM/DFM parts entirely. We only cover plug-in disablers: see which fit your vehicle.
Questions owners ask
Will an AFM disabler stop my lifters from failing?
No one can promise that. It reduces how often the lifters switch, which owners and makers see as less stress, but no independent study measures the effect, and some failures (roller, guide) have nothing to do with AFM.
Is there a recall for AFM or DFM lifters?
We found no NHTSA recall for AFM/DFM lifters. GM issued technician bulletins, and a class action (Harrison v. General Motors) is pending. The 2025 recall of the 6.2L L87 is about crankshaft and rod bearings.
I already hear a tick. Will a disabler fix it?
No. A disabler doesn't repair a lifter that has already collapsed or stuck. Have the engine diagnosed first: a damaged lifter can wipe out a camshaft lobe.
Do DFM engines fail more than AFM ones?
There are no public failure rates. DFM uses deactivating lifters on all 16 positions and switches far more often; GM bulletins targeted 2021–2022 L84/L87 engines built in specific periods.
Sources
- Jalopnik: GM AFM/DFM lifter failure, how they work
- GM PIP5776 and PIP5861 (2021–2022 L84/L87 collapsed lifters), service update N212353840, bulletin 19-NA-218 (cold-start tick)
- GM bulletin 10-06-01-008 (AFM engine oil consumption)
- Harrison et al. v. General Motors, E.D. Mich. 21-cv-12927 (Berger Montague)
- Repair cost ranges: The Tools Trunk; SDPC AFM repair kit pricing; owner forum invoices
- NHTSA recall 25V-274 (L87 6.2L, crankshaft/rod bearings)