P0304 Code on a Cadillac: Cylinder 4 Misfire Detected (Cadillac Guide)

P0304 on a Cadillac is "Cylinder 4 Misfire Detected." On an Escalade, that number matters. Cylinder 4 is one of the four cylinders GM's Active Fuel Management turns off on the small-block V8, and GM's PIP5259D names cylinder 4 by number for the 2015 Escalade 6.2L. It describes misfires on cylinders 4 and 6 from AFM lifters whose locking pins were damaged by aerated oil. On a 3.6L V6, cylinder 4 is a non-AFM cylinder on the bank GM ties to a leaking timing chain tensioner gasket. On a four-cylinder, cylinder 4 is the end cylinder, and the CT4 has its own GM bulletin. This guide covers where cylinder 4 is, what GM has documented for it, and how to test it.

What Does P0304 Mean on a Cadillac?

The ECM tracks crankshaft acceleration for each firing event and sets P0304 when cylinder 4's events fall short too often. P0300 typically sets with it. Every gasoline Cadillac with OBD-II can set P0304, because every Cadillac engine has at least four cylinders. For misfires spread across cylinders, see the P0300 Cadillac hub.

Where Cylinder 4 Is on Your Cadillac

On the V8, cylinders 4 and 6 sit next to each other on the same bank, and both are AFM cylinders. When P0304 and P0306 show up together on an Escalade, GM's bulletins point at the passenger-side AFM lifters, not two coincidental coil failures.

Escalade: The AFM Lifter on Cylinder 4

2015 Escalade 6.2L L86: PIP5259D

GM's PIP5259D (March 2015) covers the 2015 Escalade and the trucks built on it with the 5.3L L83 and 6.2L L86. Its condition reads: "SES light P0300, engine misfire on cylinder 4, 6 and/or tick noise." GM explains that an AFM lifter is mechanically collapsed or stuck "due to oil aeration" damaging its internal locking pin. The instruction is to check whether the valves move. If they don't, replace the AFM lifters and lifter guide on the bank with the concern, plus the oil pump pick-up seal. The seal matters because a leaking pick-up can pull air into the oil, and aerated oil is what damages the lifters. GM's bulletin labor for 2WD and 4WD Escalades was 11.7 and 12.8 hours. That shows how big a job this is.

2015–2020 Escalade: 15-06-01-002O

The later 15-06-01-002O covers 2015–2020 Escalades and 2016–2019 CTS-V LT4 with P0300 and a misfire or tick. It adds lifters stuck in their bores and bent pushrods to the list of causes. When the valves don't move, GM replaces the valve lifter oil manifold and that bank's AFM lifters. GM also says the guides must be replaced any time a lifter is. If the cam and lifters show heavy wear, the camshaft is replaced too. GM states the engine does not need to be replaced for this.

2007–2014 Escalade: the AFM compression test

For earlier AFM Escalades, PIP4568S (cylinders 1, 4, 6 and 7) gives the decisive test. If the misfiring cylinder's running compression stays under 25 psi whether AFM is commanded on or off, that cylinder's AFM lifter is collapsed or unlocking. GM also notes that a hot-idle oil pressure reading of 19 psi or less with fresh oil warrants testing the AFM pressure relief valve.

2021-and-later Escalade 6.2L L87

With Dynamic Fuel Management every cylinder can deactivate. 23-NA-043 lists P0304 for collapsed or separated lifters on 2021 Escalades built September 1, 2020 through March 31, 2021. Under 16,000 miles, GM replaces lifters and guides on both banks. Over 16,000 miles, it replaces only the affected bank, which for cylinder 4 is the passenger side.

3.6L V6: Cylinder 4 and the Left Bank

On the Gen 2 V6 (ATS, CTS, CT6, XT5, XT6 with LGX; CT5/CT6 3.0TT), cylinder 4 is not an AFM cylinder. GM's 21-NA-278 and PIP5486F tell technicians to check for damaged clips on the non-AFM rockers too. Their list of causes includes a left-bank timing chain tensioner gasket that doesn't seal. On these engines the left bank is bank 2, cylinders 2-4-6. GM's sequence is injector diagnosis, then cylinder cancellation, then intake valve carbon, then soft or spongy lash adjusters. After that come the rockers and the left-bank tensioner gasket.

A note on PIP5493: GM's investigation into a cylinder 4 misfire in that document concerned the 2017 Buick LaCrosse, not a Cadillac. The Cadillac model GM singled out in it was the 2017 XT5 on cylinder 6. See our P0306 guide.

Four-Cylinder Cadillacs: Cylinder 4 at the End

On the 2020–2025 CT4 with the four-cylinder engines GM lists as RPO L2R and L3B, 25-NA-037 covers a tapping noise from the cam carrier area with P0300 and/or P0301–P0304 and P050D. The cause is excessive movement in an exhaust roller follower from wear on its needle-bearing axle pin. On the 2.0T LTG, GM's PI1178F (cracked piston, low compression in one cylinder) and 19-NA-246 (coil boot carbon tracking on 2019 ATS/CTS) apply to cylinder 4 as much as any other.

Symptoms of P0304

• Check engine light, flashing when severe
• A steady valvetrain tick from the passenger side of an Escalade engine
• Misfire on cylinders 4 and 6 together (Escalade AFM pattern)
• Rattle or tap that changes with engine speed (V6 lash adjusters; CT4 roller follower)
• Rough idle and reduced power

Causes and How to Confirm Each

How Is P0304 Diagnosed on a Cadillac?

1. Identify the engine. On a V8, cylinder 4 is an AFM cylinder. On a V6 it is not. On a four-cylinder it is the end cylinder.
2. Check which other cylinders are counting. Cylinders 4 and 6 together on an Escalade narrows it to passenger-side AFM lifters.
3. Swap the coil and plug. On a V8, also check plug wire seating and the C-clip (PIP5159C).
4. Read hot-idle oil pressure on the scan tool with fresh oil.
5. Run GM's AFM compression test on V8s. Under 25 psi on cylinder 4 in both modes means the lifter.
6. Confirm valve movement with the passenger-side valve cover off before ordering lifters.
7. On a V6, follow 21-NA-278's order through the lash adjusters, rockers and left-bank tensioner gasket.
8. Verify the repair and check your VIN for bulletins and recalls.

Parts and Cost

GM Documents That Name P0304 or Cylinder 4 on Cadillacs

Have a dealer check your VIN for open recalls and bulletins. The check is free, and it is more reliable than any article, including this one.

What Other P0304 Pages Get Wrong

• "Cylinder 4 is on the driver side." On the Escalade V8, even cylinders are on the passenger side.
• "Lifters can be done one at a time." GM replaces the affected bank's AFM lifters and guides, and on early-mileage 2021 L87s, both banks.
• "New lifters are the whole fix." GM's PIP5259D also replaces the oil pump pick-up seal, because aerated oil caused the damage.
• "P0304 on a 3.6L Cadillac is an AFM problem." Cylinder 4 doesn't deactivate on the Cadillac V6.

Frequently Asked Questions

My Escalade has P0304 and P0306. Is that two problems?

Probably not. Both are passenger-side AFM cylinders, and GM's PIP5259D names exactly cylinders 4 and 6 with collapsed AFM lifters.

Is the AFM lifter repair an engine replacement?

No. GM's 15-06-01-002O says it isn't necessary to replace the engine. The lifters, guides, oil manifold and, if worn, the camshaft are replaced instead.

Does oil type affect AFM lifters?

GM lists low oil pressure, oil aeration and sludge as contributors to AFM lifter damage. Using the specified dexos oil and keeping it changed is cheap insurance, but it won't revive a collapsed lifter.

Where is cylinder 4 on a CT4 or XT4?

On an inline four, cylinder 4 is the last cylinder at one end of the head. Confirm which end on the GM diagram for your engine.

What does a P0304 tick sound like?

GM describes it as a consistent valvetrain tick at camshaft speed that doesn't go away when injectors are cancelled. That separates it from injector noise.

Can I keep driving with a collapsed lifter?

The misfire keeps unburned fuel going to the converter, and a damaged lifter can wear the cam lobe. Get it diagnosed rather than driving on it.