P0301 Code on a GMC: Cylinder 1 Misfire Detected (GMC Guide)

P0301 on a GMC is "Cylinder 1 Misfire Detected." It names the exact cylinder the engine computer caught misfiring. Where cylinder 1 sits, and what usually goes wrong there, depends on which GMC engine you have. On a Sierra or Yukon small-block V8 with Active Fuel Management, cylinder 1 is one of the four cylinders GM shuts off to save fuel, which makes it a prime suspect for a collapsed AFM lifter. On a 4.3L V6 Sierra, an Acadia V6 or a Terrain four, cylinder 1 always fires. The surprise is that GM has written about cylinder 1 by name twice on GMC trucks: an oil-fouled #1 plug from a worn #1 cam bearing on the 2008–2009 Sierra and Yukon Hybrid, and fuel contamination that misfires cylinder 1 on deceleration on inline-engine Canyons and Envoys. This guide covers where cylinder 1 is on each GMC engine, the GM documents that name it, and the order to test in.

What Does P0301 Mean on a GMC?

The ECM reads crankshaft speed and expects a small push each time a cylinder fires. When the push from cylinder 1 goes missing often enough, it logs P0301. P0300 usually sets alongside it, because GM's monitor also records the overall misfire. If several cylinders are counting, start at our P0300 GMC hub. If cylinder 1 is clearly the worst, stay here. For the GM-wide basics on misfire codes, our P0300 GM guide covers how the monitor works.

Every gasoline GMC with OBD-II can set P0301: the Sierra, Yukon and Savana V8s and V6s, the Acadia and Terrain, every Canyon from the 2.8L four to the 3.6L V6, the Envoy, and the 2.7T in the Sierra 1500 and Canyon. The Hummer EV and Sierra EV cannot.

Where Cylinder 1 Is on Your GMC

Two companion patterns are worth watching. If P0301 shows up with P0304, P0306 or P0307 on a Sierra or Yukon V8, you're looking at the AFM cylinder group, not a lone coil. If it shows up with P0303 and P0305, the whole bank 1 is involved. On a 2018 Sierra or Yukon, GM's PIP5642 links bank-1 misfires to a failing high-pressure fuel pump lifter.

Is Cylinder 1 a Deactivating Cylinder on Your GMC?

This one question splits P0301 diagnosis in two.

• Yes — small-block V8 with AFM. GM's 20-NA-038 says these engines deactivate cylinders 1, 7, 6 and 4 in V4 mode. That covers the 2014–2018 Sierra and 2015–2020 Yukon with the 5.3L L83 or 6.2L L86, and the Sierra with the L82. GM's PIP4568S lists the same four cylinders for the 2007–2013 Sierra, 2007–2014 Yukon and 2006–2009 Envoy with AFM. Cylinder 1 has a special AFM lifter that can collapse or stick.
• Possibly — 5.3L L84 and 6.2L L87 with Dynamic Fuel Management. GM says DFM can deactivate any cylinder, so cylinder 1 is a switching cylinder like the rest. Most 2021 Sierra 1500 trucks with the L82 or L84 built from March 2021 carry RPO YK9: the hardware is there, but the ECM can't deactivate cylinders.
• No — 4.3L LV3. GM's 20-NA-038 says the V6 deactivates only cylinders 3 and 6. The LV1 in the Savana has no deactivation hardware at all.
• No — Acadia and Canyon V6. On the Gen 2 3.6L, the AFM cylinders are 2 and 5 (21-NA-036). Earlier V6s have no deactivation. A P0301 on a V6 points away from AFM hardware.
• No — inline engines and four-cylinders.

GM Bulletins That Name Cylinder 1 on GMC Models

2008–2009 Sierra and Yukon Hybrid: oil on the #1 spark plug

PIP4525D covers the 2008–2009 GMC Sierra Hybrid and Yukon Hybrid with the 6.0L LFA built before September 2, 2008. Oil deposits on the #1 plug make cylinder 1 misfire and set P0300 and/or P0301, typically after at least 8,000 miles. GM's explanation is excess oil splashing onto the #1 cylinder wall from a worn #1 cam bearing. GM's order is to inspect all plugs for oil fouling and cracked porcelain, then cylinder 1's valve seals, then the #1 cam bearing. If the bearing has spun, the engine is replaced.

Canyon and Envoy inline engines: cylinder 1 on deceleration

PIP3472C covers the 2006–2012 Canyon (2.8L LK5, 2.9L LLV, 3.5L L52, 3.7L LLR) and the 2005–2009 Envoy 4.2L LL8. GM says contaminated fuel "may cause a misfire on cylinder 1 during or shortly after deceleration," or on the opposite end cylinder during hard acceleration. These engines have a returnless fuel rail, so contaminants get trapped in the rail and pass through the #1 injector as the truck slows. GM's fix is to inspect and clean the tank, lines and rail, then clean the injectors. GM also warns that driving with contamination long enough leaves a sticking valve behind, which explains some repeat misfires after cleaning.

Sierra and Yukon AFM lifter on cylinder 1

PIP4568S describes misfire on cylinder 1, 4, 6 or 7, with or without a tick, from an AFM lifter that unlocks as soon as the engine starts or is collapsed. GM's test is the AFM compression test: if running compression on the misfiring cylinder stays below 25 psi whether the AFM solenoid is on or off, the lifter is at fault. For 2014–2018 Sierras and 2015–2020 Yukons with the L83 or L86, 15-06-01-002O carries the same story forward. If the valves don't move, GM replaces the valve lifter oil manifold and the AFM lifters on the affected bank — for cylinder 1, the driver-side bank.

A related document is easy to miss. PIP5083 covers 2007–2013 Savana, Sierra and Yukon trucks with the 4.8L L20, 5.3L LC9 or 6.0L L96 that misfire on cylinders 1, 4, 6 and 7 after a camshaft replacement. GM's tip is to check that the last four digits stamped on the end of the new cam match the box (5437 for the L20, 5436 for the LC9, 6660 for the L96).

2.7T Sierra 1500 and Canyon: P0301 with a tick

25-NA-037 covers the 2019–2025 Sierra 1500 and 2023–2025 Canyon with the 2.7L turbo. It lists P0301 through P0304 and P050D with a tapping noise from the cam carrier area. The cause is excessive play in an exhaust roller follower from needle-bearing axle pin wear. GM's rule: if one exhaust rocker has failed, replace the entire set, and inspect the exhaust camshaft for lobe wear.

Symptoms of P0301

• Check engine light, flashing during a heavy misfire
• A steady, rhythmic shake at idle; one dead cylinder is easy to feel on a V6 or four
• A light valvetrain tick on a Sierra or Yukon that doesn't change when injectors are cancelled (AFM lifter)
• Oil consumption with a wet, oily #1 plug (2008–2009 Hybrid pattern)
• A stumble as you coast to a stop on an inline Canyon or Envoy (fuel contamination pattern)
• Cold-start roughness that clears when warm on a V6 Acadia, Terrain or Canyon

Causes and How to Confirm Each

How Is P0301 Diagnosed on a GMC?

1. Confirm your engine RPO and locate cylinder 1 on the GM diagram, especially on a transverse Acadia or Terrain.
2. Record freeze frame: cold or warm, idle or load, decelerating or accelerating, and whether AFM was active.
3. Swap the coil, then the plug. If the misfire moves, you've found it.
4. Read the plug. Oil-fouled, wet with fuel or coolant, or cracked each send you down a different GM path.
5. Test the injector with a balance test.
6. On an AFM V8, run the AFM compression test and watch the valves before tearing into the engine.
7. On an inline Canyon or Envoy that misfires as it slows, look for fuel contamination before replacing ignition parts.
8. Run compression and leak-down if nothing above moves the misfire, then check your VIN for bulletins and recalls.

Parts and Cost

GM Documents That Name P0301 or Cylinder 1 on GMC Models

Have a dealer check your VIN for open recalls, bulletins and special coverages. The check is free.

NHTSA's summaries of some PIP4959 versions (the predecessor to 18-NA-115 for V6 Acadias, Terrains and Canyons) describe cold-start misfires "always on #1 cylinder." The current GM bulletin text says "one or two cylinders," so we treat that cylinder-1 wording as corroborated only.

What Other Pages Get Wrong

• "Cylinder 1 is always at the front of the passenger side." On every GMC small-block V8 and 4.3L V6, cylinder 1 is at the front of the driver side. On a transverse Acadia or Terrain V6 it's on the rear bank.
• "P0301 is just a coil." On an AFM Sierra or Yukon, cylinder 1 has a deactivating lifter. A coil swap that doesn't move the misfire should send you to GM's AFM compression test.
• "Clean the injector and you're done." On inline Canyons and Envoys, GM says contaminants sit in the returnless rail, and a sticking valve can remain after cleaning.
• Skipping the plug read. An oily #1 plug on a 2008–2009 Hybrid points to a cam bearing, a very different repair than a coil.

Frequently Asked Questions

Where is cylinder 1 on a 5.3L Sierra?

At the front of the driver-side bank. GM numbers that bank 1-3-5-7 from front to back and the passenger bank 2-4-6-8.

Is cylinder 1 an AFM cylinder on my Yukon?

On AFM engines (Gen IV V8s and the Gen V L83/L86), yes, along with 4, 6 and 7. On DFM engines (L84, L87), any cylinder can deactivate. Check your engine RPO on the glovebox label.

Can I fix P0301 by swapping coils myself?

The swap is the first test GM uses. If the misfire moves with the coil, replacing that coil is reasonable. If it stays on cylinder 1, the cause is plug, injector or mechanical, and further testing is needed.

My older Canyon misfires on cylinder 1 when I slow down. Why?

GM's PIP3472C describes exactly that on the 2006–2012 Canyon inline engines: contaminated fuel trapped in the returnless rail passes through the #1 injector during deceleration.

Does P0301 on a Sierra Hybrid mean the engine is bad?

Not automatically. GM's PIP4525D starts with plug and valve seal checks. Only a spun #1 cam bearing leads to engine replacement.

Should I replace all the plugs if one cylinder misfires?

If the plugs are near their service interval, replacing the set is sensible maintenance. It won't fix a lifter, injector or fuel contamination problem, so confirm the cause first. Our GM spark plug guide covers service intervals.