P0306 on 2010-2013 Cadillac Escalade EXT: Cylinder 6 Misfire Causes & Fixes

What's Unique About the 2010-2013 Cadillac ESCALADE EXT

The 6.2L L94 V8 engine used in this generation of Escalade EXT features Active Fuel Management (AFM), a system designed to improve fuel economy by deactivating four cylinders (1, 4, 6, and 7) under light load. Unfortunately, the hydraulic lifters used in this system are a well-documented weak point and are prone to failure. A collapsed or stuck AFM lifter is a very common cause for a persistent single-cylinder misfire (like P0306) on this specific platform. This is a much more involved and expensive repair than a typical ignition component replacement and may also cause damage to the camshaft if not addressed.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Rough or vibrating idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Solid or flashing Check Engine Light
• Decreased fuel economy
• Engine may make a ticking or tapping sound, especially if the cause is a bad lifter. This is a key symptom pointing towards AFM failure.
• Service StabiliTrak warning message may appear on the dash along with the CEL.

Most Likely Causes

1. Loose or Damaged Spark Plug Wire 🔴 High Probability A manufacturer TSB (#PIP4819A) specifically calls out inspecting and replacing loose spark plug wires as a fix for P0300-P0308 misfire codes on this vehicle.
   How to confirm: Visually inspect the spark plug wire for cylinder 6. Ensure it is securely connected at both the ignition coil and the spark plug. Check for any signs of damage, arcing (white marks), or corrosion. The wire should 'click' into place on both ends.
   Typical fix: Reseat or replace the spark plug wire. It is often recommended to replace all wires as a set, especially on higher mileage vehicles.
   Est. part cost: $50-$100 for a quality set of wires.
2. Worn or Fouled Spark Plug 🔴 High Probability
   How to confirm: Remove the spark plug from cylinder 6. Inspect it for wear on the electrode, carbon buildup, or oil/fuel fouling. A wet, fuel-smelling plug can indicate a lack of spark or a stuck injector. You can swap it with a plug from another cylinder (e.g., cylinder 4) and see if the misfire code changes to P0304.
   Typical fix: Replace the spark plug. It is best practice to replace all 8 spark plugs at the same time. The factory recommended gap is 0.040 inches, and iridium plugs should not be re-gapped.
   Est. part cost: $8-$20 per iridium spark plug.
3. Failed Ignition Coil 🔴 High Probability
   How to confirm: Swap the ignition coil from cylinder 6 with a coil from another cylinder (e.g., cylinder 2). Clear the codes and run the engine. If the code changes to P0302, the ignition coil is faulty.
   Typical fix: Replace the failed ignition coil. They are held on by two bolts and are easily accessible.
   Est. part cost: $35-$75 for one OEM-quality coil.
4. Failed Active Fuel Management (AFM) Lifter 🟡 Medium Probability The 6.2L L94 engine's AFM system lifters are a known common failure point. The lifter can become stuck or collapse due to internal pin damage, often related to oil aeration or pressure issues, preventing the valve from opening and closing properly. This is a widely discussed issue in owner forums.
   How to confirm: This is a more advanced diagnosis. A classic symptom is a persistent ticking or tapping noise from the engine that sounds like a loud clock. A mechanic can perform a cylinder deactivation test 🎬 See this guide for diagnosing AFM lifter failure and ticking. with a professional scan tool or remove the valve cover to physically observe if the rocker arms for cylinder 6 are moving. Low compression on cylinder 6 after ruling out ignition/fuel issues strongly points to a mechanical problem like a lifter.
   Typical fix: This is a labor-intensive repair that involves removing the cylinder head to replace the failed lifter(s) and often the camshaft, which can be damaged by the failed lifter. Many owners and shops opt to install an 'AFM delete kit' at this time to prevent future failures. This involves replacing the AFM lifters with standard lifters, replacing the camshaft, and reprogramming the ECM to disable AFM.
   Est. part cost: $200-$500 for lifters and gaskets, but labor is significant, often 10+ hours. An AFM delete kit can cost $300-$700+.
5. Clogged or Faulty Fuel Injector ⚪ Low Probability
   How to confirm: Swap the fuel injector from cylinder 6 with one from another cylinder. If the misfire code follows the injector, the injector is the problem. A professional can also perform a fuel injector balance test with a scan tool.
   Typical fix: Replace the faulty fuel injector.
   Est. part cost: $50-$120 for one injector.

Rare But Worth Checking

• Low Engine Compression: Beyond a failed lifter, low compression can be caused by worn piston rings, a burnt valve, a broken valve spring, or a damaged cylinder head gasket. A compression test is required for diagnosis.
• Intake Manifold Gasket Leak: A vacuum leak near the intake runner for cylinder 6 can lean out the air/fuel mixture and cause a misfire. This would often be accompanied by a lean code like P0171 or P0174.
• Corroded Engine Ground Strap: A poor ground connection between the engine and chassis can cause weak or erratic spark, leading to misfires. One ground is located on the rear of the driver's side cylinder head.
• Blocked Oil Passages: Dirty or sludged oil can block the narrow oil passages leading to the AFM lifter or deactivation solenoid, causing it to malfunction and trigger a misfire.

Diagnosis Steps

1. Confirm the code P0306 with an OBD-II scanner. Note if the Check Engine Light is solid or flashing and check for any other codes, especially P0300 or P3441.
2. Inspect the spark plug wire for cylinder 6 (third from the front on the passenger side). Ensure it is fully seated on the coil and plug. Check for damage. This is a specific TSB recommendation.
3. Swap the ignition coil from cylinder 6 with another cylinder (e.g., cylinder 4, second from front on passenger side). Clear the codes and drive. If the code changes to P0304, the coil is bad.
4. If the misfire remains on cylinder 6, remove and inspect the spark plug. Look for wear, fouling, or damage. A wet plug suggests a fuel or spark issue. Replace if necessary, or swap with another cylinder to see if the code follows.
5. If ignition parts are confirmed good, listen for a distinct ticking/tapping sound from the engine, which is a strong indicator of a failed AFM lifter.
6. Check engine oil level and condition. Low or dirty oil can cause issues with the hydraulic AFM system.
7. If the cause is still not found, more advanced diagnostics are needed. This includes testing the fuel injector, performing an engine compression test on cylinder 6, and checking for vacuum leaks.
8. If compression is low, the issue is mechanical. Remove the valve cover to inspect for broken valve springs or bent pushrods. If valve train movement is incorrect, the problem is likely a failed AFM lifter, requiring professional service.

Parts You'll Likely Need

• Spark Plug (OEM #41-162) — Spark plugs are a routine maintenance item and a primary cause of misfires. The original equipment is an ACDelco Iridium plug. The gap should be pre-set to 0.040" and not adjusted.
  Trusted brands: ACDelco, NGK, Denso
  OEM price range: $12-$20
  Aftermarket price range: $8-$15
• Ignition Coil (OEM #12611424) — The coil-on-plug ignition coils can fail over time, causing a misfire on a single cylinder. Part number 12611424 is a common replacement for the original 12570616.
  Trusted brands: ACDelco, Delphi, Standard Motor Products
  OEM price range: $35-$75
  Aftermarket price range: $25-$50
• AFM Lifter (OEM #12645725) — The Active Fuel Management lifters are a known failure point on the L94 engine, leading to misfires. If one has failed, it's common practice to replace all AFM lifters (8 total) at the same time. The original lifters have been superseded by newer part numbers.
  Trusted brands: ACDelco, Elgin, Melling
  OEM price range: $30-$50 per lifter
  Aftermarket price range: $20-$40 per lifter
• Fuel Injector (OEM #12609749) — A clogged or electrically failed fuel injector will cause a misfire on its corresponding cylinder. The L94 engine is FlexFuel capable, which requires a specific type of injector.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $50-$120
  Aftermarket price range: $30-$80

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or starting to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0306. This is common with AFM lifter issues.
• P3441 — This code stands for 'Cylinder 6 Deactivation/Intake Valve Control Circuit/Open'. It directly points to a problem in the AFM control system for cylinder 6, such as a faulty deactivation solenoid, wiring issue, or low oil pressure. It strongly suggests the P0306 misfire is related to the AFM system.

Technical Service Bulletins (TSBs) & Recalls

• PIP4819A: Mentions inspecting and replacing loose spark plug wires for P030X codes.
• 15-06-01-002 (and its revisions A, B, C, H, L, M): Details diagnosis and repair for engine misfire/tick noise (P0300) caused by a mechanically collapsed or stuck AFM lifter due to oil aeration or internal damage.
• 19-NA-219: Diagnostic tip for various misfire codes (including P0306), listing potential causes like worn camshaft lobes, sticking valves, broken valve springs, and collapsed AFM lifters.

Platform-Specific Known Issues

• Active Fuel Management (AFM) Lifter Failure: This is the most significant vehicle-specific issue. The system deactivates cylinders 1, 4, 6, and 7. The lifters for these cylinders are prone to failure, causing them to collapse or stick. This results in a persistent misfire and a ticking noise from the engine. Repair is costly and involves significant labor.
• Loose Spark Plug Wires: Technical Service Bulletin #PIP4819A was issued by GM for misfire codes on these engines, explicitly stating that technicians should inspect for and replace any loose spark plug wires.

Mechanic-Grade Diagnostic Values

• Fuel Pressure (at fuel rail, Key On, Engine Off) — expected: 50-60 PSI. Failure: Pressure below 50 PSI can indicate a weak fuel pump or clogged filter, potentially causing lean misfires.
• Fuel Injector Resistance (Flex Fuel L94) — expected: 11-14 Ohms. Failure: A reading significantly outside this range, or an open/shorted circuit, indicates a failed injector coil.
• Ignition Coil Primary Resistance — expected: 0.3 - 1.0 Ohms. Failure: A reading outside this range suggests a faulty primary winding in the coil.
• Ignition Coil Secondary Resistance — expected: ~5.3k Ohms. Failure: A reading significantly different from this value suggests a faulty secondary winding.
• Engine Oil Pressure (Hot Idle) — expected: 25-30 PSI. Failure: Pressure significantly below this can starve the AFM lifters of oil, causing them to malfunction and trigger a misfire.

Hidden / Shadow Codes Worth Checking

• Mode 6, Test ID $A2-$A7: Mode 6 data tracks misfire counts for each cylinder (Cyl 1-6 are $A2-$A7, Cyl 7-8 are on a different Test ID). Even if the misfire count is not high enough to set a P0306 code and turn on the Check Engine Light, a technician can view these raw counts on a capable scanner to see if cylinder 6 is misfiring intermittently. (see via An OBD-II scanner with Mode 6 functionality.)

Scan Tool Commands That Help

• GM GDS2 / Tech2: Cylinder Deactivation Test (Cylinder Power Balance) — This function allows a technician to individually disable each cylinder one by one and observe the RPM drop. If disabling cylinder 6 causes little or no change in RPM compared to other cylinders, it confirms that cylinder 6 is not contributing power, pinpointing the misfire.
• GM GDS2 / Tech2: Injector Balance Test — This test pressurizes the fuel rail and then fires a single injector for a fixed duration, measuring the pressure drop. If the pressure drop for cylinder 6's injector is significantly different from the others, it indicates a clogged or faulty injector.
• GM GDS2 / Tech2: AFM Solenoid Control — When an AFM-related code like P3441 is present with P0306, this command allows the technician to manually command the cylinder 6 deactivation solenoid ON and OFF to check its electrical circuit and mechanical function.

Wiring & Ground Locations

• G102 — Located at the left rear of the engine.. This ground point is specifically for the 8 ignition coils. A loose or corroded connection here can cause a weak or intermittent spark on any or all cylinders, including cylinder 6.
• G104 — Located on the rear of the left (driver's side) cylinder head, connecting via a strap to the firewall.. This is a primary engine-to-chassis ground. A poor connection here can cause a wide range of electrical issues, including erratic sensor readings and ignition problems that could lead to a misfire.
• Cylinder 6 Injector Control Wire — This wire runs from the ECM to the fuel injector on cylinder 6.. A break, short-to-ground, or high resistance in this specific wire will prevent the fuel injector from firing correctly, directly causing a P0306 code. A wiring diagram is needed to trace the specific pin at the ECM.

Real Owner Repair Stories

• ScannerDanner Forum (2012 Cadillac Escalade 6.2L) — Misfire on cylinder 3 (P0303, but same diagnostic principle as P0306).
  ❌ Tried (didn't work) Swapped spark plug, Swapped ignition coil, Swapped spark plug wire, Checked for valve train movement (rockers moving okay), Verified injector pulse with a noid light
  ✅ What actually fixed it An injector balance test performed with a scan tool revealed the problem. While other cylinders showed a pressure drop from 70 PSI to 29 PSI during the test, the misfiring cylinder only dropped from 70 PSI to 47 PSI. This indicated the injector was partially clogged or faulty. Replacing the fuel injector resolved the misfire.

OEM Part Supersession History

• 12570616 → 12611424 (ACDelco D510C) — Standard part evolution and manufacturing updates.
  Heads up: The parts are considered directly interchangeable. Aftermarket listings often show that their coils replace both part numbers.
• Original AFM Lifter (e.g., Elgin HL-7011) → Newer DFM-compatible Lifter (e.g., Elgin HL-7025) — GM introduced a newer lifter design for Dynamic Fuel Management (DFM) engines starting in 2019. This new lifter is backward-compatible with older AFM systems.
  Heads up: The newer DFM lifter (HL-7025) can be used in older AFM engines, but the original AFM lifter (HL-7011) CANNOT be used in the newer DFM engines. For a 2010-2013 Escalade, either the direct AFM replacement or the newer backward-compatible DFM lifter can be used.

Model Year Variations Within This Range

• 2010-2013: The 2009 model year used the L9H engine, which had FlexFuel capability but did not have Active Fuel Management (AFM). For the 2010 model year, this was replaced by the L94 engine, which added AFM. Therefore, AFM-related causes for P0306 (like failed lifters or VLOM issues) apply specifically to the 2010-2013 model years of the Escalade EXT.
• 2010-2013: A known issue documented in TSB #PIP5161 involves a faulty PCV baffle in the driver's side valve cover that allows oil to be ingested into the intake, fouling spark plugs. While this TSB primarily points to misfires on cylinders 1 and 7, it represents a design issue present on these engines that could potentially affect other cylinders over time.