P0306 on 2007-2009 Saturn Aura 3.6L: Cylinder 6 Misfire Causes and Fixes

What's Unique About the 2007-2009 Saturn Aura

While a P0306 is often a simple ignition issue, the Saturn Aura's 3.6L LY7 V6 engine has a well-documented, widespread history of premature timing chain stretching. This serious mechanical issue can cause misfires, often starting on one cylinder before progressing to random misfires (P0300) and setting specific timing codes (like P0008, P0017). The issue was so prevalent that GM issued multiple Technical Service Bulletins (e.g., #12-06-01-009F) and a Special Coverage Adjustment (#11340C) for many affected vehicles, acknowledging the problem was often caused by the original chain design and an overly optimistic Oil Life Monitor (OLM) calibration that led to oil degradation. Therefore, while a bad coil or plug is the most probable cause for an isolated P0306, the possibility of it being an early symptom of timing chain failure cannot be ignored on this specific engine.

Symptoms You May Notice

• Check Engine Light is on or flashing
• Rough or vibrating engine idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Reduced fuel economy
• Strong smell of raw fuel from the exhaust
• Engine may make popping or backfiring sounds.

Most Likely Causes

1. Failed Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are subject to high heat and vibration. The front bank of coils on the transverse V6, which includes cylinder 6, is relatively easy to access, but constant heat cycles cause eventual failure.
   How to confirm: Swap the ignition coil from cylinder 6 with another cylinder on the same bank (e.g., cylinder 4). Clear the codes and drive the vehicle. If the code changes to P0304, the ignition coil is faulty.
   Typical fix: Replace the failed ignition coil. It is often recommended to replace all coils on the same bank, or all six, if they are original and high-mileage. Always apply dielectric grease to the inside of the new coil boot to prevent moisture intrusion and ease future removal.
   Est. part cost: $30-$70 per coil
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a standard wear item. Additionally, the LY7 engine can be prone to valve cover gasket leaks, which allow oil to seep into the spark plug tubes, fouling the plug and causing a misfire. A Reddit user with an '08 Aura 3.6L specifically noted finding oil in a spark plug tube while chasing a misfire.
   How to confirm: After confirming the coil is good, remove the spark plug from cylinder 6. Inspect it for wear (worn electrode), carbon fouling, oil saturation, or cracks in the porcelain. The correct spark plug gap for the 3.6L LY7 is approximately 0.043 inches.
   Typical fix: Replace the spark plug. It is best practice to replace all six spark plugs at the same time to maintain consistent performance. Use OEM-specification Iridium plugs for longevity. If oil is present, the valve cover gasket and spark plug tube seals should be replaced. 🎬 See how to install new spark plug tube seals properly.
   Est. part cost: $10-$25 per plug
3. Stretched Timing Chains 🟡 Medium Probability The 3.6L LY7 V6 is notorious for premature timing chain wear. This was caused by a combination of the original chain design and an overly optimistic Oil Life Monitor (OLM) calibration that led to oil degradation. A stretched chain can cause camshaft timing to be out of sync, leading to misfires. Owners on CarComplaints.com report failures as early as 56,000-60,000 miles.
   How to confirm: This is a more advanced diagnosis. Look for accompanying codes like P0008, P0016, or P0017. A professional technician can use a scan tool to monitor camshaft deviation angles to confirm timing has slipped. The presence of these codes alongside a P0306 is a strong indicator of this issue.
   Typical fix: This is a major and expensive repair that involves replacing all three timing chains, tensioners, and guides with updated parts. GM released updated kits to address the problem (TSB #12-06-01-009F). 🎬 Watch: Expert tips and tricks for GM 3.6L timing chain replacement. The water pump is often replaced at the same time due to its location.
   Est. part cost: $400-$800 for a complete kit
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector
   How to confirm: If the misfire remains on cylinder 6 after swapping the coil and plug, the injector is a suspect. A technician can test the injector's electronic pulse or perform a flow test. A simpler DIY method is to listen to the injector with a mechanic's stethoscope to hear if it's clicking. Swapping the injector with another cylinder is the most definitive DIY test, but requires removing the fuel rail.
   Typical fix: Replace the faulty fuel injector. It's recommended to replace the O-rings on adjacent injectors when the fuel rail is removed.
   Est. part cost: $50-$150

Rare But Worth Checking

• Low Engine Compression: If ignition and fuel systems check out, a mechanical engine problem could be the cause. A compression test on cylinder 6 can check for issues like a worn piston ring, a burnt valve, or a leaking head gasket. Overheating events on the aluminum LY7 engine can lead to warped cylinder heads, causing compression loss.
• Intake Manifold Gasket Leak: → Shop Engine Intake Manifold A vacuum leak near the cylinder 6 intake runner can lean out the air/fuel mixture and cause a misfire. A smoke test is the most effective way to diagnose a vacuum leak. The plastic intake manifold itself can also crack, causing a similar leak.

Diagnosis Steps

1. Confirm the P0306 code using an OBD-II scanner and check for any other stored codes. Note any pending or historic codes.
2. Identify Cylinder 6. On the transverse 3.6L V6 in the Saturn Aura, the engine bank closer to the radiator is Bank 2. The cylinders on this bank are 2, 4, and 6, arranged from the passenger side (right) to the driver's side (left). Cylinder 6 is the front-most cylinder on the driver's side.
3. Swap the ignition coil from cylinder 6 with an easier-to-access cylinder on the same bank, such as cylinder 4. Clear the codes and run the engine to see if the misfire moves.
4. Rescan for codes. If code P0304 appears, the ignition coil is bad and needs replacement.
5. If the code remains P0306, swap the spark plug from cylinder 6 with cylinder 4. Clear codes and run the engine.
6. Rescan for codes. If code P0304 appears, the spark plug is the culprit.
7. If the P0306 code persists, inspect the wiring and connector for the ignition coil and fuel injector on cylinder 6 for any damage, corrosion, or loose connections.
8. Consider a faulty fuel injector. This can be confirmed by swapping the injector with another cylinder, but this is a more involved job.
9. If all else fails, perform a compression test on cylinder 6 to rule out mechanical engine damage like worn rings or a bad valve.
10. If timing-related codes like P0008 or P0017 are present, suspect a stretched timing chain and seek professional diagnosis immediately.

Parts You'll Likely Need

• Ignition Coil (OEM #12632479) — This is the most common failure part for a single-cylinder misfire. Heat and vibration cause the internal windings to fail over time.
  Trusted brands: ACDelco (OEM), Delphi, NGK, Denso, Duralast
  OEM price range: $50-$80
  Aftermarket price range: $30-$60
• Iridium Spark Plug (OEM #41-107) — Spark plugs are a regular maintenance item that wear out, causing a weak spark. Oil fouling from leaky gaskets can also ruin a plug.
  Trusted brands: ACDelco (OEM), NGK, Bosch
  OEM price range: $15-$25
  Aftermarket price range: $10-$20

Related Codes That Often Appear With This One

• P0300 — If the underlying issue, like a vacuum leak or failing timing chain, begins to affect other cylinders, a P0300 (Random/Multiple Misfire) code may appear.
• P0008 / P0017 — These codes indicate a camshaft/crankshaft correlation error. On the 3.6L LY7 engine, their presence alongside a misfire code is a very strong indicator of stretched timing chains.
• P0430 — This code indicates 'Catalyst System Efficiency Below Threshold (Bank 2)'. A persistent misfire on cylinder 6 (which is in Bank 2) will dump unburned fuel into the exhaust, damaging the Bank 2 catalytic converter and triggering this code.

Technical Service Bulletins (TSBs) & Recalls

• 12-06-01-009F: Announces the availability of updated timing chain kits for repairing stretched timing chains that cause misfires and timing codes.
• 11340C: A Special Coverage Adjustment that extended the warranty for timing chain wear on many GM vehicles with the LY7 engine, though it has now expired for all 2007-2009 models.
• TSB Bulletin #PIP5038B: Notes that vehicles may have a Service Engine Soon lamp on with codes including P0300 through P0306, as well as ignition coil circuit codes P0351 through P0356, requiring technicians to follow published Service Information diagnostics.

Platform-Specific Known Issues

• The 3.6L LY7 V6 engine is widely known for premature timing chain stretching, which can manifest as a single or multiple-cylinder misfire. GM issued TSB #12-06-01-009F regarding updated timing chain kits and Special Coverage Adjustment #11340C (now expired) which extended the warranty to 10 years/120,000 miles due to the high failure rate.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance — expected: 11.0 - 14.0 Ohms. Failure: A reading of 0 Ohms (short), infinite/OL (open), or significantly outside the specified range indicates a faulty injector coil.
• Fuel Injector Circuit Voltage (Key On, Engine Off) — expected: ~12V (Battery Voltage) on the power feed wire at the injector connector.. Failure: Low or no voltage points to a problem in the power supply circuit, such as a blown fuse or wiring damage.
• Fuel Pressure (Key On, Engine Off) — expected: 48 - 65 PSI. Failure: Pressure below 41 PSI suggests a weak fuel pump or clogged filter, which could cause a lean misfire.
• Mass Airflow (MAF) Sensor at Idle (Warmed Up) — expected: 3.6 to 4.8 g/s. Failure: Readings outside this range at idle can indicate unmetered air (vacuum leak) or a faulty sensor, affecting the air/fuel mixture for all cylinders.

Scan Tool Commands That Help

• GM Tech 2 / GDS2: Cylinder Power Balance Test — This function allows the technician to sequentially disable one cylinder at a time and observe the drop in RPM. If disabling cylinder 6 causes little or no change in RPM compared to other cylinders, it confirms that cylinder 6 is not contributing power, verifying the misfire.
• GM Tech 2 / GDS2: Fuel Injector Balance Test — After ruling out ignition issues, this test can identify a clogged or failing fuel injector. It measures the pressure drop as each injector is fired, and a significant deviation on cylinder 6 would indicate a fueling problem.

Wiring & Ground Locations

• G105 — Center rear of the engine block for the 3.6L LY7.. This is a primary engine ground. A poor connection here can cause erratic behavior in various engine sensors and actuators, including the ignition system.
• G111 — Top rear right side of the engine on the 3.6L LY7.. Another critical engine ground. A loose or corroded G111 can lead to intermittent and hard-to-diagnose electrical issues, potentially including misfires.
• G113 — On the center of the left side cylinder head for the 3.6L LY7.. This ground is specific to the cylinder head and can affect components grounded to it. Verifying its integrity is important when chasing electrical faults on that bank.
• ECM (Engine Control Module) — On the left (front) side of the engine compartment, in front of the battery for the 3.6L models.. The ECM controls both the ignition coil and fuel injector for cylinder 6. Knowing its location is essential for any circuit testing that traces back to the computer, such as checking for signal voltage or continuity on the control wires.

OEM Part Supersession History

• 12590990, 12610626, 12618542 → 12632479 — Internal design and material improvements by GM to increase durability and resistance to heat-related failure.
• 12650231 (for 2008-2009 models) → 12651420 (part of newer kits) — Updated timing chain design to address premature stretching. The new chains are more robust. Aftermarket kits from Cloyes (e.g., 9-0753S) or Melling are also considered durable replacements.
  Heads up: Always use a complete kit with matched chains, guides, and tensioners. Do not mix old and new design components.
• 12650230 (for 2007 models) → 12651420 (part of newer kits) — Updated timing chain design to address premature stretching.
  Heads up: The 2007 model year used a slightly different initial kit than 2008-2009, but modern replacement kits cover all years. Verify application before purchase.

Model Year Variations Within This Range

• 2007 vs 2008-2009: The original equipment timing chain kits specified by GM differed between the 2007 model (PN 12650230) and the 2008-2009 models (PN 12650231). While both suffered from premature wear and have been superseded by newer, more durable designs, this indicates a minor component change early in production.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• 6T70 Transmission 3-5-R Wave Plate Failure 🔴 High — Very common, typically occurs between 70,000 and 120,000 miles. Leads to loss of 3rd, 5th, and Reverse gears. (Ref: GM Special Coverage #14404B extended the warranty to 10 years/120,000 miles for this specific failure.)
• Premature Timing Chain Stretch 🔴 High — Widespread issue on the LY7 V6, often appearing from 60,000 miles onward. Caused by chain design and long oil change intervals. (Ref: TSB #12-06-01-009F, Special Coverage Adjustments #10287, #11340C.)
• Loss of Electric Power Steering (EPS) Assist 🔴 High — Common enough to warrant a recall. Can result in a sudden increase in steering effort, especially at low speeds. (Ref: GM Recall #14V153000 (GM recall number 14118).)
• Leaking Valve Cover Gaskets / Spark Plug Tube Seals 🟠 Medium → Shop Spark Plug — A common source of oil leaks that can lead to spark plug fouling and ignition coil failure.
• Failed Intermediate Steering Shaft 🟠 Medium — Can cause a clunking or popping noise in the steering column when turning. A recall was issued for some replacement parts. (Ref: Recall for certain Dorman replacement parts, but the issue is common with OEM shafts as well.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used OEM ignition coil from a low-mileage donor vehicle can be a cost-effective and reliable alternative to a new, unproven aftermarket coil. Since coils don't have mechanical wear parts, a used OEM unit is often superior to a cheap new one. Other simple mechanical components like brackets or connectors are also good candidates for used parts.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For an ignition coil, check for cracks in the plastic housing and ensure the boot is pliable and not brittle.
• Look for a vehicle that appears well-maintained and is free of front-end collision damage.
• Ask the salvage yard for the mileage of the donor vehicle if possible; lower is always better.
• Inspect wiring connectors for corrosion, brittleness, or cut wires.

OEM-only on this vehicle (don't cheap out):

• Timing Chain Kit: This is a high-labor, critical repair. Do not use used parts. While OEM is an option, premium aftermarket brands like Cloyes or Melling are widely considered to be equal or superior to the original GM parts for this specific issue.

Aftermarket brands forum-validated for this vehicle:

• Ignition Coils: ACDelco (OEM), NGK, Denso, Delphi.
• Spark Plugs: ACDelco (OEM), NGK.
• Timing Chain Kits: Cloyes, Melling.

Brands owners have reported issues with on this vehicle:

• Unbranded or 'white-box' ignition coils and sensors from online marketplaces. While tempting due to low cost, they have a high failure rate and can cause persistent diagnostic headaches.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0304 — A misfire code for cylinder 4; often appears during diagnosis when swapping coils or plugs from cylinder 6 to verify a component failure.
• P0008 — Engine positions system performance code; frequently accompanies P0306 when the root cause is a stretched timing chain on the LY7 engine.
• P0016 — Crankshaft Position - Camshaft Position Correlation code; a common companion to misfire codes indicating the timing chain has stretched and cam timing is out of sync.
• P0017 — Crankshaft Position - Camshaft Position Correlation (Bank 2) code; specifically relates to the bank containing cylinder 6 and indicates timing chain wear.

Frequently Asked Questions