P0307 on 2010-2013 Cadillac CTS-V: Cylinder 7 Misfire Causes and Fixes

What's Unique About the 2010-2013 Cadillac CTS

This guide is exclusively for the high-performance CTS-V model, which uses the 6.2L LSA supercharged V8 engine; standard V6 CTS models do not have spark plug wires and cannot generate this specific code in the same way. The LSA engine generates significant heat, especially at the rear of the engine bay where cylinder 7 is located (rear-most cylinder on the driver's side). This heat puts extra stress on ignition components. A General Motors TSB #PIP4819A specifically points to loose spark plug wires as a known cause for misfires on these engines, making it a unique and highly probable first point of inspection.

Diagnostic Flowchart

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

Symptoms You May Notice

• Flashing or solid Check Engine Light
• Rough idle or engine shaking
• Hesitation or stumbling during acceleration
• Noticeable loss of power
🎬 Watch: Understanding the symptoms and fixes for a P0307 code.
• Increased fuel consumption
• Exhaust may smell like gasoline
• Engine vibration felt through the steering wheel

Most Likely Causes

1. Loose or Faulty Spark Plug Wire 🔴 High Probability → Shop Spark Plug GM Technical Service Bulletin #PIP4819A directly identifies loose spark plug wires as a cause for misfires (including P0307) on 2010 models. The high-heat environment of the supercharged V8, particularly around cylinder 7 at the back of the engine, can degrade wire insulation and boots over time, leading to a poor connection or arcing.
   How to confirm: Locate cylinder 7 (rear-most on the driver's side). Check if the spark plug wire is securely clicked onto the ignition coil and the spark plug. Wiggle the boot to check for looseness. A proper connection will often produce an audible 'click'. Inspect the wire for any signs of burns, cracks, corrosion, or melting, especially where it may be close to the exhaust manifold.
   Typical fix: Reseat the wire firmly. Applying a small amount of dielectric grease to the inside of the boot can help with sealing and future removal. If the connection is loose or the wire is damaged, replace the entire set of spark plug wires to ensure uniform resistance and performance.
   Est. part cost: $70-$150
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are regular maintenance items. The high cylinder pressures and heat of a supercharged engine can shorten their effective lifespan. The recommended OEM plug is often an ACDelco Iridium type.
   How to confirm: Remove the spark plug from cylinder 7. Inspect it for wear on the electrode, carbon fouling, oil, or signs of damage. A good diagnostic step is to swap the cylinder 7 plug with one from another cylinder (e.g., cylinder 1), clear the codes, and see if the misfire moves to P0301.
   Typical fix: Replace the spark plug. The OEM recommended part is an ACDelco Iridium plug (e.g., 41-162). It is best practice to replace all 8 spark plugs at the same time for consistent performance. Note that Iridium plugs are pre-gapped and should not be adjusted. 🎬 Watch: A step-by-step walkthrough for changing plugs on an LSA engine.
   Est. part cost: $12-$25 per plug
3. Faulty Ignition Coil 🟡 Medium Probability → Shop Ignition Coil Heat and vibration are primary causes of ignition coil failure. The coil for cylinder 7 is located in a high-heat area at the rear of the engine.
   How to confirm: Swap the ignition coil from cylinder 7 with another cylinder (e.g., cylinder 1). Clear the codes and drive the vehicle. If the code changes to P0301, the ignition coil is faulty.
   Typical fix: Replace the faulty ignition coil. The OEM part is typically ACDelco P/N 12619161.
   Est. part cost: $40-$90
4. Clogged or Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector Fuel injectors can become clogged over time with fuel deposits, although it's less common than ignition issues for a single-cylinder misfire. Use of fuels with high ethanol content may contribute to injector issues.
   How to confirm: This is more difficult to confirm without specialized tools. A professional can perform a fuel injector balance test. A DIY method is to listen for the injector's clicking sound with a mechanic's stethoscope. Swapping injectors is possible but more labor-intensive than swapping coils or plugs.
   Typical fix: Clean or replace the faulty fuel injector.
   Est. part cost: $70-$150

Rare But Worth Checking

• Low Cylinder Compression (Broken Valve Spring): A broken valve spring can cause an intermittent or consistent misfire and may be accompanied by a ticking noise. This is a known, though less common, issue on GM V8 engines. If ignition and fuel causes are ruled out, a compression test is necessary. A reading 20% lower than other cylinders indicates a mechanical problem. This is an unlikely cause on a well-maintained engine but should be checked if all other causes are ruled out.
• Worn Supercharger Isolator: The factory LSA supercharger snout contains a spring-loaded isolator that can wear out, causing a rattling or clanking sound at idle, sometimes described as 'marbles in a can'. While this doesn't typically cause a single-cylinder misfire directly, the associated vibrations and harmonics can sometimes be misinterpreted by the PCM or contribute to other issues. The fix is to replace the spring-loaded unit with a solid isolator.
• Damaged Fuel Injector Wiring: → Shop Fuel Injector The wiring harness or connector for the fuel injector can become damaged from heat and vibration, causing an intermittent connection that mimics a faulty injector. A 'wiggle test' on the connector while the engine is running can sometimes reveal a bad connection if the misfire changes.

Diagnosis Steps

1. Read the code with an OBD-II scanner and confirm P0307 is present. Note any other codes.
2. Locate cylinder 7, which is the rearmost cylinder on the driver's side of the engine.
3. Per TSB #PIP4819A, first inspect the spark plug wire for cylinder 7. Ensure it is fully seated on both the ignition coil and the spark plug with an audible 'click'. Inspect for damage, melting, or arcing.
4. If the wire is secure and appears undamaged, swap the ignition coil from cylinder 7 with the coil from cylinder 1. Clear the codes and drive the vehicle to see if the misfire code changes to P0301. If it does, the coil is bad.
🎬 See this guide on troubleshooting LS engine misfires to save money.
5. If the misfire remains on cylinder 7, swap the spark plug from cylinder 7 with the plug from cylinder 1. Clear codes and drive. If the code changes to P0301, the spark plug is bad.
6. If the misfire still remains on cylinder 7, inspect the wiring and connector to the fuel injector for cylinder 7 for any damage or looseness. Perform a 'wiggle test' on the wiring with the engine running to see if it affects the idle.
7. If the above steps do not isolate the issue, the problem may be with the fuel injector or a mechanical engine problem.
8. Listen to the fuel injector with a mechanic's stethoscope to confirm it is clicking like the others.
9. If all else fails, perform a cylinder compression test to check for mechanical engine issues like a broken valve spring or poor valve seating.

Parts You'll Likely Need

• Spark Plug Wire Set (OEM #ACDelco 9748UU) — This is the most likely cause according to GM TSB #PIP4819A. Wires should be replaced as a set to ensure uniform resistance and performance. Heat degradation is common.
  Trusted brands: ACDelco, NGK
  OEM price range: $90-$120
  Aftermarket price range: $70-$100
• Spark Plug (OEM #ACDelco 41-162) — A common wear item and a frequent cause of single-cylinder misfires. The LSA engine requires high-quality iridium plugs for longevity and performance.
  Trusted brands: ACDelco (OE), NGK
  OEM price range: $15-$25
  Aftermarket price range: $10-$18
• Ignition Coil (OEM #12619161) — A common point of failure for ignition systems, easily diagnosed by swapping its position. Heat is a primary factor in failure.
  Trusted brands: ACDelco, Delphi
  OEM price range: $60-$90
  Aftermarket price range: $40-$70

Related Codes That Often Appear With This One

• P0300 — If the cause of the misfire (like a vacuum leak or low fuel pressure) becomes more severe, it can start to affect other cylinders, leading to a P0300 (Random/Multiple Cylinder Misfire) code in addition to the P0307.

Technical Service Bulletins (TSBs) & Recalls

• PIP4819A: Malfunction Indicator Lamp and the engine misfires... Technician may find Diagnostic Trouble Codes P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, and P0308. Technician will need to inspect the spark plug wires. Technician will need to replace any loose spark plug wires.
• 19-NA-219: A more general GM bulletin discussing various causes for misfire codes (P0300-P0308), including worn cam lobes, sticking valves, and broken valve springs, which can be relevant if common ignition fixes fail.

Platform-Specific Known Issues

• Technical Service Bulletin #PIP4819A was issued by GM for engine misfires, including P0307, on 2010 models. The bulletin instructs technicians to inspect for and replace any loose spark plug wires.
• The location of cylinder #7 at the rear driver's side of the engine bay is a hot spot, making the spark plug wire and coil in that position more susceptible to heat-related failure than other cylinders.
• Owners on forums frequently report that the #7 spark plug wire boot can come loose or fail to 'click' into place securely, causing an intermittent connection and misfire.