P0302 on 2010-2013 GMC Savana: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2010-2013 Gmc SAVANA

GMC Savana vans from this era are workhorses, often equipped with robust Vortec V8 engines (4.8L, 5.3L, or 6.0L). A key documented issue for these vehicles is the failure of spark plug wires due to heat and age, as highlighted in General Motors Technical Service Bulletin (TSB) #PIP4819A. The constant high heat in the engine bay, combined with the tight access of the 'doghouse' engine cover, makes ignition components a frequent failure point. Additionally, some V8 engines are equipped with Active Fuel Management (AFM), which has a known failure point in the valve lifters that can cause persistent misfires.

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 shaky idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Flashing or solid Check Engine Light
• Reduced fuel economy
• Potential fuel smell from the exhaust
• Engine ticking or chirping noise, especially if related to a lifter issue

Most Likely Causes

1. Faulty Spark Plug Wire 🔴 High Probability → Shop Spark Plug A manufacturer TSB (#PIP4819A) specifically calls out inspecting and replacing loose or faulty spark plug wires for this code on these vehicles. The insulation can break down from engine heat over time, causing the spark to arc to ground. The boot can also develop small holes, causing a spark leak.
   How to confirm: Visually inspect the wire for cylinder 2 for any cracks, burns, or corrosion. Ensure it is seated firmly. At night, you can sometimes see the spark arcing from the wire to a metal part of the engine. A user on a forum noted finding a burned-through hole in the wire boot.
   Typical fix: Replace the entire set of spark plug wires. It is best practice to replace them all at once. 🎬 Watch: Full walkthrough for replacing plugs, wires, and coils.
   Est. part cost: $40-$90
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a standard maintenance item. On Vortec engines, oil consumption can sometimes lead to premature fouling of the plugs. Using the incorrect plug type can also lead to issues.
   How to confirm: Remove the spark plug from cylinder 2 and inspect it. Look for a worn electrode, incorrect gap, cracked porcelain, or heavy carbon/oil deposits.
   Typical fix: Replace the spark plug. It is highly recommended to replace all 8 spark plugs at the same time with the correct OEM-spec iridium plugs.
   Est. part cost: $40-$100
3. Bad Ignition Coil 🟡 Medium Probability → Shop Ignition Coil The coil-on-plug design exposes the coils to significant heat, which can cause them to fail over time. This is a very common failure point across all GM trucks and vans with this engine family.
   How to confirm: Swap the ignition coil from cylinder 2 with another cylinder (e.g., cylinder 4). Clear the codes and drive the vehicle. If the code changes to P0304, the ignition coil is faulty. This is a widely accepted diagnostic step in owner forums.
   Typical fix: Replace the faulty ignition coil.
   Est. part cost: $30-$70
4. Clogged or Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector Fuel injectors can become clogged with deposits over time, preventing the correct amount of fuel from reaching the cylinder. While less common than ignition issues, it's a known cause. One owner on a GMTNation forum tried fuel injector cleaner as a first step for a P0302, though it didn't solve their specific issue.
   How to confirm: This is more difficult to diagnose. A professional can perform a fuel injector balance test. A DIY method is to listen to the injector with a mechanic's stethoscope to check for a consistent clicking sound. Swapping the injector from cylinder 2 with another cylinder is possible but labor-intensive.
   Typical fix: Clean or replace the faulty fuel injector.
   Est. part cost: $50-$150

Rare But Worth Checking

• Intake Manifold Gasket Leak: → Shop Engine Intake Manifold The intake manifold gaskets on these GM V8s are a known failure point. A leak near the cylinder 2 runner can cause a lean misfire by allowing unmetered air into the engine. This often presents with a P0171 or P0174 code as well and can sometimes cause a hissing noise.
• Low Engine Compression (AFM Lifter Failure): A mechanical issue like a worn piston ring, a bad valve, or a failing lifter can cause a persistent misfire. On engines with Active Fuel Management (AFM), a collapsed lifter is a well-documented problem that can cause a single-cylinder misfire. TSB #15-06-01-002F addresses this issue, which often starts with a ticking noise and a P0300, but can isolate to one cylinder. This failure can lead to camshaft damage if not addressed.
🎬 Watch: How AFM lifter failure causes these misfire codes.

Diagnosis Steps

1. Read the code with an OBD-II scanner and confirm P0302 is present. 🎬 See this guide on diagnosing a cylinder 2 misfire. Note if the Check Engine Light is flashing, which indicates a severe misfire.
2. Locate cylinder 2 (front cylinder on the passenger side for V8s).
3. Visually inspect the spark plug wire for cylinder 2 for any damage, cracks, or burns. Ensure it is seated firmly on the coil and plug.
4. Swap the ignition coil from cylinder 2 with the coil from cylinder 4. Clear the codes and run the engine to see if the misfire code moves to P0304. If it does, the coil is bad. This is a standard, effective DIY test.
5. If the misfire remains on cylinder 2, remove the spark plug. Inspect it for wear, fouling, or damage. Replace if necessary. It's best to replace all plugs and the wires at the same time.
6. If ignition components are good, listen to the fuel injector on cylinder 2 with a stethoscope for a steady clicking sound. Compare it to an adjacent injector.
7. If all ignition and fuel components for cylinder 2 are confirmed to be good, perform a compression test on cylinder 2 to check for mechanical engine problems like a bad valve or a collapsed AFM lifter.

Parts You'll Likely Need

• Spark Plug Wire Set (OEM #9748GG) — This is a primary failure point identified in a manufacturer TSB and is a common wear item under the high-heat conditions of the Savana's engine bay. Note: Other similar ACDelco part numbers exist like 9748RR or 9748UU for different model year ranges or specific applications, always verify fitment.
  Trusted brands: ACDelco, NGK, Delphi
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Iridium Spark Plugs (OEM #41-110 or 41-162) — Spark plugs are a routine maintenance item and a frequent cause of single-cylinder misfires. The 41-110 was superseded by the 41-162, though some users report better performance with the older 41-110 spec. Always confirm the correct plug for your specific VIN.
  Trusted brands: ACDelco, NGK
  OEM price range: $8-$15 per plug
  Aftermarket price range: $6-$12 per plug
• Ignition Coil (OEM #12713668) — While less common than plugs or wires, an individual coil can fail and is easy to diagnose by swapping its position.
  Trusted brands: ACDelco, Delphi
  OEM price range: $45-$70
  Aftermarket price range: $30-$50
• Fuel Injector (OEM #12613412) — If ignition parts don't solve the misfire, a clogged or failed fuel injector is the next most likely fuel system cause.
  Trusted brands: ACDelco, Bosch
  OEM price range: $80-$150
  Aftermarket price range: $50-$100

Related Codes That Often Appear With This One

• P0300 — If the condition causing the misfire in cylinder 2 is also starting to affect other cylinders, or if the root cause is a major mechanical issue like a failing AFM lifter, a P0300 (Random/Multiple Cylinder Misfire) code may also be present.
• P0304, P0306, P0308 — If the cause is common to one bank of cylinders (like a clogged catalytic converter or a bad ground for the coils on the passenger side), you may see misfire codes for other cylinders on that same bank (2, 4, 6, 8).
• P0171, P0174 — If the misfire is caused by a vacuum leak, such as a faulty intake manifold gasket, the engine may run lean, triggering a 'System Too Lean' code for one or both banks.

Technical Service Bulletins (TSBs) & Recalls

• PIP4819A: Addresses engine misfires (P0300-P0308) and advises inspection and replacement of loose spark plug wires.
• 15-06-01-002F: Details diagnosis for engine misfire/tick noise (P0300) caused by a mechanically collapsed or stuck Active Fuel Management (AFM) lifter, a potential root cause for a persistent P0302.

Platform-Specific Known Issues

• A known TSB (#PIP4819A) points directly to loose or faulty spark plug wires as a cause for P030x misfire codes on this platform.
• Vortec V8 engines with Active Fuel Management (AFM) are prone to lifter failure, which can manifest as a persistent P0302 code and may require significant mechanical repair. TSB #15-06-01-002F discusses this issue.

Mechanic-Grade Diagnostic Values

• Fuel Pressure (Key On, Engine Off) — expected: 50 to 62 PSI. Failure: Pressure below 50 PSI indicates a weak fuel pump or leak. Pressure that bleeds off quickly after the pump primes indicates a bad check valve or leak.
• Ignition Coil Primary Resistance — expected: 0.4 to 2.0 ohms. Failure: A reading of 0 ohms indicates a short, while an infinite (O.L.) reading indicates an open circuit.
• Ignition Coil Secondary Resistance — expected: 6,000 to 10,000 ohms (6k-10k Ω). Failure: Readings significantly outside this range suggest a faulty coil winding.
• Scan Tool Misfire Counter (Mode 6) — expected: Near zero for all cylinders on a healthy engine.. Failure: A rapidly increasing count for cylinder 2 confirms the misfire is actively occurring. Comparing the count to other cylinders helps gauge severity.

Scan Tool Commands That Help

• GDS2 / Tech2 or equivalent professional scan tool: Cylinder Power Balance Test — This is a crucial diagnostic step when the cause of the misfire isn't obvious. The tool deactivates one cylinder at a time (by cutting fuel or spark) and measures the corresponding drop in RPM. If deactivating cylinder 2 causes little or no RPM drop compared to other cylinders, it confirms that cylinder 2 was not contributing power, isolating the fault.
• GDS2 / Tech2 or equivalent professional scan tool: Fuel Injector Balance Test — If an ignition problem has been ruled out, this test can confirm or deny a fuel injector issue. The tool commands each injector to fire for a specific duration, and the resulting drop in fuel pressure is measured. An inconsistent pressure drop for cylinder 2 points to a faulty injector.

Wiring & Ground Locations

• G103 — On the right rear of the engine block (passenger side).. This is a primary engine-to-chassis ground. A loose or corroded G103 can cause erratic behavior and weak spark for the entire passenger-side bank of cylinders (2, 4, 6, 8), leading to misfires.
• G104 — On the left rear corner of the engine, often where a ground strap connects the cylinder head to the firewall.. While on the driver's side, this ground is critical for the overall engine management system. A poor connection here can cause issues for the ECM, which controls spark and fuel for all cylinders.
• Ignition Coil Connector (Cylinder 2) — The electrical connector on the ignition coil for cylinder 2 (front-most coil on the passenger side).. This is where voltage and control signals are delivered to the coil. Technicians test for battery voltage on the pink wire (Key On) and check the control signal from the ECM on the other wire using a noid light or oscilloscope during cranking.

Real Owner Repair Stories

• Mighty Auto Parts technical article (General GM V8 with Active Fuel Management (AFM), applicable to 2010-2013 Savana) — Chirping, ticking, or squeaking noise, Check Engine Light, and engine misfire codes (such as P0302).
  ❌ Tried (didn't work) Initial diagnostics that did not include mechanical inspection.
  ✅ What actually fixed it The root cause was a collapsed or stuck AFM lifter, which resulted in low compression on that cylinder. The fix required visual inspection of the camshaft and lifters, and replacement of the damaged components. In some cases, the camshaft lobe was also worn and required replacement.

OEM Part Supersession History

• ACDelco 41-985 → ACDelco 41-110, then ACDelco 41-162 — Design changes and/or change in manufacturer (e.g., from NGK to Denso or vice-versa).
  Heads up: While all are generally compatible, the 41-162 is physically shorter than the 41-110. Some owners and mechanics express a preference for the build quality of the older 41-110 plugs, claiming they provide a smoother idle, though the 41-162 is the official GM replacement.