P0305 on 2010-2013 GMC Savana: Cylinder 5 Misfire Causes and Fixes

What's Unique About the 2010-2013 Gmc SAVANA

The GMC Savana is a workhorse van, often subjected to heavy loads and long idle times which can accelerate wear on ignition parts. For this specific platform, General Motors issued a Technical Service Bulletin (TSB #PIP4819A) that explicitly identifies loose spark plug wires as a known cause for misfire codes. Furthermore, the V8 engines in these vans (especially the 5.3L) can be prone to Active Fuel Management (AFM) lifter failure, which can present as a single-cylinder misfire like P0305 accompanied by a ticking sound.

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 engine idle.
• Engine stumbling or hesitating during acceleration, which can sometimes feel like a transmission issue.
• Flashing Check Engine Light, especially under load.
• Noticeable loss of engine power.
• Reduced fuel economy.
• A smell of raw fuel from the exhaust.
• A distinct ticking or tapping noise from the engine, which could indicate a serious lifter problem.

Most Likely Causes

1. Loose or Faulty Spark Plug Wire 🔴 High Probability → Shop Spark Plug A manufacturer TSB (#PIP4819A) was issued for this exact problem, stating that loose spark plug wires are a known cause of misfires on this platform. Owners report that aftermarket wires can sometimes be too long and rub against the steering shaft, eventually pulling the boot loose from the spark plug or coil.
   How to confirm: Visually inspect the wire for cylinder 5. Ensure it is securely clicked onto both the ignition coil and the spark plug. Check for any signs of corrosion, burns, or physical damage. Wiggle the wire to ensure it's not loose.
   Typical fix: Securely re-seat the wire. If damaged, replace the spark plug wire. It is best practice to replace all wires as a set with a quality brand like ACDelco to ensure proper fit.
   Est. part cost: $50-$100
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug
   How to confirm: Remove the spark plug from cylinder 5. Inspect it for wear on the electrode, carbon buildup, oil fouling, or cracks in the porcelain. A worn plug is a very common cause.
   Typical fix: Replace the spark plug. It is highly recommended to replace all spark plugs 🎬 See this walkthrough on how to replace your Savana's spark plugs. at the same time to ensure even performance. Use the correct OEM-spec Iridium plugs (ACDelco 41-162 or equivalent).
   Est. part cost: $40-$100
3. Faulty Ignition Coil 🟡 Medium Probability → Shop Ignition Coil
   How to confirm: Swap the ignition coil from cylinder 5 with an adjacent cylinder (e.g., cylinder 3). Clear the codes and drive the vehicle. If the code changes to P0303, the ignition coil is bad. Some owners report that replacing the plug and wire only temporarily fixes the issue, with the misfire returning, which often points to a weak coil.
   Typical fix: Replace the faulty ignition coil.
   Est. part cost: $30-$70
4. Clogged or Failing Fuel Injector ⚪ Low Probability → Shop Fuel Injector
   How to confirm: Listen to the injector with a mechanic's stethoscope or a long screwdriver. It should make a consistent, audible clicking sound. Compare its sound to the injectors on other cylinders. A 'noid light' can also be used to confirm the injector is receiving an electrical signal.
   Typical fix: Replace the faulty fuel injector. This is more involved than ignition parts.
   Est. part cost: $50-$120

Rare But Worth Checking

• Collapsed AFM/DOD Lifter: → Shop Engine Valve Lifter The Active Fuel Management (AFM) or Displacement on Demand (DOD) system lifters are a known failure point on GM V8s. A lifter can become stuck or collapse, preventing the valve from opening and causing a persistent misfire on one cylinder. This is often accompanied by a distinct ticking noise. If ignition and fuel checks do not solve the P0305, this is a strong possibility, especially if you hear ticking. 🎬 Watch this guide to diagnose lifter ticks versus other engine noises. This is a major, expensive repair that can also damage the camshaft. TSBs #15-06-01-002F and #19-NA-219 address this issue.
• Intake Manifold Gasket Leak: → Shop Engine Intake Manifold A vacuum leak from a failed intake manifold gasket near cylinder 5 can lean out the air/fuel mixture, causing a misfire. On Vortec engines, these leaks are common and may be more apparent when the engine is cold. A smoke test is the best way to diagnose this, but leaks can be on the underside of the manifold and hard to see. This often appears with lean codes P0171 or P0174.
• Low Engine Compression: Internal engine issues like a bad valve, worn piston rings, or a damaged piston can cause a loss of compression. This requires a mechanical compression test to confirm and is a serious repair.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0305 and check for any other codes.
2. Listen to the engine. Is there a loud, rhythmic ticking noise? If so, the probability of a mechanical lifter issue increases significantly.
3. Locate cylinder 5. On GM V8 engines, the cylinders on the driver's side are 1, 3, 5, and 7, from front to back. Cylinder 5 is the third cylinder back on the driver's side.
4. Inspect the spark plug wire for cylinder 5. Per TSB #PIP4819A, ensure it is fully seated on the coil and plug. Check for damage or rubbing against the steering shaft.
5. Swap the ignition coil from cylinder 5 with another cylinder (e.g., cylinder 3). Clear the codes, run the engine, and see if the misfire code moves to the new cylinder (P0303). If it does, the coil is bad.
6. If the code remains P0305, remove and inspect the spark plug. Look for wear, fouling, or damage. If it's in poor condition, replace it. It's best to replace all plugs as a set.
7. If ignition parts are good, check the fuel injector for cylinder 5. Listen for a steady clicking noise. A silent or inconsistent injector is likely faulty.
8. If the cause is still not found, perform a compression test to rule out mechanical engine problems like rings or valves.
9. If compression is good, check for vacuum leaks near the intake manifold for cylinder 5 using a smoke machine.

Parts You'll Likely Need

• Spark Plug Wire Set (OEM #9748UU) — A known failure point on this vehicle, as documented by a manufacturer TSB. Wires can become loose or fail, causing a misfire. OEM wires are recommended for proper fit.
  Trusted brands: ACDelco
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Iridium Spark Plug (OEM #41-162 or 19417055) — Spark plugs are a routine maintenance item and a primary cause of single-cylinder misfires as they wear out. The 41-162 is an updated part number for the original 41-110.
  Trusted brands: ACDelco, NGK
  OEM price range: $8-$15 per plug
  Aftermarket price range: $6-$12 per plug
• Ignition Coil (OEM #12611424) — The ignition coil provides the high voltage for the spark. While durable, they can fail over time, leading to a misfire that may be intermittent at first.
  Trusted brands: ACDelco, Delphi
  OEM price range: $45-$70
  Aftermarket price range: $30-$50

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or beginning to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may also be stored. This is common with lifter or intake gasket issues.
• P0171 or P0174 — If the misfire is caused by a vacuum leak from the intake manifold gasket, a 'System Too Lean' code for the corresponding engine bank may also appear.

Technical Service Bulletins (TSBs) & Recalls

• PIP4819A: Addresses engine misfires and directs technicians to inspect and replace loose spark plug wires.
• 19-NA-219: Discusses engine noises and misfires (P0300-P0308) and lists potential causes including worn camshaft lobes, sticking valves, and collapsed AFM lifters.
• 15-06-01-002F: Details engine misfire/tick noise with DTC P0300 caused by a mechanically collapsed or stuck AFM lifter.

Platform-Specific Known Issues

• A Technical Service Bulletin (TSB #PIP4819A) was issued for 2010-2013 GMC Savana models. It states that misfire codes (P0300-P0308) can be caused by loose spark plug wires and instructs technicians to inspect and replace them as needed.
• The 5.3L and other V8s in this van are known for failures of the Active Fuel Management (AFM) lifters. A collapsed lifter is a common cause of a single-cylinder misfire and is typically accompanied by a ticking noise. This is a much more severe and costly repair than standard ignition problems.
• The plastic intake manifolds combined with the gasket design on Vortec engines can lead to vacuum leaks as the vehicle ages, causing lean misfires that are sometimes hard to trace.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance — expected: 11.5 - 14.0 ohms. All injectors should be within 0.5 ohms of each other.. Failure: A reading outside the specified range, or one that deviates significantly from the other injectors, indicates a faulty injector.
• Ignition Coil Primary Resistance — expected: 0.4 - 0.6 ohms.. Failure: A reading outside this range suggests a faulty primary winding in the coil.
• Ignition Coil Secondary Resistance — expected: 5,000 - 10,000 ohms (5kΩ - 10kΩ). Some aftermarket coils may differ, e.g., 17kΩ.. Failure: An open circuit (infinite resistance) or a reading far outside the expected range indicates a failed secondary winding.
• Fuel Pressure (Key On, Engine Off) — expected: 55 - 62 PSI for the Multec 2 system used in this era.. Failure: Pressure significantly below this range indicates a weak fuel pump, clogged filter, or faulty regulator.

Hidden / Shadow Codes Worth Checking

• Misfire History Counters: Professional scan tools like the GM GDS2 can display current and historical misfire counts for each cylinder, even for misfires not severe enough to set a DTC. This is crucial for diagnosing intermittent issues. (see via Access the 'Misfire Data' or 'Engine Data' list on a GM-compatible professional scan tool (GDS2, Tech2, or high-end aftermarket).)

Scan Tool Commands That Help

• GDS2 / Professional Scan Tool: Cylinder Power Balance Test — Use this bidirectional control after basic ignition parts have been checked. The tool deactivates one fuel injector at a time and measures the corresponding drop in engine RPM. A cylinder with little to no RPM drop is not contributing power and is the source of the misfire. This helps differentiate between a fuel, spark, or compression issue on a specific cylinder.

Wiring & Ground Locations

• ECM Connector X2, Pin 18 — On the gray 80-pin connector (X2) for the E38 Engine Control Module (ECM), located in the engine bay.. This is the control circuit pin for the cylinder 5 fuel injector. A continuity test from this pin to the injector connector can identify a broken wire. The wire is typically Brown/White.
• G102 — On the left rear of the engine block or cylinder head.. This is a primary ground for the bank of ignition coils on the driver's side (cylinders 1, 3, 5, 7). A loose or corroded G102 can cause weak or intermittent spark for all four cylinders on that bank, leading to misfires.
• G103 — On the right front (passenger side) of the cylinder head.. This is another critical engine ground. While G102 grounds the coils, other grounds like G103 ensure the ECM and its sensors have a clean reference, preventing erratic behavior that could be misinterpreted as a misfire.

Real Owner Repair Stories

• YouTube channel 'How to Fix P0305 Misfire (Cylinder 5) | GMC & Chevy 5.3L / 6.2L' (2014 Chevrolet Silverado 5.3L (similar GMT platform and engine)) — Stuttering/hesitation during acceleration, flashing check engine light, P0305 code stored.
  ❌ Tried (didn't work) Replacing the spark plug and spark plug wire for cylinder 5 only made the symptoms go away temporarily. The misfire returned later the same day without setting a code initially.
  ✅ What actually fixed it Replacing the ignition coil for cylinder 5 resolved the issue permanently. The video also notes that aftermarket plug wires can be too long and rub on the steering shaft, causing a loose connection, which is a common issue to check.

OEM Part Supersession History

• ACDelco 41-110 → ACDelco 41-162 — Supplier change (from Denso to NGK, or vice-versa) and a slight design change. The 41-162 is physically shorter.
  Heads up: While both are specified for these engines, some users report better idle quality with the older 41-110 plugs if they can be found. Always verify the correct part for your specific VIN.
• Multiple older AFM lifter part numbers (e.g., 12571595, 12632143) → 12680871, 12698946 — Re-engineered to address the high failure rate of the original AFM lifters. GM also released an updated Valve Lifter Oil Manifold (VLOM), part #12571609, to improve oil delivery to the lifters.
  Heads up: When replacing failed AFM lifters, it is highly recommended to also replace the VLOM with the updated design to prevent repeat failures.

Model Year Variations Within This Range

• 2010-2013: Ignition coils on these engines can come in two physical styles: a 'square' body (e.g., ACDelco D514A) or a 'round' body (e.g., ACDelco D510C). It is critical to visually inspect the existing coils before ordering replacements to ensure the correct style is purchased.