P0276 on 2009-2014 Buick Enclave: Cylinder 6 Injector Circuit Low Causes & Fixes

What's Unique About the 2009-2014 Buick ENCLAVE

The 2009-2014 Buick Enclave, along with its GM Lambda platform mates (like the Acadia, Traverse, and Outlook) equipped with the 3.6L V6 engine, is specifically called out in Technical Service Bulletin (TSB) #PIP4924D for this family of codes. The TSB highlights that the fuel injector wiring harness is prone to rubbing through or developing internal opens. Specific chafe points mentioned are against the intake plenum, at valve cover bolts, against the fuel line, and on the side of the cylinder head under the plenum. This makes a wiring inspection a critical first step, often before suspecting the injector itself.

Diagnostic Flowchart

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Symptoms You May Notice

• Check Engine Light is on or flashing
• Rough or shaky engine idle
• Reduced engine power and poor acceleration
• Engine hesitation or stumbling
• Noticeable drop in fuel economy
• Smell of raw fuel from the exhaust
• Engine vibration, especially at idle

Most Likely Causes

1. Damaged Fuel Injector Wiring Harness 🔴 High Probability As documented in GM TSB #PIP4924D, the harness on the 3.6L V6 engine is known to rub against engine components. Specific chafe points to check are against the intake plenum, valve cover bolts, the fuel line, and the side of the cylinder head under the plenum.
   How to confirm: Carefully inspect the entire fuel injector harness, especially the sections running along the back of the intake manifold and near the cylinder heads. Look for any signs of rubbing, exposed wires, or pinching. Another TSB, #21-NA-149, shows examples of harness chafing on the front corner of the left cylinder head and near the PVC hose clamp.
   Typical fix: Repair the damaged section of the wire following proper soldering and heat-shrinking procedures. Reroute the harness slightly or add protective conduit (harness sleeves, anti-abrasion tape) to prevent future rubbing.
   Est. part cost: $5-$50 for wiring repair supplies
2. Failed Cylinder 6 Fuel Injector 🟡 Medium Probability The direct fuel injector itself can fail internally, causing an electrical short that results in a 'circuit low' condition.
   How to confirm: After confirming the wiring is intact, test the injector. You can measure its resistance with a multimeter. A healthy GM 3.6L direct injector should have a resistance of approximately 1.2-1.8 ohms for the LFX engine or 1.5-2.2 ohms for the LLT. A reading that is significantly lower than spec indicates a shorted injector. Alternatively, swap the cylinder 6 injector with another cylinder's injector (e.g., cylinder 4). If the code follows the injector (e.g., changes to P0270), the injector is bad.
   Typical fix: Replace the faulty fuel injector. It is often recommended to replace all injectors on that bank or the entire set if the vehicle has high mileage, as accessing them requires removing the intake manifold.
   Est. part cost: $70-$280 for a single injector
3. Poor Connection at Injector or ECM ⚪ Low Probability Vibration and heat can cause connectors to become loose or corroded over time. The connector pin itself can be damaged from moisture or road salt.
   How to confirm: Disconnect and inspect the electrical connector at the cylinder 6 fuel injector and the corresponding pins at the ECM. Look for bent, corroded, or loose-fitting pins.
   Typical fix: Clean the connector pins with electrical contact cleaner or replace the connector pigtail if it's damaged.
   Est. part cost: $15-$40 for a new connector pigtail

Rare But Worth Checking

• Faulty Engine Control Module (ECM): This is the least likely cause. The internal driver circuit for the cylinder 6 injector within the ECM can fail. This should only be considered after all wiring and the injector itself have been proven to be good.

Diagnosis Steps

1. Read all fault codes using an OBD-II scanner. Note P0276 and any other codes like P0306.
2. Perform a thorough visual inspection of the fuel injector wiring harness, paying close attention to the areas mentioned in TSB #PIP4924D: against the intake plenum, at valve cover bolts, against the fuel line, and on the side of the cylinder head.
3. Inspect the electrical connector at the cylinder 6 fuel injector for damage, corrosion, or a loose fit.
4. Use a noid light to test for a signal at the cylinder 6 injector connector. A flashing light indicates the ECM is trying to fire the injector.
5. If the signal is good, turn off the ignition and disconnect the injector. Measure the injector's internal resistance with a multimeter. A healthy LFX injector should read approximately 1.2-1.8 ohms, while an LLT injector should be 1.5-2.2 ohms. Compare the reading to a known-good injector on the engine. A reading that is significantly lower than spec indicates a shorted injector.
6. If the resistance is out of spec, the injector is faulty and needs replacement.
7. If the wiring and injector test good, the final possibility is a fault within the ECM's injector driver circuit, though this is rare.

Parts You'll Likely Need

• Fuel Injector (OEM #12663380 (LFX), 12638530 (LLT)) — This is the second most common cause after a wiring issue. The injector can short internally. Note: Part number varies by engine. 2009-2011 models with the LLT engine typically use 12638530. 2012-2014 models with the LFX engine use 12663380, which supersedes 12634491.
  Trusted brands: ACDelco, GM Genuine Parts, Bosch, Standard Motor Products
  OEM price range: $145-$280
  Aftermarket price range: $70-$150
• Upper and Lower Intake Manifold Gaskets — To access the fuel injectors on the 3.6L V6, the upper intake manifold must be removed. The gaskets are single-use and must be replaced to prevent vacuum leaks. This is shown in repair videos for the platform.
  Trusted brands: ACDelco, Fel-Pro, Mahle
  OEM price range: $40-$80
  Aftermarket price range: $20-$50
• Fuel Injector Connector Pigtail (OEM #e.g., Standard Motor Products S-1024) — If the connector itself is found to be corroded or damaged, replacing the pigtail is the proper repair.
  Trusted brands: ACDelco, Dorman, Standard Motor Products
  OEM price range: $25-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0306 — This code means 'Cylinder 6 Misfire Detected'. It is a direct symptom of the P0276 fault, as the injector circuit problem prevents proper fueling, causing the cylinder to misfire.
• P0201-P0205, P0261, etc. — If the wiring harness is chafing, it can damage multiple injector circuits at once, causing several injector codes to appear simultaneously. The provided TSB #PIP4924D lists a large family of these codes.
• P0300 — This 'Random/Multiple Cylinder Misfire' code can be triggered if the wiring issue affects more than one injector or if the engine is running very poorly due to the cylinder 6 problem.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Addresses potential rub-through or internal damage to the fuel injector wiring harness, causing various injector circuit codes including P0276. Recommends careful inspection of the harness against the intake, valve covers, and fuel lines. This TSB applies to a wide range of GM vehicles using the 3.6L V6 engine.

Platform-Specific Known Issues

• A known issue documented in TSB #PIP4924D involves the fuel injector wiring harness rubbing through against various engine components, leading to shorts or open circuits. This is a primary suspect for code P0276 on this platform.
• Owner forums and repair videos show that accessing the fuel injectors requires the removal of the upper intake manifold, making the repair labor-intensive for a DIYer and adding several hours of labor at a shop.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance (2012-2014 LFX Engine) — expected: 1.2 - 1.8 Ohms. Failure: A reading of 0 ohms (short), OL/infinity (open), or significantly outside this range indicates a failed injector coil.
• Fuel Injector Coil Resistance (2009-2011 LLT Engine) — expected: 1.5 - 2.2 Ohms. Failure: A reading significantly lower than 1.5 ohms indicates a shorted injector; an infinite reading (OL) indicates an open circuit.
• Low-Pressure Fuel System Pressure (Key On, Engine Off) — expected: 345-690 kPa (50-100 psi). Failure: Pressure below the specified range indicates a weak in-tank fuel pump or a restriction in the fuel line.
• High-Pressure Fuel System Pressure (at idle) — expected: 350-500 PSI. Failure: Low high-side pressure would typically set other codes like P0087, but confirms the overall health of the GDI system.
• Injector Pulse Width (at idle, warm engine) — expected: Approximately 1-5 milliseconds. Failure: A pulse width of 0 ms for cylinder 6 confirms the ECM is not commanding the injector due to the circuit fault.
• Injector Circuit Wiring Resistance to Ground — expected: Infinite resistance (Open Line/OL). Failure: Any continuity or low resistance reading indicates a short to ground in the control wire, a common cause for a 'Circuit Low' code.

Scan Tool Commands That Help

• GDS2 (GM Dealer Tool) or high-end aftermarket scanner: Automated Fuel Injector Balance Test — This is a key diagnostic step for GDI engines. The tool commands each injector to fire and measures the corresponding drop in fuel rail pressure. A cylinder with a pressure drop that deviates significantly (e.g., more than 20 kPa or 3 psi) from the average indicates a faulty injector. This helps differentiate a bad injector from a wiring problem after the wiring has been inspected.
• GDS2 (GM Dealer Tool): Injector Kill / Cylinder Power Balance — While the engine is running, a technician can use the scan tool to disable one injector at a time. When a good cylinder is disabled, the engine RPM will drop. If disabling cylinder 6 causes no change in how the engine runs, it confirms that cylinder is not contributing, which is expected with a P0276 code.

Wiring & Ground Locations

• Engine Grounds (General) — On the 3.6L V6, there are typically three smaller ground connections on the engine block itself, often on the rear or corner of the cylinder heads, and one large ground cable from the battery that bolts to the engine block, sometimes near the starter.. A poor engine ground can cause a variety of unpredictable electrical faults and voltage drops. While not a direct cause of a single injector circuit code, verifying the main engine grounds are clean and tight is a crucial step in any electrical diagnosis.
• Cylinder 6 Injector Control Wire — This wire runs from a specific pin on the Engine Control Module (ECM) connector to the fuel injector connector for cylinder 6. Cylinder 6 is on the front bank (near the radiator), on the driver's side.. This is the wire that the ECM pulses with a ground signal to fire the injector. A 'Circuit Low' code is most often caused by this specific wire shorting to ground somewhere along its path, frequently due to the harness chafing documented in TSB #PIP4924D.

OEM Part Supersession History

• 12638530 → 12669384 — Standard part update/revision by the manufacturer.
  Heads up: This part is for the LLT engine only and is not compatible with the 2012+ LFX engine.
• 12634491 → 12663380 — Standard part update/revision by the manufacturer.
  Heads up: This part is for the LFX engine only and is not compatible with the pre-2012 LLT engine.

Model Year Variations Within This Range

• 2009-2011: These models use the 3.6L LLT V6 engine, which has an aluminum intake manifold, non-integrated exhaust manifolds, and uses a Bosch ECM. The specified fuel injector is typically part number 12638530.
• 2012-2014: These models use the updated 3.6L LFX V6 engine. This engine features a composite intake manifold, exhaust manifolds that are integrated into the cylinder heads, and uses a Delphi ECM. The specified fuel injector is part number 12663380. Due to these changes, parts like injectors, intake gaskets, and the ECM are not interchangeable with the earlier LLT models.