P0277 on 2012-2014 Chevrolet Impala: Cylinder 6 Injector Circuit Causes and Fixes

What's Unique About the 2012-2014 Chevrolet IMPALA

The 3.6L LFX V6 engine, used across many GM vehicles including the Impala, has a well-documented issue with its fuel injector wiring harness. The harness routing makes it prone to rubbing against engine components like the intake plenum, valve cover bolts, or the sharp edge of the cylinder head. This chafing eventually wears through the wire's insulation, causing a short circuit that triggers code P0277. This is so common that GM issued a Technical Service Bulletin (TSB #PIP4924D) to guide technicians in diagnosing this exact problem. Cylinder 6 is on the rear bank (Bank 2), making visual inspection and access more difficult than for the front cylinders.

Diagnostic Flowchart

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

Generation note: The 2012-2014 year range includes the end of the ninth generation (2012-2013, and 2014 'Limited' models) and the start of the tenth generation (2014). Both generations used the 3.6L LFX V6 engine, and this issue applies to both as confirmed by TSB PIP4924D which covers these model years.

Symptoms You May Notice

• Check Engine Light is on
• Engine running rough or vibrating, especially at idle
• Noticeable engine misfire or stumble
• Hesitation or lack of power during acceleration
• Reduced fuel economy
• Strong fuel smell from the exhaust

Most Likely Causes

1. Chafed/Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As documented in GM TSB #PIP4924D, the wiring harness is known to rub against the intake plenum, valve cover bolts, fuel lines, or the cylinder head, causing a short. Forum users and mechanics frequently find the damage on the firewall side of the engine (Bank 2), where the harness may be secured too tightly against a metal bracket or the edge of the head.
   How to confirm: Visually inspect the entire fuel injector harness for Bank 2 (cylinders 2, 4, 6). Pay close attention to where the harness bends around the back of the cylinder head and where it's secured by clips or zip ties. Look for worn plastic conduit, shiny/melted spots on wires, or exposed copper. A wiggle test on the harness while the engine is idling may induce a misfire, confirming an intermittent connection.
   Typical fix: Repair the damaged section of wire using a solder splice and heat-shrink tubing. Protect the repaired area and the rest of the harness with new plastic split-loom tubing. Secure the harness away from any sharp metal edges to prevent a recurrence. If damage is at the connector, a new pigtail can be spliced in.
   Est. part cost: $10-$110
2. Failed Cylinder 6 Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Direct injection injectors operate under very high pressure and can fail electrically over time. However, on this platform, it is less common than the wiring issue.
   How to confirm: After confirming the wiring is intact, swap the cylinder 6 fuel injector with an injector from another cylinder (e.g., cylinder 4). Clear the codes and drive. If the code changes to P0275 (Cylinder 4 Injector Circuit), the injector is faulty. A multimeter can also be used to check the injector's resistance; a reading outside the manufacturer's specification (typically 1.2-1.8 ohms for the LFX direct injection engine) indicates failure.
   Typical fix: Replace the failed fuel injector. It is often recommended to replace all injectors on that bank (Bank 2), or all six, if they are original, due to the labor involved in accessing them which requires removing the upper intake manifold. 🎬 Watch: Full walkthrough of intake removal and injector replacement.
   Est. part cost: $75-$150
3. Faulty Engine Control Module (ECM) ⚪ Low Probability → Shop Engine Control Module (ECM)
   How to confirm: This should only be considered after the wiring and injector have been definitively ruled out. A professional shop would use advanced tools to test the injector driver circuit within the ECM. An absence of a pulsed ground signal at the injector connector (using a noid light or oscilloscope) when the wiring is known to be good points to the ECM.
   Typical fix: Replace and reprogram the ECM.
   Est. part cost: $300-$600

Rare But Worth Checking

• Bent or Damaged Pins at the ECM Connector: A visual inspection of the ECM harness connector is quick and can rule out a simple physical connection issue before condemning an expensive computer.
• Corroded or Loose Injector Connector: Moisture or vibration can lead to a poor connection directly at the cylinder 6 injector. Unplug the connector and inspect for any green/white corrosion or loose-fitting pins.

Diagnosis Steps

1. Scan for Codes: Confirm P0277 and note any other codes, 🎬 Watch: Understanding the P0277 code and what it means. especially P0306 or P0206.
2. Inspect the Wiring Harness: This is the most critical step. Carefully inspect the fuel injector wiring harness for Bank 2 (rear bank) for any signs of rubbing (chafing). Per TSB #PIP4924D, focus on where it passes over the valve cover, near the intake plenum, against fuel lines, and against the sharp edges of the cylinder head. A user on AcadiaForum.net found wires for cylinders 4 and 6 chafed through where they were zip-tied to a metal bracket on the firewall side.
3. Test the Injector Signal: Use a 'noid light' to test the electrical signal at the cylinder 6 injector connector. The light should flash steadily while the engine is cranking or running. If the light is dim, off, or stays on solid, it confirms a wiring or ECM issue.
4. Check for Shorts: If the wiring looks damaged, disconnect the harness from the ECM and the injector. Use a multimeter set to Ohms to check for continuity to ground on the injector control wire. If continuity exists (low resistance), you have confirmed a short circuit.
5. Swap the Injector: If the wiring appears to be in perfect condition, swap the cylinder 6 injector with one from another cylinder on the same bank (e.g., cylinder 4). Clear the codes and run the engine. If the code returns as P0275 (for cylinder 4), the injector itself is faulty. If P0277 returns, the problem is in the wiring or the ECM.
6. Test the ECM: If both the wiring and injector are confirmed to be good, the final step is to have the ECM's injector driver circuit tested by a professional, as this is the least likely point of failure.

Parts You'll Likely Need

• Fuel Injector Wiring Harness (OEM #12690531) — This is the most common failure point due to the known chafing issue described in TSB #PIP4924D. This part number corresponds to the Bank 2 (Left Hand/Driver Side) harness for the transverse LFX engine.
  Trusted brands: GM Genuine
  OEM price range: $100-$160
• Fuel Injector (OEM #12638530) — If the wiring is intact, the injector itself may have failed electrically.
  Trusted brands: ACDelco (217-3445), Bosch, Hitachi
  OEM price range: $85-$140
  Aftermarket price range: $75-$115
• Split Loom Tubing — Essential for protecting a repaired wire or the entire harness from future chafing damage.
  Trusted brands: Dorman, Generic
  Aftermarket price range: $5-$15

Related Codes That Often Appear With This One

• P0306 — P0306 means 'Cylinder 6 Misfire Detected.' Since P0277 indicates a fuel delivery problem for cylinder 6, a misfire is the direct result.
• P0206 — P0206 is a more general 'Cylinder 6 Injector Circuit/Open' code. A chafed wire can intermittently short (P0277) or break contact (P0206), sometimes causing both codes to be stored. Both are listed in TSB PIP4924D.
• P2155 — P2155 is 'Fuel Injector Group D Circuit Low/Open'. This indicates an issue with the circuit controlling Bank 2 (cylinders 2, 4, 6). A significant short in the cylinder 6 wiring can sometimes affect the entire bank and trigger this group code.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: SES Light And Misfire With Injector Codes... inspect the fuel injector wiring harness for rub through or internal wire opens. Common spots are against the intake plenum, at valve cover bolts, against the fuel line and on the side of the head under the plenum.

Platform-Specific Known Issues

• GM Technical Service Bulletin #PIP4924D (and its earlier versions) was issued for a wide range of GM vehicles with the 3.6L V6 engine, including the 2012-2013 Impala. It specifically addresses a list of fuel injector codes, including P0277, caused by the fuel injector wiring harness rubbing through against engine components.
• The location of Cylinder 6 on the rear bank (Bank 2, firewall side) makes accessing the injector and its wiring more labor-intensive than for cylinders on the front bank.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance (3.6L LFX V6) — 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.
• Injector Pulse Width (at idle on a scan tool) — expected: 2 - 4 milliseconds (ms). Failure: A value of 0 ms on cylinder 6 while other cylinders show normal pulsing indicates the ECM has likely disabled the injector due to the detected fault.
• Injector Circuit Voltage (Key On, Engine Off) — expected: Battery Voltage (approx. 12V) on the power feed wire. Failure: No voltage or low voltage suggests a problem in the power supply to the injector, not the control circuit.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Fuel Injector Balance Test — This is a definitive bidirectional test to confirm a faulty injector after the wiring has been verified as good. The tool commands each injector to fire and measures the drop in fuel rail pressure. If the pressure drop for cylinder 6 is significantly different (GM specifies variance >20%) from the average of the others, the injector is faulty.
• GDS2 / High-End Bidirectional Scanner: Injector Cut-Out / Disable — While the engine is idling, the technician can command the cylinder 6 injector to turn off. If the engine's idle quality does not change, it confirms that cylinder was not contributing (misfiring), pointing to a problem in that circuit. If the idle gets worse, the injector was working to some degree.
• GDS2 / High-End Bidirectional Scanner: KOEO Injector Electrical Self Test (Buzz Test) — This Key On, Engine Off test commands the ECM to cycle all injectors. The technician listens for an audible 'buzz' from each injector. A silent cylinder 6 injector would immediately point to an electrical issue in its circuit (wiring or injector coil) and can be performed before more invasive testing.

Wiring & Ground Locations

• G104 — On the rear of the driver's side (Bank 2) cylinder head.. This is a primary engine ground for Bank 2. While not a common cause for a single injector code, a loose or corroded G104 can cause a host of intermittent and difficult-to-diagnose electrical problems for all components on that cylinder bank, including the injectors. It's a quick check to ensure the ground path for the ECM and sensors is solid.
• Cylinder 6 Injector Wires — Within the Bank 2 fuel injector harness, running to the rearmost injector on the firewall side.. The control wire (low-side driver) is a solid color, while the power feed wire (high-side driver) is the same color with a white tracer. For example, if the control wire is solid dark green, the power wire will be dark green with a white stripe. Identifying these is critical for testing continuity and shorts between the injector connector and the ECM.
• ECM Connector X1 — The Engine Control Module (ECM) is located in the engine bay, often near the firewall or airbox. The injector wiring runs to the X1 connector.. Testing for continuity and shorts requires checking the specific pins for the cylinder 6 injector at this connector. A wiring diagram is needed to identify the exact pin numbers for the control and power wires for cylinder 6.

Real Owner Repair Stories

• Traverse Forum user (2011 Chevrolet Traverse 3.6L (mechanically similar engine and platform)) — Check Engine Light with codes P0273 (Cyl 5 Injector Circuit Low) and P0305 (Cyl 5 Misfire).
  ❌ Tried (didn't work) Initially suspected the fuel injector itself.
  ✅ What actually fixed it Upon inspection, the owner found the wiring harness had chafed through on the back of the cylinder head near the firewall. The wires for the injector were shorting to ground. Repairing the damaged wires and protecting the harness with a new loom resolved both codes, confirming the TSB-documented failure mode.
• Acadia Forum user (2012 GMC Acadia 3.6L (mechanically similar engine and platform)) — Engine running rough, especially at idle. Code P0270 (Cylinder 4 Injector Circuit Low).
  ❌ Tried (didn't work) Replacing the spark plug and ignition coil for the affected cylinder., Replacing the fuel injector for the affected cylinder.
  ✅ What actually fixed it After replacing parts did not work, a closer inspection of the fuel injector wiring harness revealed a wire had chafed through its insulation where it was secured by a zip tie to a metal bracket. The wire would short to ground intermittently with engine vibration. Repairing the wire and protecting the harness resolved the code.

OEM Part Supersession History

• 12632255 → 12638530 — Standard part evolution/update.
• 12638530 → 12669384 — Standard part evolution/update. The ACDelco equivalent for 12638530 is 217-3445.
  Heads up: While these parts are often listed as interchangeable for the LFX engine, it is critical to verify the correct part number for the specific vehicle's VIN, as subtle changes in injector design occurred.

Model Year Variations Within This Range

• 2012-2016: The 3.6L LFX direct-injected V6, used from 2012 onwards, features a Delphi ECM and direct-injection fuel injectors with a low coil resistance of around 1.2-1.8 Ohms. Earlier 3.6L (LLT) engines used a different ECM and port injectors with a much higher resistance (approx. 12 Ohms). Parts and diagnostic values are not interchangeable between LFX and LLT engines.