P0277 on 2010-2014 GMC Terrain V6: Cylinder 6 Injector Circuit Low Causes & Fixes

What's Unique About the 2010-2014 Gmc TERRAIN

The GMC Terrain and its platform-mate, the Chevrolet Equinox, are specifically called out in General Motors TSB #PIP4924D for issues with the fuel injector wiring harness. The harness is routed tightly and is prone to rubbing against engine components like the back of the intake plenum, sharp edges on valve cover bolts, or nearby fuel lines, leading to chafed or broken wires. This makes a wiring fault a much higher probability on this platform compared to a random fuel injector failure, a fact corroborated by numerous owner experiences in online forums.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light is on
• Rough or unstable idle
• Engine misfire, which may feel like a stumble or hesitation
• Reduced engine power and poor acceleration
• Decreased fuel economy
• A raw fuel smell from the exhaust

Most Likely Causes

1. Chafed or Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As documented in GM TSB #PIP4924D, the V6 engine's injector harness is known to rub against the intake plenum, valve cover bolts, or fuel lines, causing wires to chafe or break. This is the most common failure point for this specific code on this platform.
   How to confirm: Visually inspect the entire length of the wiring harness leading to the cylinder #6 fuel injector. Pay close attention to any points of contact with other engine parts, especially on the back side of the engine near the intake and on the side of the cylinder head under the plenum. Check for continuity on the injector circuit wires using a multimeter. A 'wiggle test' on the harness while monitoring the multimeter can help find intermittent breaks. 🎬 Watch: This video shows how to find a hidden broken wire.
   Typical fix: Repair the damaged section of wire using a solder and heat-shrink butt connector. If the damage is near the connector, a new pigtail connector (such as Dorman 645-595 or an equivalent ACDelco pigtail) may need to be spliced in. Secure the harness away from sharp edges or hot components with zip ties or conduit to prevent recurrence.
   Est. part cost: $10-$40
2. Faulty Cylinder 6 Fuel Injector 🟡 Medium Probability → Shop Fuel Injector While wiring is more common, the direct injectors used in the 3.0L and 3.6L V6 engines can fail electrically or become clogged over time.
   How to confirm: After confirming the wiring is intact, test the injector. Use a multimeter to check the injector's internal resistance; it should be within the manufacturer's specification (typically 1.5-2.5 ohms for these GDI engines). You can also swap the cylinder 6 injector with another one (e.g., from cylinder 4) and see if the trouble code follows the injector to the new cylinder (e.g., becomes P0271). This is labor-intensive as it requires removing the intake manifold.
   Typical fix: Replace the faulty fuel injector. It is often recommended to replace all injectors on the same bank (or all six) if they are high mileage, as others may fail soon.
   Est. part cost: $50-$140
3. Loose or Corroded Electrical Connector ⚪ Low Probability
   How to confirm: Unplug and inspect the connector at the fuel injector and the corresponding pins at the ECM. Look for any signs of corrosion, moisture, or bent/loose pins. Ensure the connector clicks securely into place.
   Typical fix: Clean the connector terminals with an electrical contact cleaner. Apply a small amount of dielectric grease to the seal before reconnecting. If pins are damaged, the connector pigtail will need to be replaced.
   Est. part cost: $0-$30

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is the least likely cause. The ECM's internal driver for the injector circuit can fail, but all other possibilities, especially wiring and the injector itself, must be exhaustively ruled out before condemning the ECM.
• Cylinder Block Porosity: A rare but documented issue in some GM V6 engines involves coolant leaking into the cylinder due to porosity in the engine block casting. This can cause misfires, especially when cold, and may set various DTCs. This is a catastrophic failure requiring engine replacement and is not a primary cause of a P0277 electrical code, but can be a related underlying issue in severe cases.

Diagnosis Steps

1. Verify the code P0277 is present using an OBD-II scanner.
2. Identify cylinder #6. On the transverse V6, it is located on the bank closest to the radiator, on the driver's side.
3. Carefully and thoroughly inspect the fuel injector wiring harness for cylinder #6, as recommended by TSB #PIP4924D. Look for chafing against the intake plenum, valve cover bolts, fuel lines, and the side of the cylinder head. This may require removing the engine cover and using a mirror and flashlight.
4. Inspect the electrical connector at the cylinder 6 injector for damage, corrosion, or loose pins.
5. If no visible damage is found, disconnect the injector and use a multimeter to measure its resistance. It should be between 1.5 and 2.5 ohms. Compare the reading to a known-good injector on the same engine.
6. Use a noid light at the injector connector to verify that the ECM is sending a pulse signal. If the noid light flashes, the ECM and wiring are likely okay, pointing towards a bad injector.
7. If the noid light does not flash, check for continuity and shorts to ground on both wires between the injector connector and the ECM. Wiggle the harness during this test to expose any intermittent faults.
8. If wiring and the injector test good, the final and least likely possibility is a faulty injector driver in the ECM.

Parts You'll Likely Need

• Fuel Injector (OEM #12634126) — If the injector's internal coil has failed, it will need to be replaced. This is a common failure point after the wiring has been ruled out. This part number is for the 3.6L LFX V6 (2013-2014). The 3.0L V6 (2010-2012) uses a different part, such as 12638530.
  Trusted brands: ACDelco, Hitachi
  OEM price range: $110-$140
  Aftermarket price range: $50-$80
• Fuel Injector Connector Pigtail (OEM #ACDelco PT2160 (verify connector style)) — If the wiring harness is damaged right at the connector, splicing in a new pigtail is the standard repair. The connector must match the injector. The connector style is typically USCAR EV6.
  Trusted brands: Dorman (e.g., 645-595), ACDelco
  OEM price range: $25-$45
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0306 — P0306 means 'Cylinder 6 Misfire Detected.' Since P0277 indicates an electrical fault that prevents the injector from firing correctly, the cylinder will not have proper combustion, directly causing a misfire.
• P2149 — This code relates to 'Fuel Injector Group B Supply Voltage Circuit/Open.' The V6 engines in these vehicles group injectors into banks. A wiring issue that causes P0277 might also affect the shared power or ground circuit for that entire bank of injectors (cylinders 2, 4, and 6).
• P0276 — This is the corresponding 'low circuit' code for cylinder 5. If the harness chafing affects multiple wires, it's possible to see codes for adjacent or nearby injector circuits.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Addresses a Check Engine Light and misfire with various injector codes, including P0277, caused by the fuel injector wiring harness rubbing through or having internal wire opens. This TSB applies to a wide range of GM vehicles with the 3.0L and 3.6L V6 engines.

Platform-Specific Known Issues

• A General Motors Technical Service Bulletin (PIP4924D) was issued for a range of vehicles including the 2010-2014 Terrain with V6 engines, specifically citing injector codes like P0277. The bulletin directs technicians to inspect the fuel injector wiring harness for rubbing through or internal wire opens, particularly against the intake plenum, at valve cover bolts, against the fuel line and on the side of the head under the plenum.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance (V6 GDI Engines) — expected: 1.5 - 2.5 Ohms. Failure: A reading of infinity (OL) indicates an open coil; a reading near zero indicates a shorted coil. The most important check is comparing the resistance to other injectors on the same engine.
• Injector Power Wire Voltage (Key On, Engine Off) — expected: ~12 Volts (Battery Voltage). Failure: Voltage significantly below battery voltage points to high resistance in the power supply circuit or a blown fuse.
• Injector Balance Test Pressure Drop Variance — expected: All injectors should have a pressure drop within 1.5 PSI (or 20 kPa) of each other.. Failure: An injector with a pressure drop significantly different from the others is likely clogged or malfunctioning.

Scan Tool Commands That Help

• GDS2 / Tech2: Injector Balance Test — Use this bidirectional test after confirming the wiring is intact. The tool commands each injector to fire for a set duration and measures the corresponding drop in fuel rail pressure. It's a highly effective way to identify a mechanically failing or clogged injector without having to physically remove it.

Wiring & Ground Locations

• G113 — On the left side of the engine block (reported for 3.0L V6 models).. A poor or corroded main engine ground can cause a variety of erratic electrical issues and incorrect voltage readings, including injector circuit faults. Ensuring this ground is clean, tight, and has low resistance is a crucial step in any electrical diagnosis.
• ECM Connectors (X1, X2, X3) — At the Engine Control Module (ECM), typically located in the engine bay.. Service diagrams label the large ECM connectors as X1, X2, etc. For the LFX V6, X1 is often the blue connector. Knowing which connector houses the injector circuit pins is essential for performing continuity and voltage tests directly at the ECM.

OEM Part Supersession History

• 12638530 → 12669384 (unconfirmed for Terrain, but cited for LLT engine) — Part update/revision.
  Heads up: Part number 12638530 is cited for the 3.0L LF1 V6 engine used in 2010-2012 models. It is NOT compatible with the 3.6L LFX engine.
• 12642128 → 12634126 — Part update/revision.
  Heads up: Part number 12634126 is cited for the 3.6L LFX V6 engine used in 2013-2014 models. It is NOT compatible with the 3.0L LF1 engine.

Model Year Variations Within This Range

• 2010-2012 vs 2013-2014: The primary V6 engine changed between these periods. 2010-2012 models used the 3.0L V6 (LF1), while 2013-2014 models received the 3.6L V6 (LFX). While they share the same TSB regarding wiring harness chafing, the fuel injectors are different and are not interchangeable. Always verify the correct part number by VIN, as using an injector for the wrong engine will result in performance issues, even if it physically fits.