P0277 on 2010-2014 Cadillac SRX: Cylinder 6 Injector Circuit High Causes and Fixes

What's Unique About the 2010-2014 Cadillac SRX

For this generation of Cadillac SRX and other GM vehicles with the 3.0L or 3.6L V6 engines, a known weak point is the fuel injector wiring harness. GM issued multiple Technical Service Bulletins (TSBs), including the well-known #PIP4924D, that directly link injector codes like P0277 to the harness rubbing through its insulation at several common points in the engine bay. One particularly noted chafe point on similar platforms is where the harness passes the metal ECM bracket. This makes a wiring inspection a more critical first step on these vehicles than on others where the injector itself might be the primary suspect.

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 (Malfunction Indicator Lamp) is on
• Rough or unstable idle
• Engine misfire, which may feel like a stumble or shake
• Hesitation or poor acceleration
• Reduced engine power
• Increased fuel consumption
• Strong fuel smell from the exhaust

Most Likely Causes

1. Chafed or Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As identified in GM TSB #PIP4924D and others, the harness routing can lead to it rubbing against engine components. Common chafe points are against the intake plenum, valve cover bolts, fuel lines, the side of the cylinder head, and the metal ECM bracket. Engine vibration causes the wire's insulation to wear through, creating a short to voltage or an open circuit.
   How to confirm: Visually inspect the entire length of the fuel injector harness leading to cylinder 6. On the transverse-mounted V6 in the SRX, cylinder 6 is on the front bank (closest to the radiator), on the driver's side. Peel back the plastic loom and look for bare copper wires, melted plastic, or areas where the harness has rubbed through. Pay special attention to where the harness bends near brackets or touches the engine.
   Typical fix: Repair the damaged section of wire with a quality solder connection and heat shrink tubing. If the damage is extensive or at the connector, a harness pigtail may be required. Secure the repaired harness away from the chafe point using anti-abrasion tape and zip ties to prevent recurrence.
   Est. part cost: $5-$25 for repair materials, $50-$100 for a harness pigtail or section.
2. Faulty Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Direct injection injectors operate under high pressure and can fail internally over time, leading to electrical faults like shorts or opens in the internal coil.
   How to confirm: Swap the cylinder 6 fuel injector with an adjacent one (e.g., cylinder 4). Clear the codes and drive the vehicle. If the code changes to P0271 (Cylinder 4 Injector Circuit High), the injector is faulty. Alternatively, measure the injector's resistance with a multimeter. For the 3.6L LFX engine, a good injector should measure between 1.2 and 1.8 Ohms. For the 3.0L LF1 (a high-impedance injector), expect around 12 Ohms. A reading far outside this range indicates a bad injector.
   Typical fix: Replace the faulty fuel injector. It is often recommended to replace all injectors on the same bank or all six at once for balanced performance, especially on higher mileage vehicles.
   Est. part cost: $60-$190 per injector.
3. Poor Connection at Injector or ECM ⚪ Low Probability
   How to confirm: Disconnect the connectors at the cylinder 6 fuel injector and the ECM. Inspect for corrosion, bent/broken pins, or loose terminals. Check for signs of water intrusion. Apply a small amount of dielectric grease before reconnecting to ensure a good seal and prevent future corrosion.
   Typical fix: Clean the connector terminals with electrical contact cleaner. If pins are bent, they can sometimes be carefully straightened. If the connector housing is damaged, it may need to be replaced with a pigtail connector.
   Est. part cost: $10-$30 for a pigtail connector.

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM/ECM): → Shop Engine Control Module (ECM) This is the least likely cause. The internal driver circuit for the cylinder 6 injector can fail, causing a permanent 'high' circuit condition. All other possibilities, especially wiring and the injector itself, must be exhaustively ruled out before condemning the PCM, as it is an expensive and complex repair requiring programming.

Diagnosis Steps

1. Read all stored DTCs and freeze frame data with an OBD-II scanner to understand the conditions when the fault occurred.
2. Crucial First Step for this Vehicle: Locate cylinder 6. On the transverse mounted V6, Bank 2 is toward the front of the vehicle (radiator side), and cylinder 6 is the cylinder on the driver's side of that bank.
3. Inspect Wiring: Carefully inspect the fuel injector wiring harness as described in TSB #PIP4924D. Pay close attention to areas where it contacts the intake manifold, the metal ECM bracket, and the cylinder head. Manipulate the harness with the engine running to see if it induces a misfire or stumble.
4. Check Connector: If no wiring damage is found, disconnect the connector at the cylinder 6 injector. Inspect for corrosion or damaged pins.
5. Noid Light Test: Use a noid light on the harness connector for cylinder 6. Start the engine. A rhythmic flashing light indicates the PCM is sending a proper signal. A steady-on light points to a short to voltage in the harness or a faulty PCM driver. No light indicates an open circuit.
6. Injector Resistance Test: Turn off the engine. Measure the resistance of the fuel injector with a multimeter. For the 3.6L LFX, it should be 1.2-1.8 Ohms. For the 3.0L LF1, it should be around 12 Ohms. A reading of infinity (OL) or near zero indicates a failed injector.
7. Injector Swap Test: As a definitive test, swap the cylinder 6 injector with another cylinder (e.g., cylinder 4 on the same bank). Clear codes and run the engine. If the code follows the injector (now showing P0271 for cylinder 4), the injector is confirmed to be the problem.
8. Circuit Integrity Test: If the code stays on cylinder 6 after the swap, the problem is in the wiring or the PCM. With the injector and PCM disconnected, check the injector control wire for a short to voltage (check for voltage with the key on) and for continuity to the PCM connector pin.
9. PCM Diagnosis: If all wiring and the injector are confirmed good, the final step is to suspect a faulty PCM driver, though this is rare.

Parts You'll Likely Need

• Fuel Injector Wiring Harness Repair Kit (OEM #ACDelco PT2183 (example pigtail)) — This is the most probable cause of P0277 on this vehicle, due to the known chafing issue documented in TSB #PIP4924D. Often only wire repair supplies are needed.
  Trusted brands: ACDelco, Dorman, 3M (for repair supplies)
  OEM price range: $20-$40 for a connector pigtail
  Aftermarket price range: $10-$30
• Fuel Injector (OEM #12634126 (for 3.6L LFX, supersedes 12642128)) — If the wiring is intact, the injector itself is the next most likely component to have failed with an internal electrical fault.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $100-$190
  Aftermarket price range: $50-$120

Related Codes That Often Appear With This One

• P0306 — P0306 means 'Cylinder 6 Misfire Detected'. Since a fuel injector circuit fault (P0277) prevents proper fueling of that cylinder, it will almost always cause a detectable misfire.
• P0206 — This code means 'Injector Circuit/Open - Cylinder 6'. It can appear alongside P0277 if the wiring issue is intermittent or presents as both an open and a short 🎬 Watch: Diagnosing injector circuit open malfunctions and common causes. to voltage depending on how the damaged wire moves.
• P219B — P219B indicates 'Bank 2 Fuel Trim Imbalance'. Since cylinder 6 is on Bank 2, a non-firing injector will cause that entire bank to run lean, which the PCM tries to correct, leading to an imbalance code.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: SES Light And Misfire With Injector Codes - Advises inspection of the fuel injector wiring harness for rub through or internal wire opens as a common cause for a list of injector codes including P0277.
• PI1067: ECM harness chafing on ECM bracket - Identifies a specific chafe point on the ECM bracket for similar vehicles.

Platform-Specific Known Issues

• TSB #PIP4924D: General Motors issued this bulletin for a wide range of vehicles, including the 2010-2014 SRX, that use the 3.0L and 3.6L V6 engines. It specifically calls out that injector codes like P0277 are often caused by the fuel injector wiring harness rubbing through against engine components. Technicians are advised to carefully inspect the harness for damage before replacing any parts.
• **Related T

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (3.6L LFX V6) — expected: 1.2 - 1.8 Ohms. Failure: A reading of OL (open), near zero (short), or significantly outside the specified range.
• Fuel Injector Resistance (3.0L LF1 V6) — expected: ~11 - 14 Ohms. Failure: A reading significantly different from the 11-14 Ohm range.
• Injector Pulse Width (at idle, warmed up) — expected: 2.0 - 4.0 milliseconds (ms). Failure: A value of 0 ms for cylinder 6 while others are pulsing indicates the ECM has shut down the driver. A value significantly different from other cylinders can also indicate a problem.
• Injector Balance Test (Pressure Drop) — expected: All injectors should have a pressure drop within 20 kPa (3 psi) of the average.. Failure: An injector with a pressure drop significantly higher or lower than the others, or no drop at all, indicates a flow issue or a non-firing injector.

Scan Tool Commands That Help

• GDS2 / Tech2: Injector Balance Test — This automated test commands the ECM to pulse each injector individually while monitoring the fuel rail pressure drop. It's used to identify injectors that are clogged, leaking, or not firing, by comparing the pressure drop of each injector to the others. A significant deviation on cylinder 6 would point to a problem with that injector or its circuit.
• GDS2 / High-End Bidirectional Scanner: Cylinder Power Balance / Injector Kill — This active test allows the technician to manually disable one injector at a time while the engine is running. When a healthy cylinder's injector is disabled, there should be a noticeable drop in RPM. If disabling cylinder 6 causes no change in RPM, it confirms that cylinder was not contributing power, likely due to the injector fault.

Wiring & Ground Locations

• ECM Connector X1 (3.6L LFX) — At the Engine Control Module (ECM) in the engine bay. On the LFX, the ECM has three main connectors (X1, X2, X3). X1 is typically identified by a Blue terminal position assurance clip.. This connector contains the control wire for the cylinder 6 fuel injector. A poor connection, corrosion, or backed-out pin at this specific location can cause an open or high resistance in the circuit, triggering P0277.
• Cylinder 6 Injector Control Wire (3.6L LFX) — On a similar GM 3.6L V6, the injector 6 control wire is a Yellow/Black wire located at Pin 64 of the ECM connector. The power feed wire to the injector is typically Pink/Black. This should be verified with a vehicle-specific diagram.. Knowing the specific pin and wire color is essential for testing continuity between the ECM and the injector connector, and for checking for shorts to voltage or ground without guesswork.
• G107 Engine Ground — On the 3.6L LFX engine, a key ground designated G107 is located on the upper left front side of the engine, often on the cylinder head.. The ECM and its injector driver circuits rely on clean, solid ground connections. A loose or corroded G107 ground can introduce electrical noise or voltage offsets, potentially causing the ECM to misinterpret the injector circuit's state and set false codes like P0277.

OEM Part Supersession History

• 12642128 → 12634126 — Part update/revision by the manufacturer.
  Heads up: Applies to the 3.6L LFX V6 engine (2012-2014). The newer part number is the correct service replacement.
• 12629927 → ACDelco 217-3449 — Part update and transition to service part number.
  Heads up: Applies to the 3.0L LF1 V6 engine (2010-2011). These are high-impedance injectors and are not interchangeable with the LFX injectors.

Model Year Variations Within This Range

• 2010-2011 vs 2012-2014: The primary difference is the engine: 2010-2011 models use the 3.0L LF1 V6, while 2012-2014 models use the 3.6L LFX V6. They use different fuel injectors (high-impedance ~12 Ohm for LF1 vs. low-impedance ~1.5 Ohm for LFX) and different ECMs (Bosch family for LF1 vs. Delphi for LFX). These parts are not interchangeable.