P0268 on 2012-2014 Chevrolet Impala: Cylinder 3 Injector Circuit High Causes and Fixes

What's Unique About the 2012-2014 Chevrolet IMPALA

While any car can have a bad injector, the 2012-2014 Impala and other GM vehicles with the 3.6L V6 engine are known for a specific wiring harness issue that triggers this code. A General Motors TSB (#PIP4924D) explicitly directs technicians to inspect the fuel injector wiring harness for chafing and damage when P0268 and other related codes appear. The harness can rub against the intake plenum, valve cover bolts, fuel lines, or the side of the cylinder head, causing a short circuit that the PCM interprets as a 'Circuit High' condition. This vulnerability is so prevalent that inspecting the harness is the mandatory first step before considering other causes.

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 covers the end of the ninth generation (2006-2013) and the start of the tenth generation (2014-2020). In 2014, Chevrolet sold both the old design as the "Impala Limited" and the new tenth-generation model. Both generations offered the 3.6L LFX V6 engine, and the information in this guide, particularly the TSB regarding wiring, is applicable to this engine across both generations and numerous other GM vehicles.

Symptoms You May Notice

• Check Engine Light is on (may be flashing)
• Engine misfire, which may feel like a shake, stumble, or a distinct buck/jerk.
• Rough idle.
• Reduced engine power and poor, sluggish acceleration.
• Decreased fuel economy.
• Engine may stall at low speeds or idle.

Most Likely Causes

1. Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As documented in GM TSB #PIP4924D, the wiring harness for the fuel injectors is prone to chafing against engine components. Common chafe points include the intake plenum, valve cover bolts, fuel lines, and the side of the cylinder head. Engine vibrations cause the harness to rub against these sharp or abrasive surfaces, eventually wearing through the insulation and causing a short to power.
   How to confirm: With the engine off and the intake manifold removed for access, carefully trace the wiring harness leading to the cylinder 3 fuel injector. Visually and physically inspect for any signs of rubbing, melting, or exposed copper wire. Pay extremely close attention to the specific chafe points mentioned in the TSB. A continuity test from the injector connector to the PCM connector can identify an open or shorted wire.
   Typical fix: Repair the damaged section of the wire. This involves cutting out the bad section, splicing in a new piece of wire (preferably using solder and heat-shrink connectors), and protecting the repair with split-loom tubing to prevent future damage. If damage is at the connector, replace the connector pigtail.
   Est. part cost: $5-$30
2. Faulty Cylinder 3 Fuel Injector 🟡 Medium Probability → Shop Fuel Injector The LFX engine uses low-impedance direct injectors which can fail internally, causing a short. While less common than the wiring issue, it is a frequent point of failure.
   How to confirm: After confirming the wiring is intact, test the injector. Use a multimeter to measure the resistance across the two pins of the injector; for the 3.6L LFX, it should be between 1.2 and 1.8 ohms. A reading near zero indicates a short. A definitive test is to swap the cylinder 3 injector with another cylinder (e.g., cylinder 1). Clear the codes and run the engine. If the code changes to P0262 (Cylinder 1 Injector Circuit High), the injector is faulty.
   Typical fix: Replace the faulty fuel injector. It is recommended to replace the Teflon seal and O-rings at the same time. Due to the difficulty of access, some mechanics recommend replacing all three injectors on the firewall-side bank at once.
   Est. part cost: $60-$120
3. Powertrain Control Module (PCM) Failure ⚪ Low Probability → Shop Engine Control Module (ECM) An internal short in the injector driver circuit within the PCM can cause this code. This is sometimes the result of an external short in the wiring or injector damaging the PCM's internal driver transistor.
   How to confirm: This is typically diagnosed by a professional after exhaustively ruling out all wiring and component faults. Advanced scan tools are needed to monitor the injector driver output from the PCM. This should be the absolute last part considered for replacement.
   Typical fix: Replace and reprogram the Powertrain Control Module. This usually requires a professional shop or dealer with access to GM's programming software.
   Est. part cost: $300-$800

Rare But Worth Checking

• Bent or Corroded Connector Pins: Check the pins on both the injector and the harness connector. Moisture can cause corrosion, and improper connection can bend the pins, leading to a poor connection or a short. Also check the main harness connector (X161) at the top rear of the engine for corrosion.

Diagnosis Steps

1. Verify the code with an OBD-II scanner and check for any other related codes like P0303. Note the freeze frame data.
2. Identify Cylinder 3. On the transversely mounted 3.6L LFX V6 in the Impala, the cylinders against the firewall (rear bank) are 1, 3, and 5 (from passenger to driver side). The cylinders at the front of the car (radiator side) are 2, 4, and 6. Cylinder 3 is the middle cylinder on the rear bank, against the firewall. Access requires removal of the upper intake manifold.
🎬 Watch: Step-by-step guide to removing the LFX intake manifold.
3. Perform a thorough visual inspection of the wiring harness and connector for cylinder 3, paying close attention to areas where it might rub against the engine, as noted in TSB #PIP4924D: intake plenum, valve cover bolts, fuel lines, and the side of the cylinder head.
4. If no visible damage is found, disconnect the injector and use a 'noid light' to test for a signal from the PCM at the connector. A steady light or no light when the engine is cranking indicates a problem. A healthy signal is a consistent flashing light.
5. With the injector unplugged, use a multimeter set to Ohms to measure the resistance across the two pins on the injector itself. For the LFX engine, a good reading is between 1.2 and 1.8 ohms. A reading near 0 ohms indicates a shorted injector.
6. If the wiring looks good and the injector resistance is correct, consider swapping the injector with another cylinder (e.g., cylinder 1) to see if the fault follows the injector. If P0268 returns, the problem is in the wiring or PCM; if code P0262 appears, the injector is bad.
7. If the problem persists on cylinder 3 after swapping the injector, perform a continuity test on the two wires running from the PCM connector to the injector connector to check for shorts or breaks in the harness. Check for a short to power on the control wire (often Dark Blue/White at ECM pin 49 on some models).
8. If all wiring and the injector prove to be good, the fault may lie within the PCM itself, which requires professional diagnosis.

Parts You'll Likely Need

• Fuel Injector (OEM #12634126) — If the injector itself has failed its resistance test or is confirmed faulty after a swap test, it will need to be replaced. This part number is for the LFX engine and often supersedes 12642128.
  Trusted brands: ACDelco (GM Genuine), Bosch, Standard Motor Products
  OEM price range: $80-$120
  Aftermarket price range: $50-$90
• Fuel Injector Connector Pigtail (OEM #ACDelco PT2183 / GM 88988963) — If the plastic connector that plugs into the injector is broken, corroded, or the wiring is damaged right at the connector, a new pigtail will need to be spliced into the harness.
  Trusted brands: ACDelco, Dorman (645-595), Standard Motor Products (S-754)
  OEM price range: $20-$40
  Aftermarket price range: $10-$25
• Upper Intake Manifold Gasket 🎬 Watch: Detailed video on removing the upper intake manifold. Set — These gaskets must be replaced anytime the upper intake manifold is removed to access the fuel injectors on the 3.6L V6 engine.
  Trusted brands: Fel-Pro, ACDelco
  OEM price range: $30-$50
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• P0303 — This code means 'Cylinder 3 Misfire Detected'. It is a direct and expected symptom of P0268, as the disabled injector circuit prevents fuel from being delivered to cylinder 3, causing it to misfire.
• P0203 — This code for 'Injector Circuit/Open - Cylinder 3' can sometimes appear with P0268. It points to a general electrical fault in the same circuit, and an intermittent short can sometimes be interpreted as an open circuit by the PCM.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Instructs technicians to inspect the fuel injector wiring for damage when encountering various injector circuit codes, including P0268, P0201-P0206, and many others. It points to specific chafe points on the harness.

Platform-Specific Known Issues

• TSB #PIP4924D: This official General Motors bulletin addresses multiple fuel injector circuit codes, including P0268. It specifically instructs technicians to inspect the fuel injector wiring harness for chafing against the engine, which can cause a short circuit. Specific chafe points mentioned are against the intake plenum, valve cover bolts, fuel lines, and the side of the cylinder head.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (3.6L LFX V6) — expected: 1.2 - 1.8 Ohms. Failure: A reading near 0 ohms (short), infinity/OL (open), or outside this specific range.
• Injector Pulse Width (at normal idle) — expected: 2 - 4 milliseconds (ms). Failure: A value of 0 ms on cylinder 3 while other cylinders show a pulse, indicating the ECM has shut down the injector.
• Injector Control Circuit Voltage (Key On, Engine Off) — expected: 0V. Failure: A reading near battery voltage (12V) on the control wire indicates a short to power in the harness.
• High-Pressure Fuel Rail Pressure (at idle) — expected: 300-350 kPa (approx. 44-51 PSI). Failure: While not a direct cause of P0268, significant deviation can point to other fuel system issues.

Scan Tool Commands That Help

• GM GDS2 / Tech2 or equivalent professional scanner: Fuel Injector Balance Test — This is a crucial active test to perform after electrical checks are complete. The tool commands each injector to fire and measures the drop in fuel rail pressure. It can identify a mechanically faulty or clogged injector that might still pass a resistance test, or confirm that an injector is not firing at all. A significant variance (GM often specifies <20%) in pressure drop for cylinder 3 points to an issue.
• GM GDS2 / most bidirectional scanners: Cylinder Power Balance / Injector Kill — This function disables one injector at a time while the engine is running. When a good cylinder is disabled, engine RPM will drop. If disabling cylinder 3 causes little or no change in RPM, it confirms that cylinder is not contributing power, which is the expected result with an active P0268 fault.

Wiring & Ground Locations

• Injector 3 Control Wire — On some 3.6L LFX models, this is a Dark Blue/White wire at Pin 49 of the X1 connector at the Engine Control Module (ECM).. This is the specific wire the ECM uses to ground-pulse the #3 injector. Testing for a short-to-power on this wire is a definitive diagnostic step. If this wire is chafed and touching a power source, it will cause P0268.
• G102 — A primary engine-related ground point located near the battery.. A poor or corroded ground at this location can cause unstable voltage references for the ECM and its various sensors and actuators, potentially leading to erroneous circuit high codes.
• G111 — An engine ground point located above the starter motor.. This is a critical ground for engine block components. Corrosion or looseness here can create a host of electrical issues, including problems with sensor and actuator circuits controlled by the ECM.
• Main Engine-to-Chassis Ground — A large ground strap running from the engine block (often near the starter or on the front left side) to the vehicle's frame/chassis.. This is the primary path for all electrical current returning from the engine. A weak connection here can cause the ECM and other modules to seek alternative, higher-resistance ground paths, leading to unpredictable voltage readings and faults.

Real Owner Repair Stories

• traverseforum.com user (2011 Chevrolet Traverse 3.6L (LLT, but same TSB applies)) — Check engine light with codes P0268 (Cyl 3 Injector Circuit High) and P0303 (Cyl 3 Misfire).
  ❌ Tried (didn't work) Initial diagnosis pointed towards a bad injector or PCM.
  ✅ What actually fixed it The user found the injector wiring harness was chafing against the A/C line bracket near the firewall. The insulation on the wire for the #3 injector was worn through, causing it to short out. The fix was to repair the damaged wire and protect the harness to prevent it from happening again. This directly confirms the issue described in TSB #PIP4924D.

OEM Part Supersession History

• 12642128 → 12634126 — Standard part revision and update by the manufacturer for the LFX engine.
  Heads up: Part number 12634126 is correct for the 2012+ 3.6L LFX engine. The earlier 2009-2011 3.6L LLT engine uses a different, high-impedance injector (e.g., 12638530). Using the wrong injector will cause immediate running issues and codes.

Model Year Variations Within This Range

• 2012-2014: The 2012 model year marked the switch from the 3.6L LLT V6 to the updated 3.6L LFX V6. The LFX engine features low-impedance injectors (~1.2-1.8 Ohms), a composite intake manifold, and integrated exhaust manifolds. The prior LLT engine used high-impedance injectors (~12 Ohms). Using the wrong resistance specification for testing will lead to a misdiagnosis.