P0274 on 2011-2014 Chevrolet Camaro: Cylinder 5 Injector Circuit High Causes and Fixes

What's Unique About the 2011-2014 Chevrolet CAMARO

For this generation of Camaro, General Motors issued a Technical Service Bulletin (TSB #PIP4924D) specifically warning technicians about the fuel injector wiring harness rubbing through its insulation. This chafing against engine components like the ECM/TCM bracket, upper control arm, and shock tower bolt is a well-documented weak point and a primary suspect for P0274. 🎬 Watch: Diagnosing misfire codes on a fifth-gen Chevy Camaro. A thorough harness inspection is the critical first step before assuming the injector itself has failed.

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
• Engine running rough or vibrating, especially at idle
• Noticeable loss of power and sluggish acceleration
• Reduced fuel economy
• Engine misfire, which may also trigger a P0305 code
• "Service StabiliTrak" message may appear on the driver information center
• Strong fuel smell from the exhaust

Most Likely Causes

1. Chafed Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness A known issue documented in GM TSB #PIP4924D and reinforced by patterns in TSB #21-NA-149. The harness routing can cause it to rub against sharp edges, leading to a short to voltage.
   How to confirm: Visually inspect the entire fuel injector harness, paying close attention to points where it contacts the intake plenum, valve cover bolts, fuel lines, the ECM/TCM bracket, and the side of the cylinder head. Look for worn insulation, exposed copper wires, or burn marks. The chafing can be subtle and may require moving the harness to see.
   Typical fix: Repair the damaged section of wire by soldering and using heat-shrink tubing. If the damage is close to the connector, replace it with a new pigtail (GM Part #88988506). Protect the repaired area with anti-abrasion tape or loom and re-route or secure it with zip ties to prevent future rubbing.
   Est. part cost: $15-$60
2. Faulty Cylinder 5 Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Injectors can fail electrically over time, developing an internal short that causes a high circuit voltage condition. High ethanol content in fuel can also accelerate wear.
   How to confirm: Swap the cylinder 5 injector with an injector from another cylinder (e.g., cylinder 3). If the code changes to P0268 (for cylinder 3), the injector is faulty. Alternatively, check the injector's resistance with a multimeter; a healthy GM direct injector should read between 1.5 and 1.6 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 that bank, or the full set, if they are high-mileage. For the 3.6L LFX, the original injector (12634126) has been superseded by part number 12669384.
   Est. part cost: $70-$180
3. Corroded or Loose Injector Connector ⚪ Low Probability Vibration and heat cycles can cause the connector pins to loosen or corrode over time, creating high resistance.
   How to confirm: Disconnect the electrical connector at the cylinder 5 fuel injector and inspect the terminals for corrosion (white or green powder), moisture, or bent/backed-out pins. Ensure it clicks securely when reconnected.
   Typical fix: Clean the connector terminals with electrical contact cleaner and apply a small amount of dielectric grease to prevent future moisture intrusion. If pins are damaged, replace the pigtail connector.
   Est. part cost: $15-$30

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is rare, but if the wiring and injector are confirmed to be good, the injector driver circuit within the PCM may have failed. This should be the last item to check due to its cost and complexity.
• Poor Engine or Chassis Grounds: The 5th Gen Camaro platform is known for having potential grounding issues that can cause a wide range of electrical gremlins, including misfires and sensor faults. Check that the main engine-to-chassis ground straps are clean, tight, and free of corrosion. Some owners add a supplementary ground wire to improve reliability.

Diagnosis Steps

1. Read all fault codes with an OBD-II scanner. Note any other codes, especially P0305.
2. Inspect the Wiring Harness: This is the most important first step for this vehicle. Carefully inspect the fuel injector harness for chafing, especially against the ECM/TCM bracket, valve cover bolts, and shock tower, as noted in TSBs #PIP4924D and #21-NA-149.
3. Check the Connector: Disconnect and inspect the cylinder 5 injector connector for corrosion or damaged pins. Ensure it's securely seated.
4. Perform an Injector Swap: If no wiring damage is found, swap the cylinder 5 fuel injector with one from an adjacent cylinder. Clear the codes and run the engine. If the fault code moves to the new cylinder (e.g., P0268 for cylinder 3), the injector is bad.
5. Test the Circuit: If the code remains on cylinder 5 after the swap, use a noid light to verify the PCM is sending a pulse signal to the injector connector. A steady light or no light indicates a wiring or PCM problem.
6. Test the Injector Resistance: With a multimeter, measure the resistance across the two terminals of the suspect injector. Compare the reading to the manufacturer's specification (specifically 1.5-1.6 ohms for GM 3.6L DI engines). An out-of-spec reading confirms an internal injector fault.
7. Check for a Short to Voltage: If the injector and its pulse are good, use a multimeter to check the control wire between the PCM and the injector for a short to a voltage source.
8. Inspect Grounds: Check the main engine and chassis ground connections (e.g., G102, G105, G106) for tightness and corrosion, as poor grounds can cause erratic electrical behavior.
9. Consider the PCM: If all other tests pass, the issue may be an internal failure of the PCM's injector driver circuit, though this is uncommon.

Parts You'll Likely Need

• Fuel Injector (OEM #12669384 (supersedes 12634126 for 3.6L V6 LFX), 12613412 (for 6.2L V8 LS3/L99)) — The injector can fail internally, causing an electrical short or open that triggers the 'Circuit High' code.
  Trusted brands: ACDelco, GM Genuine Parts, Bosch
  OEM price range: $120-$180
  Aftermarket price range: $70-$110
• Fuel Injector Connector Pigtail (OEM #88988506 (also listed as ACDelco PT2188)) — Used to repair the wiring harness if it is found to be chafed or damaged near the injector connector.
  Trusted brands: Dorman, ACDelco, GM Genuine Parts
  OEM price range: $25-$50
  Aftermarket price range: $15-$25

Related Codes That Often Appear With This One

• P0305 — P0305 indicates a misfire on cylinder 5. Since P0274 causes the cylinder 5 injector to malfunction, a misfire on that cylinder is a direct consequence.
• P0205 — P0205 indicates a general malfunction in the cylinder 5 injector circuit. It can appear alongside P0274 as the PCM tries to diagnose the electrical fault.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Warns of potential for the fuel injector wiring harness to rub through or have internal wire opens, causing various injector-related DTCs including P0274.
• 21-NA-149: Details specific engine wiring harness chafe points on other GM vehicles (ECM bracket, upper control arm, shock tower) that are valuable inspection areas for any GM vehicle of this era, including the Camaro.

Platform-Specific Known Issues

• A General Motors Technical Service Bulletin (TSB #PIP4924D) was issued for multiple vehicles, including the 2011-2014 Camaro, for a condition where the fuel injector wiring harness can rub through against various engine components. This chafing can cause a short circuit and trigger a variety of injector codes, including P0274. Specific inspection points mentioned are the intake plenum, valve cover bolts, and fuel lines.
• A later TSB, #21-NA-149, further details engine harness chafing issues on various GM trucks and SUVs, highlighting common failure points like the ECM/TCM bracket, the upper control arm, and the shock tower bolt. While for different vehicles, this bulletin reinforces the known pattern of GM harness routing issues causing electrical faults, which is highly relevant to the Camaro's diagnosis.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (3.6L LFX/LLT Direct Injection) — expected: 1.5 - 1.6 Ω. Failure: A reading significantly higher or lower than this range, or an open circuit (infinite resistance).
• Fuel Injector Power Supply Voltage (Key On, Engine Off) — expected: 12.0 - 12.6 V (Battery Voltage). Failure: No voltage, or voltage significantly lower than battery voltage, indicates a problem with the power supply circuit or fuse.
• Injector Pulse Width at Idle (Scan Tool) — expected: ~3.4 ms. Failure: A value that is drastically different or erratic may indicate a control problem, though this is a secondary check.

Scan Tool Commands That Help

• GDS2, Tech2, or equivalent professional bidirectional scanner (Autel, Launch, XTOOL): Injector Balance Test / Power Balance Test — Use this test when a misfire (P0305) is present with P0274. The command allows you to individually disable the cylinder 5 injector. If disabling it causes no change in engine RPM drop compared to other cylinders, it confirms cylinder 5 is not contributing, pointing strongly to a fault in its fuel delivery.
• GDS2, Tech2, or equivalent professional bidirectional scanner: Injector Test — This function can command the injector to click with the engine off (but key on), allowing the technician to listen for the injector's mechanical actuation with a stethoscope to verify it's not mechanically seized.

Wiring & Ground Locations

• Cyl 5 Injector Wires (LFX V6) — At the ECM connectors. The two wires for the cylinder 5 injector are Light Green/White and Light Green.. These wires are found at pins 28 and 29 of the ECM connector. Knowing the specific pins and colors is essential for testing continuity and checking for shorts between the injector and the ECM without having to strip the harness.
• G102 — Located at the left rear of the engine.. This ground point is for the ignition coils. While not directly for the injectors, a poor ground here can cause electrical noise and misfires that may complicate diagnosis.
• G105 / G106 — G105 is at the left front of the engine compartment behind cooling fan relays. G106 is on the front center of the frame cross rail, under the crank pulley.. These are major engine compartment and chassis grounds. The ECM and its related circuits rely on clean, tight connections at these points. A corroded or loose main ground can cause floating voltages and trigger 'Circuit High' codes.
• Cylinder Head Grounds — There are ground points located on the back of each cylinder head.. These are primary engine-to-harness ground points. Given the proximity to the injector harness, ensuring these are clean and tight is a critical step when diagnosing any engine electrical fault.

OEM Part Supersession History

• 12634126 → 12669384 — Standard part update for improved performance, reliability, or manufacturing efficiency.

Model Year Variations Within This Range

• 2011 vs 2012-2014 (V6 Models): The 2011 model year used the 3.6L LLT V6 engine. For the 2012 model year, GM introduced the updated 3.6L LFX V6. The LFX features a different cylinder head with an integrated exhaust manifold, a new composite intake manifold, and different fuel injectors. While the P0274 diagnosis is similar, technicians should be aware that wiring harness routing and specific injector part numbers differ between the LLT and LFX engines.