P0262 on 2009-2014 GMC Acadia: Cylinder 1 Injector Circuit High Causes and Fixes

What's Unique About the 2009-2014 Gmc ACADIA

On the 3.6L V6 engine in the first-generation Acadia and its platform mates (Buick Enclave, Chevy Traverse, Saturn Outlook), this code is often more than just a single bad injector. A well-documented GM Technical Service Bulletin (TSB #PIP4924D) highlights that electrical issues within the main engine harness can cause P0262 and a host of other injector circuit codes simultaneously. The TSB specifically calls out common chafe points for the harness, such as "against the intake plenum, at valve cover bolts, against the fuel line and on the side of the head under the plenum." This makes a thorough inspection of the wiring harness a critical first step, potentially saving you from replacing a perfectly good injector.

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 or on or flashing
• Rough or shaky engine idle
• Engine misfire, which may feel like a stumble or hesitation
• Poor acceleration and loss of power
• Reduced fuel economy
• Hard starting or extended cranking
• Strong smell of fuel from the exhaust

Most Likely Causes

1. Failed Cylinder 1 Fuel Injector 🔴 High Probability → Shop Fuel Injector Injectors can fail electrically over time, developing an internal short that causes a high voltage condition. This is a common failure item on high-mileage GM 3.6L engines.
   How to confirm: Disconnect the injector and measure the resistance across its two terminals with a multimeter. Compare the reading to the manufacturer's specification (typically 11-14 ohms). 🎬 Watch: Professional guide to testing 3.6L injector resistance and waveforms. A reading of zero or very low resistance indicates an internal short. A reading significantly outside the specification suggests the injector is faulty.
   Typical fix: Replace the cylinder 1 fuel injector. Due to the labor involved in removing the intake manifold, it is often recommended to replace all injectors on that bank 🎬 See this walkthrough for active injector testing and removal steps. (Bank 1), or all six, if they are original and high-mileage.
   Est. part cost: $45-$140
2. Wiring Harness or Connector Issue 🔴 High Probability As noted in TSB PIP4924D, the engine harness is prone to chafing and developing faults. Specific problem areas include rubbing against the intake plenum, valve cover bolts, fuel lines, and the side of the cylinder head. This can cause a short to voltage on the injector control wire.
   How to confirm: Visually inspect the wiring harness leading to the cylinder 1 injector, paying close attention to the chafe points listed in TSB PIP4924D. Look for any signs of melting, rubbing, or corrosion. Check the connector for damaged pins, corrosion, or oil contamination. Use a multimeter to check the control wire for voltage with the key on, engine off; it should read 0 volts. Voltage on this wire indicates a short in the harness.
   Typical fix: Repair the damaged section of the wiring harness. If the connector is damaged, it can be replaced with a pigtail kit. In severe cases, a bank-specific injector harness may need to be replaced.
   Est. part cost: $15-$200

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is the least likely cause. The internal driver circuit for the injector can fail, but this should only be considered after thoroughly ruling out the injector and all wiring issues.

Diagnosis Steps

1. Scan the vehicle for trouble codes and confirm P0262 is present. Note any other codes, especially other injector codes which would point to a harness issue.
2. Locate cylinder 1. On the transverse 3.6L V6, this is the front cylinder on the bank closer to the firewall (Bank 1).
3. Visually inspect the wiring harness and connector for the cylinder 1 fuel injector. Pay close attention to known chafe points: against the intake plenum, valve cover bolts, and fuel lines.
4. Disconnect the injector connector. Use a multimeter to measure the resistance (ohms) across the two pins on the injector itself. A normal reading is between 11-14 ohms. A significantly lower reading indicates a shorted injector.
5. With the injector still disconnected and the key on (engine off), test the two wires in the connector. One should have battery voltage (power feed). The other is the control wire from the PCM and should have 0 volts. 🎬 Watch: How to test injector circuits using a multimeter and light. If the control wire has voltage, there is a short in the harness.
6. If the injector and wiring test good, consider swapping the cylinder 1 injector with another one (e.g., cylinder 3). Clear the codes and run the engine. If the code changes to P0268 (Cylinder 3 Injector Circuit High), the injector is confirmed to be faulty. If P0262 returns, the problem is intermittent or lies in the wiring or PCM.
7. For advanced diagnosis, use a lab scope to observe the voltage pattern on the injector control wire. A healthy signal will show a square wave when the engine is running. A flat line or constant voltage points to a wiring or PCM driver issue.
8. If all other tests pass, the fault may lie within the PCM, which requires professional diagnosis and likely replacement/reprogramming.

Parts You'll Likely Need

• Fuel Injector (OEM #12663380 (for 2012-2014 LFX) or 12638530 (for 2009-2011 LLT)) — The most common cause for P0262 is an internally shorted fuel injector. Part numbers differ between the LLT and LFX engines.
  Trusted brands: ACDelco, Bosch
  OEM price range: $80-$140
  Aftermarket price range: $45-$90
• Upper and Lower Intake Manifold Gaskets — Replacing the fuel injectors on the 3.6L V6 requires removing the intake manifold. The gaskets are single-use and must be replaced to prevent vacuum leaks.
  Trusted brands: Fel-Pro, Mahle, ACDelco
  OEM price range: $40-$70
  Aftermarket price range: $25-$50
• Fuel Injector Connector Pigtail (OEM #ACDelco PT2160 or Standard Motor Products S-1024) — If the connector at the injector is corroded, melted, or has broken locking tabs, a replacement pigtail is needed to splice into the harness.
  Trusted brands: ACDelco, Standard Motor Products (SMP), Dorman
  OEM price range: $25-$40
  Aftermarket price range: $10-$25
• Bank-Specific Injector Harness (OEM #12621095 (Bank 2/Left/Front) or 12621096 (Bank 1/Right/Rear)) — If the wiring harness for an entire cylinder bank is damaged beyond simple repair (e.g., extensive melting or multiple breaks), the entire sub-harness may need to be replaced.
  Trusted brands: GM Genuine Parts
  OEM price range: $160-$200

Related Codes That Often Appear With This One

• P0301 — This code means 'Cylinder 1 Misfire Detected,' which is a direct and immediate result of the fuel injector not functioning correctly due to the P0262 fault.
• P0261, P0264, P0265, P0267, P0268, etc. — The appearance of multiple injector circuit codes at once strongly suggests a common wiring harness problem affecting an entire cylinder bank, as described in TSB PIP4924D.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Addresses engine misfires with multiple injector circuit codes (P0262, etc.). Recommends carefully inspecting the fuel injector wiring harness for rub-through or open circuits at common chafe points: "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

• A known issue, documented in GM TSB #PIP4924D, involves the engine wiring harness. It can chafe or have poor terminal connections, leading to various injector circuit codes, including P0262. Specific inspection points are where the harness may rub against the intake plenum, valve cover bolts, the main fuel line, and the side of the cylinder head.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance — expected: 11-14 ohms. Failure: A reading significantly lower (indicating a short) or higher (indicating an open circuit) than the specified range.
• Injector Control Circuit Voltage (Key On, Engine Off) — expected: 0 Volts. Failure: Any voltage reading on the control wire indicates a short to voltage in the wiring harness.
• Injector High Voltage Supply Circuit (Cranking/Running) — expected: Test lamp flashes. Failure: If the test lamp does not flash or stays on continuously, it indicates a problem with the supply circuit or the ECM driver.

Scan Tool Commands That Help

• GDS2 / Tech2: Injector Control Circuit Test Status — Use this parameter while performing a 'wiggle test' on the wiring harness. If the status changes from 'OK' or 'Not Run' to 'Fault', it confirms an intermittent open or short in the circuit you are moving.
• GDS2 / Tech2: Fuel Injector Coil Test — This is an automated test run by the scan tool to help isolate an intermittent electrical condition within the injector's solenoid coil.
• GDS2 / Tech2: Injector Balance Test — While P0262 is an electrical code, if you suspect a related mechanical issue, this test can command each injector to fire and measure the corresponding pressure drop in the fuel rail to identify a clogged or underperforming injector.

Wiring & Ground Locations

• X160 / X161 — Multi-way harness connectors located at the rear of the intake manifold.. These are the primary connectors separating the main engine harness from the injector sub-harnesses. Disconnecting here allows a technician to isolate and test the wiring going to the ECM versus the wiring going to the injectors.
• G112 — Rear of the engine, mounted to the rear of the cylinder head.. This is a critical engine ground. A poor connection here can cause a variety of phantom electrical issues and incorrect sensor readings for components grounded on the engine block.
• G114 — Left rear of the engine.. Another key engine ground point. Verifying it is clean and tight is a crucial step in diagnosing any electrical fault code.
• ECM (Engine Control Module) — Left side of the engine compartment.. This is the location of the computer that controls the injectors. Final wiring checks will be performed at the ECM connector pins to confirm if the fault is in the harness or internal to the module.

OEM Part Supersession History

• 12638530 → 12669384 — Standard part revision and update by the manufacturer.
  Heads up: This is a port fuel injector (PFI) and is not compatible with the later LFX direct injection engine.
• 12634491 → 12663380 — Standard part revision and update by the manufacturer.
  Heads up: This is a gasoline direct injector (GDI) and is not compatible with the earlier LLT port injection engine.
• N/A → N/A — N/A
  Heads up: One parts supplier recommends replacing all injectors as a set, noting that mixing new genuine parts with older or aftermarket parts can cause issues due to potential differences in oil output and atomization concentration.

Model Year Variations Within This Range

• 2009-2011: These models use the 3.6L LLT V6 engine with Port Fuel Injection (PFI). The injectors (PN 12638530, superseded by 12669384) operate on a lower voltage 12-volt system.
• 2012-2014: These models use the updated 3.6L LFX V6 engine with Gasoline Direct Injection (GDI/SIDI). The injectors (PN 12663380) are different and operate on a high-voltage circuit supplied and controlled by the ECM. Diagnostic procedures for the high-voltage supply and control circuits are specific to this engine.