P0261 on 2009-2014 Buick LaCrosse: Injector Circuit Low Causes and Fixes

What's Unique About the 2009-2014 Buick LACROSSE

For this generation of Buick LaCrosse, especially models equipped with the 3.0L and 3.6L V6 engines, General Motors issued a Technical Service Bulletin (TSB #PIP4924D) that directly addresses this and other injector circuit codes. The TSB points to a known issue where the fuel injector wiring harness is prone to rubbing against parts of the engine like the intake plenum, valve cover bolts, or fuel lines. This makes a wiring fault a significantly higher probability on these specific vehicles compared to 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.

Generation note: The 2009-2014 range covers the end of the first generation (2009) and the beginning of the second generation (2010-2014) LaCrosse. The engines differ, with the 2009 model offering 3.8L V6, 3.6L V6, and 5.3L V8 options, while 2010-2014 models used 2.4L I4, 3.0L V6, and 3.6L V6 engines. The relevant TSB (PIP4924D) specifically covers the 3.0L and 3.6L V6 engines common in this range, making the wiring harness issue a primary concern for V6 models.

Symptoms You May Notice

• Check Engine Light is on
• Rough or shaking idle
• Engine misfire, which may feel like a tapping or shuddering
• Reduced engine power and poor acceleration
• Hesitation or stumbling when pressing the gas pedal
• Decreased fuel economy
• Hard starting condition

Most Likely Causes

1. Fuel Injector Wiring Harness Chafed or Shorted 🔴 High Probability → Shop Engine Wiring Harness GM Technical Service Bulletin PIP4924D specifically calls out this issue on these engines. The harness routing can cause it to rub against the intake plenum, valve cover bolts, or fuel lines, eventually wearing through the insulation and causing a short to ground. This is the most common cause by a significant margin for this specific vehicle and code.
   How to confirm: Visually inspect the entire fuel injector harness, paying close attention to the areas mentioned in the TSB: where it passes the intake plenum, near valve cover bolts, against the high-pressure fuel line, and on the side of the cylinder head under the plenum. Look for any signs of rubbing, melting, or exposed copper wires. Use a multimeter to check for continuity to ground on the control wire for the cylinder 1 injector with the harness disconnected from the ECM.
   Typical fix: Repair the damaged section of the wire by splicing in a new piece of wire with solder and heat shrink tubing. Protect the repaired area and the rest of the harness with a protective wire loom or conduit. Re-route the harness slightly if possible to create more clearance and prevent future rubbing. In severe cases where multiple wires are damaged, the entire injector harness bank may need to be replaced (e.g., GM Part #12621095 for the left bank).
   Est. part cost: $5-$50 for repair materials, $100-$160 for a new harness bank.
2. Faulty Cylinder 1 Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Direct injection (DI) fuel injectors operate under high pressure and can fail internally, causing a short or open circuit in the coil.
   How to confirm: Swap the cylinder 1 fuel injector with another cylinder's injector (e.g., cylinder 3). Clear the codes and run the engine. If the code changes to P0267 (Cylinder 3 Injector Circuit Low), the injector is faulty. You can also check the injector's resistance with a multimeter (if specifications are available for your specific injector part number); an out-of-spec reading indicates failure. A reading of 0 ohms or very low resistance indicates a shorted injector.
   Typical fix: Replace the faulty fuel injector. On direct injection engines, it's also critical to replace the Teflon seal on the injector tip using a special tool. It is often recommended to replace all injectors on the same bank, especially on higher mileage vehicles, to ensure balanced performance.
   Est. part cost: $60-$180 per injector for an OEM part like ACDelco.
3. Corroded or Loose Injector Connector ⚪ Low Probability
   How to confirm: Unplug the connector at the cylinder 1 fuel injector and inspect the pins for corrosion, moisture, or damage. Ensure the connector clicks securely into place and that the locking tab isn't broken. Wiggle the connector with the engine running to see if it affects the misfire.
   Typical fix: Clean the connector terminals with electrical contact cleaner. If the connector or its internal pins are damaged, it will need to be replaced with a new pigtail connector (e.g., ACDelco PT2798).
   Est. part cost: $15-$40 for a new pigtail connector.

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is the least likely cause. The internal driver circuit for the injector can fail, but all other possibilities, especially wiring and the injector itself, must be exhaustively ruled out first before condemning the ECM. A failed driver will typically show no voltage or a constant ground on the control wire. Replacement can be costly, often ranging from $827 to $880 for a Buick LaCrosse.

Diagnosis Steps

1. Scan the vehicle for all stored trouble codes. Note any other injector or misfire codes, as multiple codes strongly point to a harness issue.
2. Perform a detailed visual inspection of the fuel injector wiring harness, focusing on the areas identified in TSB PIP4924D: against the intake plenum, near valve cover bolts, and against fuel lines. Use a flashlight and mirror. Feel the harness for any rough or sharp spots on the engine it might be touching.
3. If no visible damage is found, disconnect the harness from the cylinder 1 injector. Check for battery voltage on the power wire with the key on, engine off.
4. Use a 'noid light' to test for a pulse signal from the ECM on the control wire terminal while cranking the engine. A flashing light indicates the ECM is commanding the injector to fire. No light or a very dim light suggests a wiring or ECM issue.
5. If the pulse is weak or absent, check the control wire for a short to ground. Disconnect the ECM and injector connectors and check for continuity between the control wire pin at the injector connector and a good chassis ground. There should be no continuity (infinite resistance).
6. If the pulse is present and bright, suspect the injector. Swap the cylinder 1 injector with one from another cylinder (e.g., cylinder 3). If the code moves to P0267 (Cylinder 3), the injector is confirmed bad.
7. If the wiring and injector are confirmed to be good, the issue may be with the ECM's internal injector driver, which is the least common cause.

Parts You'll Likely Need

• Fuel Injector Wiring Harness Repair Kit or Pigtail — Due to the high probability of a chafed wire as per TSB PIP4924D, repairing the harness is a very common fix. A pigtail is used if the connector itself is damaged.
  Trusted brands: ACDelco, Dorman
  OEM price range: $25-$50
  Aftermarket price range: $10-$30
• Fuel Injector (OEM #ACDelco 12669384 (or 217-3034, check VIN for exact fitment)) — If the injector's internal coil has failed (shorted or open), it will need to be replaced. This is the second most common failure part for this code.
  Trusted brands: ACDelco, Bosch, Delphi
  OEM price range: $100-$180
  Aftermarket price range: $50-$120
• Fuel Injector Harness (Bank) (OEM #12621095 (Left/Bank 2), 12621096 (Right/Bank 1)) — If wiring damage is extensive and affects multiple cylinders on one bank, replacing the entire harness section is a more robust and reliable repair than multiple splices.
  Trusted brands: GM Genuine Parts
  OEM price range: $100-$160

Related Codes That Often Appear With This One

• P0301 — P0301 means "Cylinder 1 Misfire Detected." Since P0261 indicates a problem with the cylinder 1 injector circuit, that cylinder isn't getting the proper amount of fuel, which directly causes a misfire.
• P0201, P0202, P0264, etc. — If the wiring harness is chafing, it can damage multiple injector wires at once, leading to multiple injector circuit codes for different cylinders appearing simultaneously.
• P2178, P2189 — These are 'Fuel Trim Rich' or 'Fuel Trim Lean' codes. An injector that is not firing (P0261) will cause the oxygen sensor to see a lot of unburned oxygen, which the ECM interprets as a lean condition, potentially setting a lean trim code for that bank.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: SES Light And Misfire With Injector Codes. Advises technicians to inspect the fuel injector wiring harness for rubbing against the intake plenum, valve cover bolts, or fuel lines. This TSB lists a wide range of GM vehicles and engines affected by this same issue.

Platform-Specific Known Issues

• TSB PIP4924D - The Primary Culprit: TSB PIP4924D documents a widespread issue across many GM vehicles with 3.0L and 3.6L V6 engines, including the 2009-2014 LaCrosse, where the fuel injector wiring harness can rub through on engine components, causing shorts or open circuits and triggering various injector codes like P0261. Specific chafe points to inspect are against the intake plenum, a

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance (2009-2011 3.6L LLT Engine) — expected: 1.5 - 1.6 Ohms. Failure: A reading of 0 Ohms (short), OL (open), or significantly outside the specified range indicates a failed injector.
• Fuel Injector Coil Resistance (2012-2014 3.6L LFX Engine) — expected: 1.9 - 2.3 Ohms at 68°F (20°C). Failure: A reading outside this range indicates a faulty injector coil.
• Injector Control Circuit to Ground — expected: OL / Infinite Resistance. Failure: Any reading less than infinite resistance indicates a short to ground in the wiring harness or a shorted injector. This is a primary test for a 'Circuit Low' code.
• Injector Pulse Voltage (Control Wire) — expected: A high voltage pulse (50-90V) commanded by the ECM.. Failure: A standard noid light may not work correctly on GDI systems; a lab scope is the definitive tool to verify the pulse. A 'Circuit Low' code suggests the ECM detected this pulse was immediately shorted to ground.

Scan Tool Commands That Help

• GDS2 (GM Tech Tool): Cylinder Power Balance / Injector Test — Used to confirm which cylinder is not contributing. The tool deactivates one cylinder at a time and measures the RPM drop. A cylinder with a small or no RPM drop is the non-working cylinder, which should correspond to the P0261 code (Cylinder 1).
• GDS2 (GM Tech Tool): Fuel Injector Balance Test — This test fires each injector and measures the corresponding drop in fuel rail pressure. While P0261 is an electrical code, this test can help verify injector mechanical function after the circuit is repaired.
• GDS2 (GM Tech Tool): Injector Flow Rate Programming — CRITICAL STEP: When a direct injection (SIDI) fuel injector is replaced on these engines, the flow rate information from the new injector must be programmed into the ECM. Failure to do this will result in incorrect fuel delivery, poor performance, and other trouble codes, even if the P0261 is resolved.

Wiring & Ground Locations

• Cylinder 1 Injector Control Wire — On the 3.6L LFX engine, this is typically found at Pin 52 of the X1 connector at the Engine Control Module (ECM).. This is the specific pin to test for shorts to ground or continuity back to the injector connector, allowing for precise diagnosis of the circuit without tearing the entire harness apart.
• G107 — A primary engine ground located on the rear of the left (Bank 2) cylinder head.. The injector harness for Bank 2 (which includes Cylinder 1 on some transverse applications, though typically Cyl 1 is Bank 1) relies on this ground. A loose or corroded G107 can cause erratic voltage and phantom electrical codes for multiple components on that side of the engine, including injectors.
• Underhood Fuse Block — Located at the right front strut tower.. This block contains the fuses (e.g., 'INJ 1', 'INJ 2') and relays (e.g., 'PWR/TRN') that supply power to the ECM and the injector circuits. A fault here could interrupt power to the entire injector system.

Real Owner Repair Stories

• Acadia Forum User (2012 GMC Acadia with 3.6L V6 (LFX engine, shared with LaCrosse)) — Rough running, Check Engine Light with multiple injector circuit codes (P0261, P0267, P0273).
  ❌ Tried (didn't work) Swapping fuel injectors between cylinders; the codes did not follow the injectors.
  ✅ What actually fixed it A deep inspection revealed the wiring harness had chafed through on a sharp edge at the back of the cylinder head near the firewall. The user repaired the broken wires with solder and heat shrink, which resolved all codes. This strongly validates the issue described in TSB PIP4924D.
• GM-Trucks Forum User (Chevrolet Colorado with 3.6L V6) — Persistent P0261 code.
  ❌ Tried (didn't work) A repair shop replaced the fuel injector, but the code returned.
  ✅ What actually fixed it The owner found a chafed wire in the harness right near the cylinder 1 injector connector where it was rubbing against the fuel rail. Repairing this small section of wire solved the problem.

OEM Part Supersession History

• 12638530 → 12669384 — Updated part design for the 3.6L LFX engine.
  Heads up: Part number 12638530 is for the earlier LLT engine (2009-2011), while 12669384 is for the LFX engine (2012-2014). These injectors are not interchangeable due to different electrical resistance and physical design.

Model Year Variations Within This Range

• 2009-2011: These models primarily used the 3.0L LF1 and 3.6L LLT V6 engines. The LLT uses a Bosch ECM and fuel injectors (PN 12638530) with a resistance of ~1.5-1.6 Ohms.
• 2012-2014: These models used the updated 3.6L LFX V6. The LFX features a Delphi ECM, integrated exhaust manifolds, and different fuel injectors (PN 12669384) with a resistance of ~1.9-2.3 Ohms. Parts, especially injectors and wiring, are generally not interchangeable between LLT and LFX engines.