P2149 on 2009-2014 GMC Acadia: Fuel Injector Group B Circuit Causes and Fixes

What's Unique About the 2009-2014 Gmc ACADIA

The first-generation Acadia, along with its platform mates (Buick Enclave, Chevy Traverse, Saturn Outlook), is known for having specific chafe points in the engine wiring harness. GM issued a Technical Service Bulletin (TSB PIP4924D) that directly addresses this code and points technicians to inspect the fuel injector harness for damage where it can rub against the intake manifold, valve covers, fuel lines, or the FICM (Fuel Injection Control Module) bracket. This makes a wiring fault the most probable cause, more so than a failed injector or computer.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Severe engine misfire, shaking, or vibration
• Flashing or solid Check Engine Light
• Significant loss of engine power
• Engine may stall or be difficult to start
• Rough or unstable idle
• Reduced fuel economy

Most Likely Causes

1. Chafed or Broken Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As documented in GM TSB PIP4924D, the harness routing creates several points where it can rub through against engine components. Common chafe spots are against the intake plenum, valve cover bolts, fuel lines, and the metal ECM bracket. Over time, engine vibration causes the harness insulation to wear away, leading to an open or shorted wire.
   How to confirm: Visually inspect the entire fuel injector wiring harness, paying close attention to the areas mentioned in the TSB. Perform a continuity test on the power supply wires for the Bank 2 injectors from the ECM connector to the injector connectors. A wiggle test on the harness while the engine is running (if possible) may induce the fault.
   Typical fix: Repair the broken or shorted wires using solder and heat-shrink tubing. 🎬 Watch: Learn how to repair wiring harnesses like a pro. Protect the harness from future damage using high-temperature wire loom, conduit, or re-routing. In severe cases, the entire harness section or pigtail connector may need to be replaced.
   Est. part cost: $10-$250
2. Faulty Fuel Injector 🟡 Medium Probability → Shop Fuel Injector While less common than wiring issues for this specific code, the direct injection (SIDI) injectors operate under high stress and can fail internally. A failed internal coil will create an open or short in the circuit.
   How to confirm: Measure the resistance of the injectors on Bank 2 using a multimeter. Compare the readings to the manufacturer's specifications (Note: specs differ by engine, see Model-Year Variations). An infinite or zero reading, or one that is significantly different from the others, indicates a failed injector.
   Typical fix: Replace the failed fuel injector. 🎬 Watch: Step-by-step guide to replacing GM 3.6L fuel injectors. It is often recommended to replace all injectors on the same bank or all six at the same time to ensure balanced fuel delivery.
   Est. part cost: $50-$150 per injector
3. Loose or Corroded Connector ⚪ Low Probability The injector connectors and the main ECM connectors can accumulate moisture or have pins that loosen over time due to vibration.
   How to confirm: Inspect the electrical connectors at the fuel injectors and the ECM for corrosion, moisture, or loose pins. Wiggle the harness while the engine is running (if possible) to see if the misfire changes. Disconnect the connectors and check for any green/white corrosion or backed-out pins.
   Typical fix: Clean the connectors with electrical contact cleaner and apply dielectric grease. If pins are loose, the connector pigtail may need to be replaced.
   Est. part cost: $5-$30

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is rare and should only be considered after all wiring and injector possibilities have been exhaustively ruled out. A failed internal injector driver circuit in the ECM can mimic a wiring problem.

Diagnosis Steps

1. Verify the presence of P2149 with an OBD-II scanner. Note any other codes present, especially individual misfire (P030x) or injector circuit (P020x) codes.
2. Perform a thorough visual inspection of the fuel injector wiring harness for Bank 2 (front of the engine). Focus on the known chafe points: where the harness wraps around the intake plenum, near valve cover bolts, against fuel lines, and at the metal ECM bracket.
3. If the engine can run, perform a 'wiggle test' by carefully moving sections of the harness to see if it causes the engine to stumble or the code to appear/disappear.
4. Disconnect the battery.
5. Disconnect the harness connectors for the Bank 2 fuel injectors (cylinders 2, 4, 6) and the main ECM connector.
6. Using a multimeter set to Ohms, check for continuity on the power supply wire for each injector from the ECM connector to the injector connector. An open circuit (infinite resistance) indicates a broken wire.
7. Check for a short to ground by testing for continuity between the power supply wire at the injector connector and a good chassis ground. Any reading other than infinite resistance indicates a short.
8. If wiring tests good, measure the internal resistance of each fuel injector on Bank 2. Compare the readings to OEM specifications, noting the difference between LLT and LFX engines. Replace any injector that is out of spec.
9. If both wiring and injectors test good, the fault may lie within the ECM, which requires professional diagnosis.

Parts You'll Likely Need

• Fuel Injector Wiring Harness Repair Kit/Pigtail (OEM #ACDelco PT2183 (Connector), Standard Motor Products S-1024) — This is the most common failure point. Often only the connector or a small section of wire is damaged, making a pigtail a cost-effective repair.
  Trusted brands: ACDelco, Dorman, Standard Motor Products
  OEM price range: $40-$70
  Aftermarket price range: $15-$40
• Fuel Injector (OEM #ACDelco 217-3445 (supersedes 12638530, 12611545)) — If the injector's internal coil has failed, it will need to be replaced. This is the second most likely component to fail. Note that part numbers differ for 2012+ LFX engines.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $100-$180
  Aftermarket price range: $50-$120

Related Codes That Often Appear With This One

• P2146 — This is the equivalent code for Injector Group 'A' (Bank 1). Seeing both may indicate a more widespread wiring issue, a problem at the ECM, or a fault affecting the main power feed to both banks.
• P0300 — This is a 'Random/Multiple Cylinder Misfire' code, which is a direct result of an entire bank of injectors being shut down.
• P0302, P0304, P0306 — These are misfire codes for the individual cylinders on Bank 2 (cylinders 2, 4, and 6). The ECM may log these along with the group code P2149.
• P0202, P0204, P0206 — These codes indicate a circuit malfunction for the individual injectors on Bank 2. They often accompany P2149 as the ECM identifies issues with the entire group.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Addresses a Service Engine Soon light and misfire with various injector codes (including P2149) and directs technicians to inspect the fuel injector wiring harness for rubbing or internal opens. It specifically mentions checking near the FICM bracket.

Platform-Specific Known Issues

• GM Technical Service Bulletin PIP4924D was issued for multiple vehicles including the 2009-2014 Acadia, specifically for injector-related codes including P2149 caused by wiring harness rub-through.
• Owners on forums for the Acadia and its platform mates frequently post about this exact code, with the overwhelming majority of successful repairs involving finding and fixing a chafed wire, often hidden under the intake manifold or near the front valve cover.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (2009-2011 LLT Engine) — expected: 11 - 14 Ohms. Failure: A reading significantly outside this range, or an open/short (infinite/zero ohms), indicates a failed injector.
• Fuel Injector Resistance (2012-2014 LFX Engine) — expected: 1.5 - 2.5 Ohms. Failure: A reading outside this much lower range indicates a failed injector. Using the wrong spec will lead to misdiagnosis.
• Scan Tool 'Fuel Injector Balance Test' — expected: The fuel pressure drop for each injector should be within 1.5-3.0 PSI (10-20 kPa) of the average for all other injectors.. Failure: An injector with a significantly smaller or larger pressure drop is either clogged or leaking.
• Injector Connector Voltage (Key On, Engine Off) — expected: ~12.0 Volts (Battery Voltage). Failure: Low or no voltage points to an open in the power supply wire from the ECM. This is the fault P2149 directly reports.

Scan Tool Commands That Help

• GM Tech 2 / GDS2: Fuel Injector Balance Test — Use this after confirming the wiring is intact. This command individually fires each injector and measures the fuel pressure drop, allowing a technician to identify a mechanically faulty (clogged or weak) injector without removing the intake manifold.
• GM Tech 2 / GDS2: Cylinder Power Balance / Injector Kill — This function allows the user to disable one injector at a time. If disabling an injector on the affected bank (2, 4, or 6) causes no change in how the engine runs, it helps confirm that cylinder was already dead, but it won't distinguish a wiring vs. injector fault for P2149 since the whole bank is usually shut down.

Wiring & Ground Locations

• ECM (FICM) Bracket — The Engine Control Module (ECM) is located in the engine compartment. The bracket holding it is a primary chafe point mentioned in TSB PIP4924D.. The fuel injector harness is routed near this metal bracket, and engine vibration can cause the harness to rub through, creating an open or short circuit that triggers P2149.
• G103 — On the cowl in the left rear of the engine compartment, often near or above the brake booster.. This is a major body and module ground. While not directly in the injector circuit, a poor ground here can cause unpredictable electrical issues and reference voltage problems for the ECM.
• G104 — On the left rear corner of the engine, attached to the cylinder head.. This is a primary engine ground strap. A loose or corroded connection here can cause the ECM and its sensors to have an unstable ground reference, potentially leading to incorrect fault detection.
• ECM Connector X1 — The large 73-pin main connector on the Engine Control Module.. This is the termination point for the injector circuits. Advanced diagnosis requires checking for continuity and voltage at the specific pins leading to the Bank 2 injectors. A 2012 Acadia pinout is available for reference.

Real Owner Repair Stories

• YouTube video on a 2011 Chevrolet Traverse (platform mate) (2011 Chevrolet Traverse 3.6L V6) — Check engine light with code P2149, severe misfire/rough running.
  ❌ Tried (didn't work) The technician in the video went directly to wiring diagnosis based on experience with the platform.
  ✅ What actually fixed it The technician found a section of the injector wiring harness that had chafed against a metal bracket. The wires inside were shorting together. The fix was to separate the wires, repair the insulation on the damaged sections, and protect the harness with additional conduit to prevent it from happening again.

"I Checked Everything" — The Actual Cause

• A visual inspection of the harness may show no damage, but the wire can be broken internally from vibration and stretching. This is a common point of failure on the Lambda platform. The wire often breaks right where it enters a connector or at a sharp bend. A 'wiggle test' (manipulating the harness while the engine is running or while checking continuity) is essential to find these hidden opens that a visual check or static continuity test might miss.

OEM Part Supersession History

• 12623325 (Example for 2009) → 19300016 (Example for 2009) — Standard part updates for reliability and software changes.
  Heads up: The ECM is specific to the model year and engine type (LLT vs. LFX). A 2009 ECM (e.g., 12623325) will not work in a 2012 model. The replacement ECM must be programmed to the vehicle's VIN.
• 12636355 (Example for 2010-2011) → 19300014 (Example for 2010-2011) — Standard part updates for reliability and software changes.
  Heads up: This ECM is for the LLT engine. It is not compatible with 2012+ LFX engines. Programming to the vehicle's VIN is required.

Model Year Variations Within This Range

• 2009-2011: These model years use the 3.6L LLT V6 engine. This engine uses fuel injectors with a resistance of approximately 11-14 ohms. It also features a Bosch ECM and an aluminum intake manifold.
• 2012-2014: These model years use the updated 3.6L LFX V6 engine. This engine uses different fuel injectors with a much lower resistance of approximately 1.5-2.5 ohms. It features a Delphi ECM and a composite intake manifold. Using the wrong resistance specification during diagnosis will lead to incorrect conclusions.