P2149 on 2010-2014 GMC Terrain: Fuel Injector Group B Circuit Causes and Fixes

What's Unique About the 2010-2014 Gmc TERRAIN

This generation of GMC Terrain, along with its sibling the Chevrolet Equinox, is highly susceptible to a specific wiring issue. GM issued Technical Service Bulletin #PIP4924D, which directly addresses code P2149 and other related injector codes. The bulletin points to the fuel injector wiring harness rubbing against engine components, particularly the sharp edges of the ECM/TCM bracket, causing wires to break and creating an open circuit. This makes a harness inspection the number one diagnostic step, ahead of replacing any components. This chafing issue is a well-documented problem across many GM platforms.

Diagnostic Flowchart

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

Symptoms You May Notice

• Engine running very rough or shaking
• Noticeable loss of engine power
• Flashing Check Engine Light
• Engine may stall or be difficult to start
• Audible engine misfires or popping sounds
• Hesitation when accelerating

Most Likely Causes

1. Chafed or Broken Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As documented in GM TSB #PIP4924D, the wiring harness routing can cause it to rub against sharp edges on the engine or brackets, eventually wearing through the insulation and breaking the copper wire. Common chafe points include the ECM/TCM bracket, the driver's side upper control arm, and the shock tower. Engine vibration and movement from shifting between drive and reverse can exacerbate the issue.
   How to confirm: Visually inspect the entire fuel injector wiring harness, focusing on where it runs over the top of the engine and near brackets. Pay extremely close attention to the area where the harness may contact the metal ECM/TCM bracket. Gently pull on the individual wires near the injector connectors for cylinders 2 and 3 (on the 2.4L); a broken wire inside the insulation may stretch or come apart completely. The break is often found within a few inches of an injector connector.
   Typical fix: Repair the broken wire(s) using solder and heat-shrink tubing or a quality butt connector. If the break is very close to the connector, a new 'pigtail' connector may need to be spliced in. After the repair, secure the harness with a protective wire loom and zip ties to prevent it from rubbing in the same spot again. Rerouting the harness slightly away from the sharp edge is critical.
   Est. part cost: $5-$35

Rare But Worth Checking

• Faulty Fuel Injector: → Shop Fuel Injector While a single injector can fail electrically (open circuit), it is rare for multiple injectors in the same group to fail simultaneously. This should be considered only after the wiring harness has been thoroughly inspected and cleared of any faults. An injector's resistance can be tested with a multimeter; a healthy one should typically read between 11-14 ohms.
• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) A failed injector driver circuit inside the PCM is very rare. The PCM should only be suspected after all wiring and fuel injectors have been tested and confirmed to be working correctly. This is the least likely cause.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner 🎬 See this guide to locate the fuel injector fuse and relay. and note all active codes.
2. Begin with a thorough visual inspection of the fuel injector wiring harness, as recommended by TSB #PIP4924D. Focus on known chafe points: the ECM/TCM bracket, upper control arm, and shock tower.
3. Gently tug on the wires at the connectors for injectors 2 and 3 (on the 2.4L engine). A broken wire inside the insulation will often stretch or break completely. This is a very common finding.
4. If no visible damage is found, use a NOID light at the injector connector to verify if the PCM is sending a pulse signal. No pulse points to a wiring or PCM issue.
5. If a NOID light is unavailable, use a multimeter to check for continuity on the supply and control wires from the PCM connector to the injector connectors. Resistance greater than 0.2 Ω indicates a problem.
6. If wiring continuity is confirmed, check the resistance of the fuel injectors in Group B. A healthy injector will typically have a resistance between 11-14 ohms. A reading of infinity (OL) indicates a failed, open injector.
🎬 Watch: A helpful walkthrough for diagnosing and replacing a faulty injector.
7. If both the wiring and injectors test good, the issue may be with the PCM, but this is extremely unlikely and should be the last resort.

Parts You'll Likely Need

• Fuel Injector (OEM #12633789) — Only needed if an injector is confirmed to be electrically faulty (open circuit) after the wiring harness has been ruled out as the cause.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $110-$140
  Aftermarket price range: $50-$100
• Fuel Injector Connector Pigtail — Necessary if the wire break is too close to the original connector to allow for a simple splice repair. Allows for a fresh connector and length of wire to be spliced into the main harness.
  Trusted brands: ACDelco, Dorman, Standard Motor Products (S-2081)
  OEM price range: $20-$40
  Aftermarket price range: $10-$25
• Wire Loom/Conduit — Used to protect the repaired wiring harness from future chafing and damage. This is a critical part of a lasting repair.
  Trusted brands: Dorman
  OEM price range: $5-$15
  Aftermarket price range: $5-$15

Related Codes That Often Appear With This One

• P2146 — This code is for 'Fuel Injector Group A Supply Voltage Circuit/Open'. If both P2146 and P2149 are present, it strongly suggests a wiring harness issue at a point common to both circuits, reinforcing the diagnosis of a chafed harness.
• P0201, P0202, P0203, P0204 — These are specific codes for injector circuit malfunctions for individual cylinders. They can appear alongside P2149 and are also mentioned in TSB #PIP4924D as being related to the same wiring harness problem.

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #PIP4924D: Advises technicians to inspect the fuel injector wiring harness for rubbing or internal wire opens when encountering a list of diagnostic trouble codes including P2149.
• Bulletin #21-NA-149: While for newer GM models, this TSB details similar engine wiring harness chafing issues against components like the ECM bracket and control arms, providing excellent visual context for the type of failure common on the Terrain.

Platform-Specific Known Issues

• A well-documented issue, covered by GM Technical Service Bulletin #PIP4924D, involves the fuel injector wiring harness rubbing through on engine components, causing an open circuit that triggers codes like P2149.
• Owner Repair Experience: Owners on forums like terrainforum.net frequently report finding a broken wire for the #2 or #3 injector, often with no visible external damage to the insulation. The fix is almost always to cut out the bad section, splice in a new piece of wire, and protect the harness with extra loom and zip ties to keep it away from the bracket it was rubbing on.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance — expected: 11-14 Ohms. Failure: A reading of zero or infinity (OL) indicates a failed injector coil.
• Injector Supply Voltage — expected: 11.5–12.5 Volts with engine at ~2,000 RPM. Failure: Voltage below 9V indicates a problem in the supply circuit.
• Wiring Harness Continuity — expected: Less than 0.2 Ohms. Failure: Resistance greater than 0.2 Ω from the ECM output pin to the injector connector suggests a high-resistance path due to corrosion or a damaged wire.
• Injector Balance Test (Max Difference) — expected: Less than 20 kPa. Failure: A pressure difference greater than 20 kPa between injectors indicates one or more faulty (rich or lean) injectors.

Scan Tool Commands That Help

• GDS2 / Tech 2: Injector Balance Test — To functionally test and compare the flow rate of each injector by measuring fuel rail pressure drops. This can identify a clogged or faulty injector that might pass a simple resistance test.
• GDS2 / Tech 2: Cylinder Cut-Out / Injector Disable — Allows a technician to disable one cylinder at a time to determine which one is causing a misfire. If disabling a cylinder causes no change in engine RPM or sound, that is the cylinder with the problem.

Wiring & Ground Locations

• Engine Harness Grounds — On the 3.6L V6, there are typically three smaller ground connections on the engine block, often on the back or side, and one large ground from the battery to the engine block, near the starter.. A poor or corroded engine ground can cause a variety of electrical issues, including fluctuating voltage references for sensors and actuators like fuel injectors, potentially triggering circuit codes.
• Injector Harness Connector (X104) — Location can vary, but on many GM engines it is a main connector where the fuel injector sub-harness joins the main engine harness.. This connector is a potential point of failure. A loose or corroded pin within this connector could affect the entire Group B injector circuit.
• ECM Connectors (X1/X2) — The Engine Control Module (ECM) is typically located in the engine bay. The injector circuits will originate from pins on one of its main connectors.. When diagnosing a persistent open circuit, a technician may need to test for continuity directly from the specific pin at the ECM connector to the pin at the fuel injector connector to isolate the fault.

Real Owner Repair Stories

• YouTube video comment section (2004 Silverado 2500HD LLY Duramax (platform exhibits similar failure mode)) — Engine running terribly, codes P0202 (Injector 2 Circuit) and P2149 (Group B Circuit) were present.
  ❌ Tried (didn't work) Initial diagnosis pointed to a bad injector, but further investigation revealed a wiring issue.
  ✅ What actually fixed it The wiring to injector #2 was shot. The owner spliced in a new injector connector pigtail, which resolved the issue and made the truck run 'as good as new'.

Model Year Variations Within This Range

• 2010-2012: The optional V6 engine was the 3.0L LF1.
• 2013-2014: The optional V6 engine was updated to the 3.6L LFX. While the P2149 code's meaning is the same, the physical location of injectors, harness routing, and specific chafe points may differ slightly between the 2.4L, 3.0L, and 3.6L engines.