P2155 on 2010-2014 GMC Terrain: Fuel Injector Circuit Fault Causes and Fixes

What's Unique About the 2010-2014 Gmc TERRAIN

For this generation of GMC Terrain, particularly those with the 3.0L (LF1) and 3.6L (LFX) V6 engines, the fuel injector wiring harness is a known weak point. General Motors issued a Technical Service Bulletin (TSB #PIP4924D) specifically highlighting that the harness is prone to rubbing through its insulation or having internal wire breaks. Common chafe points are against the intake plenum, valve cover bolts, fuel lines, and on the side of the cylinder head under the plenum. A particularly notorious, hidden chafe point is against a metal tab on the EGR valve gasket. This issue is so common that inspecting the harness is the first step 🎬 Watch: How to diagnose a fuel injector circuit malfunction. recommended by the manufacturer when this code appears.

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 (CEL) is on
• Rough or shaking idle
• Engine misfires, which may trigger other codes like P0300
• Noticeable loss of power, especially during acceleration or climbing hills
• Poor fuel economy
• Engine may be hard to start or may not start at all
• Engine may hesitate or stumble under load

Most Likely Causes

1. Fuel Injector Wiring Harness Chafing or Damage 🔴 High Probability → Shop Engine Wiring Harness As documented in TSB #PIP4924D, the harness routing on these engines makes it susceptible to rubbing against engine components like the intake plenum, valve cover bolts, or fuel lines, leading to shorts or open circuits. A specific documented chafe point is the metal tab on the EGR valve gasket. This is the most common cause by a significant margin.
   How to confirm: Visually inspect the entire fuel injector wiring harness, paying close attention to points of contact with the engine, especially under the intake plenum and at the EGR valve gasket tab. Check for exposed wires, breaks, or rub marks. Use a multimeter to check for continuity from the PCM connector to the injector connectors. A resistance reading over 0.5 ohms on the wiring indicates a problem.
   Typical fix: Repair the damaged section of the wire using solder and heat-shrink tubing, or replace the connector pigtail if damage is near the end. If the damage is extensive, replace the entire fuel injector wiring harness (e.g., GM Part #12621095, which supersedes #12614941). Ensure the repaired or new harness is properly routed and secured away from sharp edges or hot surfaces. If chafing occurred at the EGR gasket, bend the tab over to prevent recurrence.
   Est. part cost: $50-$350
2. Faulty Fuel Injector 🟡 Medium Probability → Shop Fuel Injector
   How to confirm: After confirming the wiring is intact, unplug the suspect injector and measure the resistance (ohms) across its two electrical terminals. The expected value depends on the engine: for the 3.0L LF1 V6 (2010-2012), expect ~12 ohms; for the 3.6L LFX V6 (2013-2014), expect 1.2-1.8 ohms. An open circuit (infinite resistance) or a reading far outside the specification indicates a failed injector.
   Typical fix: Replace the faulty fuel injector. It is often recommended to replace injectors as a set to ensure balanced performance, though not strictly necessary. The OEM part for the V6 engines is often ACDelco #12634126.
   Est. part cost: $70-$150 per injector
3. Loose or Corroded Electrical Connector ⚪ Low Probability
   How to confirm: Inspect the electrical connectors at the fuel injectors and at the PCM. Look for bent pins, corrosion, or a connector that isn't fully seated. Pay close attention to the large connector on the driver's side valve cover, which is a known trouble spot.
   Typical fix: Clean the corroded terminals with an electrical contact cleaner and apply dielectric grease before ensuring the connector is securely fastened. Replace the connector pigtail (e.g., ACDelco #PT2160) if it is damaged.
   Est. part cost: $10-$40

Rare But Worth Checking

• Powertrain Control Module (PCM) Failure: → Shop Engine Control Module (ECM) This is the least likely cause. The PCM's internal driver for the injector group can fail, but all wiring and injectors should be thoroughly tested before considering PCM replacement.

Diagnosis Steps

1. Use an OBD-II scanner to confirm P2155 is present and check for any other related codes.
2. Perform a detailed visual inspection of the fuel injector wiring harness, focusing on the areas mentioned in TSB #PIP4924D: against the intake plenum, at valve cover bolts, and near fuel lines. Pay special attention to the harness near the EGR valve gasket tab.
3. If damage is found, repair the wiring. Clear the codes and test drive to see if the code returns.
4. If no wiring damage is visible, disconnect the Group D injector connectors (cylinders 2, 4, 6) and check for continuity and shorts to ground on the harness using a multimeter. Test from the ECM connector pins for each injector to isolate the fault.
5. If the harness tests good, measure the resistance of each fuel injector in the group. Compare the reading to the OEM specification (approx. 12 ohms for 3.0L, 1.2-1.8 ohms for 3.6L). Replace any injector that is out of spec.
6. Check connectors for corrosion or loose pins, especially the main harness connector on the driver's side valve cover.
7. If both the wiring and injectors test good, the issue may be with the PCM's injector driver circuit, which may require professional diagnosis.

Parts You'll Likely Need

• Fuel Injector Wiring Harness (OEM #12621095) — This is the most common failure point for this code on this vehicle, as documented by a GM TSB.
  Trusted brands: ACDelco, Dorman
  OEM price range: $200-$350
  Aftermarket price range: $100-$250
• Fuel Injector (OEM #12634126) — If the wiring harness is intact, the injector itself may have failed internally.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $120-$200
  Aftermarket price range: $70-$150
• Fuel Injector Connector Pigtail (OEM #PT2160) — If damage is localized to the connector itself, a pigtail repair is a cost-effective alternative to replacing the entire harness.
  Trusted brands: ACDelco, Dorman, Standard Motor Products
  OEM price range: $25-$40
  Aftermarket price range: $10-$25

Related Codes That Often Appear With This One

• P2146 — Relates to Fuel Injector Group 'A' and often appears with other injector group codes when a wiring harness issue is present.
• P2149 — Relates to Fuel Injector Group 'B' and can be triggered by the same faulty wiring harness affecting multiple injector circuits. On V6 models, this often refers to the same bank of injectors as P2155.
• P2152 — Relates to Fuel Injector Group 'C' and can be triggered by the same faulty wiring harness affecting multiple injector circuits.
• P0300-P0306 — These are random or specific cylinder misfire codes that are a direct symptom of the fuel injector not firing due to the P2155 circuit fault.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Addresses SES light and misfires with various injector codes including P2155, recommending inspection of the fuel injector wiring harness for damage. This TSB applies to a wide range of GM vehicles from 2009-2014 with 3.0L and 3.6L V6 engines.

Platform-Specific Known Issues

• TSB #PIP4924D specifically calls out the fuel injector wiring harness for potential rub-through or internal wire opens on 2010-2014 GMC Terrain models with V6 engines. Common chafe points are against the intake, valve covers, and fuel lines.
• Owner forums frequently cite finding the harness chafed through on the side of the cylinder head, underneath the intake plenum, requiring removal of the plenum for access and repair.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance (2013-2014 3.6L LFX V6) — expected: 1.2 - 1.8 Ohms. Failure: A reading outside this range, or an open/infinite reading, indicates a failed injector.
• Fuel Injector Coil Resistance (2010-2012 3.0L LF1 V6) — expected: Approximately 12 Ohms. Failure: A significant deviation from 12 Ohms, or an open/infinite reading, indicates a failed injector.
• Injector Circuit Voltage (Key On) — expected: 11.5 - 12.5 Volts. Failure: Voltage below 10V at the injector's power lead (measured to ground) indicates an upstream wiring or module issue.
• Injector Wiring Harness Resistance — expected: Less than 0.5 Ohms. Failure: A resistance reading greater than 0.5 Ohms when testing a wire from the ECM connector to the injector connector indicates high resistance in the harness.

Scan Tool Commands That Help

• GM GDS2 (Global Diagnostic System 2): Fuel Injector Balance Test — After confirming wiring integrity, this test can identify a poorly performing injector without removing it from the engine. The tool precisely pulses each injector and measures the corresponding drop in fuel rail pressure, allowing for a comparative analysis of injector performance.
• GM GDS2 (Global Diagnostic System 2): Output Control > Fuel Injector Control — This bidirectional function allows a technician to command individual injectors on or off to confirm if the ECM driver and the basic circuit are capable of functioning. It helps isolate whether the fault is constant or intermittent.

Wiring & Ground Locations

• Injector Group D — Cylinders 2, 4, and 6 (the front bank of cylinders, closer to the radiator).. This identifies the specific cylinders that will be disabled by the ECM when code P2155 is set, helping to focus diagnostic efforts on the correct wiring harness and injectors.
• Known Chafe Point — The metal tab on the EGR valve gasket.. This is a specific, documented failure point where the fuel injector wiring harness can rub through, causing a short or open circuit that triggers P2155. This spot is often overlooked during a general visual inspection.
• ECM Connector X1 (3.6L LFX) — At the Engine Control Module, located in the engine bay.. Allows for testing injector circuits directly at the source. For example, Injector 2 is tested at pins 75/51, and Injector 4 is at pins 74/50. Testing continuity and for shorts to ground at these pins can definitively separate a wiring harness problem from an internal ECM failure.
• ECM Connector X1 (3.0L LF1) — At the Engine Control Module, located in the engine bay.. Allows for testing injector circuits at the ECM. For example, the control circuit for Injector 2 is at Pin 37. A technician must consult the vehicle-specific wiring diagram to get the corresponding supply voltage pin for the group to perform a complete test.
• G103 / G105 — G103 is in the left front of the engine compartment. G105 is at the rear of the engine compartment on the instrument panel bulkhead.. These are critical engine and ECM ground points. A loose or corroded connection at these locations can cause erratic voltage and unpredictable electrical faults, including injector circuit codes like P2155.

Real Owner Repair Stories

• GM Preliminary Information Bulletin (documented for Chevrolet Traverse) (2009-2014 GM platform mates (incl. GMC Terrain) with 3.6L V6 engine) — Engine misfire, rough running, and multiple injector group DTCs including P2155.
  ❌ Tried (didn't work) Replacing fuel injectors, Replacing the Engine Control Module (ECM) without exhaustive wiring checks
  ✅ What actually fixed it The fuel injector wiring harness was found chafed through on a sharp metal tab of the EGR valve gasket. The successful repair involved repairing the damaged wires and bending the EGR gasket tab over to create clearance and prevent the problem from recurring.

OEM Part Supersession History

• 12614941 → 12621095 — Updated part for the driver-side (Bank 2 - front) fuel injector wiring harness.

Model Year Variations Within This Range

• 2010-2012: These models primarily used the 3.0L LF1 V6 engine. This engine uses high-impedance fuel injectors with a resistance of approximately 12 Ohms. Using the wrong resistance specification during diagnosis will lead to incorrect conclusions.
• 2013-2014: These models used the 3.6L LFX V6 engine. This engine uses low-impedance, direct-injection fuel injectors with a resistance between 1.2 and 1.8 Ohms. The harness routing and specific chafe points may also differ slightly from the 3.0L engine.