P0271 on 2010-2014 GMC Terrain: Cylinder 4 Injector Circuit High Causes and Fixes

What's Unique About the 2010-2014 Gmc TERRAIN

For the first-generation GMC Terrain (and its platform-mate, the Chevrolet Equinox), a key vulnerability is the fuel injector wiring harness. A General Motors Technical Service Bulletin (TSB #PIP4924D) specifically points to the potential for this harness to rub or chafe against engine components like the ECM bracket or the cylinder head, leading to electrical faults like a short-to-voltage that triggers P0271. While a failed injector is always possible, this known wiring issue makes a thorough inspection of the harness a critical first step on these vehicles before replacing any parts.

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
• Rough or unstable idle
• Engine misfire, which may feel like a stumble or hesitation
• Reduced engine power and poor acceleration
• Decreased fuel economy
• Noticeable fuel smell from the exhaust if the injector is stuck open

Most Likely Causes

1. Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness A manufacturer TSB (#PIP4924D) specifically calls out inspecting the fuel injector wiring harness for damage on these vehicles, indicating it's a known failure point. The harness can rub against the engine or brackets, causing a short to voltage.
   How to confirm: Visually inspect the wiring harness leading to the cylinder 4 fuel injector. Look for any signs of rubbing, chafing, melted plastic, or exposed wires, particularly where the harness might contact the cylinder head or metal brackets near the back of the engine.
   Typical fix: If damage is found, repair the specific wires using heat-shrink butt connectors and re-secure the harness away from the contact point. If damage is near the connector, replace the pigtail.
   Est. part cost: $15-$40
2. Failed Fuel Injector 🔴 High Probability → Shop Fuel Injector The Gasoline Direct Injection (GDI) injectors on the 2.4L Ecotec engine operate under high pressure and can fail internally, causing an electrical short or open circuit.
   How to confirm: Swap the cylinder 4 fuel injector with one from another cylinder (e.g., cylinder 1). Clear the codes and drive the vehicle. If the code changes to P0262 (Cylinder 1 Injector Circuit High), the injector is faulty. Alternatively, use a multimeter to check the resistance of the injector. A good GDI injector for this engine should have a resistance between 1.1 and 2.0 ohms. A reading of 0 ohms or infinite (OL) indicates a bad injector.
   Typical fix: Replace the faulty fuel injector. It is often recommended to replace all injectors at the same time, especially on higher mileage vehicles.
   Est. part cost: $50-$150
3. Corroded or Loose Injector Connector 🟡 Medium Probability
   How to confirm: Unplug the connector at the cylinder 4 injector and inspect the pins on both the injector and the connector for corrosion (green or white powder) or damage. Ensure the connector clicks securely into place.
   Typical fix: Clean the connector pins with an electrical contact cleaner or replace the connector if it's damaged.
   Est. part cost: $15-$40

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 and get stuck 'on', causing a high voltage reading. However, all other possibilities (wiring, injector) should be exhaustively ruled out before considering PCM replacement, as it is expensive and requires programming.

Diagnosis Steps

1. Read the code from the OBD-II port using a scanner and confirm P0271 is present. Note any other codes, especially P0304.
2. Visually inspect the wiring harness and connector for the cylinder 4 fuel injector. Pay close attention to areas where the harness may rub against other parts, as noted in TSB #PIP4924D.
3. Disconnect the injector and check for corrosion or damage to the connector pins.
4. If the visual inspection is clear, swap the cylinder 4 injector with another cylinder's injector (e.g., cylinder 1).
5. Clear the codes and start the engine. Let it run for a few minutes.
6. Re-scan for codes. If the code has moved to the other cylinder (e.g., P0262 for cylinder 1), the fuel injector is the problem and must be replaced.
7. If the P0271 code returns, the issue is in the wiring or the PCM. Use a multimeter to check the resistance of the injector itself. It should be between 1.1 and 2.0 ohms for the 2.4L GDI engine. If it's out of spec, replace the injector.
8. If the injector tests good, use a noid light or multimeter to verify the electrical signal at the injector connector. A 'circuit high' code suggests you may find constant battery voltage on the control wire when there should be a pulsing ground.
9. If the signal is incorrect, check the wiring for continuity and for shorts between the PCM and the injector connector. Repair any open or shorted wires.
10. If the wiring and injector are confirmed to be good, the PCM is the likely culprit.

Parts You'll Likely Need

• Fuel Injector (2.4L GDI) (OEM #12633789) — This is the most common part to fail that causes a P0271 code, after ruling out wiring issues.
  Trusted brands: ACDelco (GM Genuine), Hitachi, Standard Motor Products
  OEM price range: $90-$150
  Aftermarket price range: $50-$100
• Fuel Injector Connector Pigtail (OEM #88862303 (ACDelco PT2183)) — If the wiring harness is damaged near the connector, replacing the pigtail is the standard repair. Dorman 645-207 is a common aftermarket equivalent.
  Trusted brands: ACDelco, Dorman
  OEM price range: $25-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0304 — P0304 indicates a 'Cylinder 4 Misfire.' Since a faulty injector circuit prevents proper fueling for that cylinder, a misfire is a direct consequence.
🎬 See this video for a deeper look at P0304 misfires.
• P0204 — P0204 is a more general 'Injector Circuit/Open - Cylinder 4' code. It can appear alongside P0271 as the ECM tries to diagnose the electrical fault.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Mentions that codes including P0271 can be set due to a fuel injector wiring harness issue, prompting an inspection for chafing or internal wire opens.

Platform-Specific Known Issues

• A known issue documented in TSB #PIP4924D involves the fuel injector wiring harness chafing or rubbing against the cylinder head or brackets, causing shorts or open circuits that can trigger this code.
• The 2.4L Ecotec engine is also known for high oil consumption and timing chain issues, but these are generally unrelated to a specific injector circuit code like P0271.

Mechanic-Grade Diagnostic Values

• Low-Side Fuel Pressure (Key On, Engine Off) — expected: 345-690 kPa (50-100 psi). Failure: Pressure below this range indicates a weak in-tank fuel pump.
• High-Side Fuel Pressure (Engine Idling) — expected: 1.9-5.0 MPa (276-725 PSI). Failure: Pressure significantly outside this range can indicate a failing High Pressure Fuel Pump (HPFP) or sensor issue.
• Injector Connector Voltage (Key On, Engine Off) — expected: Power Wire: ~12V (Battery Voltage). Control Wire: ~0V.. Failure: For a P0271 'Circuit High' code, finding constant voltage on the control wire indicates a short to power in the harness.
• Fuel Injector Resistance (GDI) — expected: 1.1 - 2.0 ohms (Pass 2 data). Some sources for similar engines cite 11-15 ohms, which is more typical of PFI injectors. GDI values are typically lower.. Failure: A reading of 0 ohms (short) or infinite/OL (open) indicates a failed injector.
• Long-Term Fuel Trim (LTFT) — expected: Within +/- 10%. Failure: A highly negative LTFT on Bank 1 could indicate an injector is stuck open or leaking, causing the ECM to pull fuel. A highly positive LTFT could occur if the injector isn't firing, causing a lean condition.

Scan Tool Commands That Help

• GDS2, Autel, XTOOL, Snap-on, etc.: Cylinder Power Balance / Fuel Injector Balance — This is a primary diagnostic test. The tool disables each injector one by one and measures the drop in RPM or fuel pressure. If disabling cylinder 4 causes little or no change compared to other cylinders, it confirms cylinder 4 is not contributing power, pointing to a fault in its fuel or ignition system.
• GDS2, Autel, XTOOL, etc.: Fuel Pump Enable — Used to turn on the in-tank (low pressure) fuel pump without the engine running. This allows for safe and accurate testing of the low-side fuel pressure to rule out a weak in-tank pump.

Wiring & Ground Locations

• G112 — On the lower left (driver's side) front of the 2.4L engine block.. This is a primary engine and powertrain ground. A loose or corroded connection here can create a voltage offset and cause erratic behavior in sensor and actuator circuits, potentially triggering false injector circuit codes.
• ECM Connector X1 — The Engine Control Module (ECM) is in the driver's side of the engine bay. X1 is one of its main connectors.. The control wires for the fuel injectors run from this connector. TSBs point to this harness chafing on the ECM bracket. Based on similar GM engines, the cylinder 4 injector wires are likely at pins 50 and 74 of this connector, making it a key test point for continuity and shorts.

Real Owner Repair Stories

• ScannerDanner.com Forum User (2012 Chevy Equinox 2.4L (platform mate)) — Rich condition, stalling at stops, various fuel pressure codes.
  ❌ Tried (didn't work) Initial diagnosis pointed to a faulty fuel rail pressure sensor, but replacement did not fix the issue.
  ✅ What actually fixed it The vehicle had an aftermarket High Pressure Fuel Pump (HPFP) installed. At idle, the ECM commanded 0 PSI, but the aftermarket pump would only drop to 290 PSI, flooding the engine. Replacing the aftermarket HPFP with an OEM unit resolved the issue, as the OEM pump correctly dropped pressure to ~70 PSI when commanded.
• YouTube User 'flexbone' (2012 GMC Terrain) — Check Engine Light with codes P219A (Bank 1 Air-Fuel Ratio Imbalance) and P0300 (Random Misfire).
  ❌ Tried (didn't work) The owner noted that the ignition coils and VVT solenoids had already been replaced, likely in a previous attempt to fix the misfire.
  ✅ What actually fixed it After performing an injector test, it was determined that several fuel injectors were faulty. Replacing the bad fuel injectors resolved the codes and rough running condition.

Model Year Variations Within This Range

• 2010-2014: The 2.4L Ecotec engine was updated mid-generation. 2010-2011 models typically have the LAF engine. 2012-2014 models have the LEA engine, which is FlexFuel (E85) compatible. While they are both GDI and share the same core design, fuel system components like injectors may have different part numbers and are not necessarily interchangeable. Always verify parts by VIN.