P0273 on 2009-2014 GMC Acadia: Cylinder 5 Injector Circuit Low Causes and Fixes

What's Unique About the 2009-2014 Gmc ACADIA

The first-generation GMC Acadia and its platform mates (Buick Enclave, Chevy Traverse) with the 3.6L V6 engine are particularly susceptible to this code due to a known issue with the fuel injector wiring harness. A General Motors Technical Service Bulletin (TSB #PIP4924D) specifically points to the harness rubbing through its protective sheathing, causing shorts or open circuits. This makes a wiring inspection a critical first step, as opposed to immediately assuming the injector itself has failed.

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 shaky idle
• Engine hesitation or stumbling during acceleration
• Reduced engine power or 'limp mode'
• Poor fuel economy
• Audible popping or tapping sound from the engine bay
• Engine may be hard to start

Most Likely Causes

1. Chafed/Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As documented in GM TSB #PIP4924D, the fuel injector wiring harness is known to rub against engine components, leading to exposed wires and short circuits. Forum users frequently report this harness chafing at the rear of the intake manifold or against the corner of the cylinder head.
   How to confirm: Visually inspect the entire fuel injector wiring harness, paying close attention to any points where it contacts the engine block, brackets, or the rear of the intake manifold. Look for worn sheathing, exposed copper, or pinch points. A common failure point is where the harness passes over the engine.
   Typical fix: Repair the damaged section of the wire using solder and heat shrink tubing, then protect the harness with new loom or by re-routing it to prevent future rubbing. Some owners use zip ties to secure the harness away from sharp edges.
   Est. part cost: $5-$25
2. Failed Cylinder 5 Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Fuel injectors can fail internally over time due to electrical faults or clogging. The direct injection (DI) system on the 3.6L LLT and LFX engines operates under high pressure, which can contribute to injector wear and carbon buildup issues.
   How to confirm: After confirming the wiring is good, perform a resistance test on the injector using a multimeter. CRITICAL: The expected resistance varies by engine. For the 2009-2011 LLT engine, expect 11.8-12.6 Ohms. For the 2012-2014 LFX engine, expect 1.2-1.8 Ohms. A reading outside the correct range for your engine indicates a bad injector. A more definitive test is to swap the cylinder 5 injector with another cylinder's injector (e.g., cylinder 3). If the code changes to P0267 (Cylinder 3 Injector Circuit Low), the injector is faulty.
   Typical fix: Replace the faulty fuel injector. It is often recommended to replace all injectors on the same bank, 🎬 See this walkthrough for intake removal and injector replacement or all six, if they are high mileage.
   Est. part cost: $50-$150
3. Poor Connection at Injector or ECM ⚪ Low Probability
   How to confirm: Disconnect and inspect the electrical connectors at both the fuel injector and the ECM. Look for corrosion, bent pins, or a loose fit. The injector connector itself can sometimes fail. Wiggle the connector with the engine running to see if it affects the idle.
   Typical fix: Clean or repair the connector. Ensure it is fully seated and the locking tab is engaged. In some cases, the injector pigtail connector may need to be replaced.
   Est. part cost: $0-$30

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is very uncommon. The ECM's internal driver for the injector circuit can fail, but this should only be considered after all wiring and the injector itself have been proven to be good.

Diagnosis Steps

1. Scan the ECM for any stored trouble codes. Note any other codes that are present.
2. Identify Cylinder 5. On the transverse-mounted 3.6L V6 engine in the Acadia, the cylinders against the firewall are the 'odd' bank (Bank 1). From passenger to driver side, they are 1-3-5. Cylinders at the front (near the radiator) are the 'even' bank (Bank 2), 2-4-6. Cylinder 5 is on the firewall side, on the driver's end of the engine.
3. Carefully perform a visual inspection of the fuel injector wiring harness, as recommended by TSB #PIP4924D. Look for any signs of rubbing, chafing, or damage, especially where the harness passes over the engine and near the rear of the intake manifold.
4. Inspect the electrical connector at the cylinder 5 fuel injector for a secure fit, corrosion, or damaged pins.
5. If no wiring damage is found, use a noid light to test for an electrical pulse at the injector connector while cranking the engine. If the light flashes, the ECM is sending a signal.
6. Turn the ignition off. Disconnect the injector and measure its internal resistance with a multimeter. For the 2009-2011 3.6L LLT engine, the resistance should be between 11.8 and 12.6 ohms. For the 2012-2014 3.6L LFX engine, it should be between 1.2 and 1.8 ohms. An open circuit (OL) or a reading outside the correct range indicates a bad injector.
7. If the injector tests good but the noid light did not flash, check for continuity and shorts in the wiring between the ECM and the injector connector.
8. As a final confirmation, consider swapping the cylinder 5 injector with one from another cylinder (e.g., cylinder 3, which is also on Bank 1). Clear the codes and run the engine. If the fault code moves to the new cylinder (P0267 for cylinder 3), the injector is confirmed to be the problem.
9. If all wiring and the injector are confirmed to be good, the issue may be with the ECM, which is a rare failure.

Parts You'll Likely Need

• Fuel Injector (OEM #12638530, superseded by 12669384) — If the wiring harness is intact, the fuel injector itself is the next most likely component to have failed internally.
  Trusted brands: ACDelco
  OEM price range: $80-$120
  Aftermarket price range: $45-$75
• Wiring Repair Supplies — Needed to fix the common issue of a chafed wiring harness, as cited in TSB PIP4924D.
  OEM price range: $5-$25
  Aftermarket price range: $5-$25
• Fuel Injector Connector Pigtail (OEM #ACDelco PT3702 (example, verify fitment)) — If the connector at the injector is damaged, corroded, or has a loose connection, replacing the pigtail may be necessary.
  Trusted brands: ACDelco, Dorman
  OEM price range: $25-$40
  Aftermarket price range: $15-$25

Related Codes That Often Appear With This One

• P0305 — P0305 indicates a misfire in cylinder 5. P0273 is a common cause for P0305, as the injector circuit fault prevents proper fueling, leading to a misfire.
• P0205 — This code indicates a general malfunction in the cylinder 5 injector control circuit. It can appear alongside P0273 and points to the same set of potential electrical issues.
• P0261, P0264, P0267, P0270, P0276 — These are the 'Circuit Low' codes for the other cylinders. If multiple injector codes are present, it strongly suggests a widespread issue like a damaged main wiring harness, as mentioned in TSB PIP4924D.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Mentions that codes like P0273 can be caused by the fuel injector wiring harness rubbing through. It advises technicians to inspect the harness for damage. The presence of multiple injector circuit codes (e.g., P0270, P0273, P0276) is a strong indication of this harness issue.

Platform-Specific Known Issues

• A known issue documented in TSB #PIP4924D involves the fuel injector wiring harness rubbing through and causing various injector circuit codes, including P0273. A thorough inspection of the harness is the most critical diagnostic step for this specific vehicle.
• Forum discussions highlight a specific chafing point where the harness passes over the rear of the intake manifold. The plastic sheathing wears away, allowing wires to short against the engine.
• Due to the transverse engine layout, accessing the rear bank of cylinders (1, 3, 5) where cylinder 5 is located requires removing the intake manifold, which adds to the labor time and complexity of replacing the injector.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance (2009-2011 3.6L LLT Engine) — expected: 11.8 - 12.6 Ohms. Failure: A reading significantly outside this range, or an open circuit (OL), indicates a failed injector.
• Fuel Injector Coil Resistance (2012-2014 3.6L LFX Engine) — expected: 1.2 - 1.8 Ohms. Failure: A reading significantly outside this range indicates a failed injector. This is the value most commonly cited for GM direct injectors.
• Scan Tool 'Fuel Injector Balance Test' Pressure Drop — expected: The pressure drop for one injector should be within 1.5 PSI (10 kPa) of the average of the other injectors.. Failure: A significantly smaller or larger pressure drop on cylinder 5 indicates a malfunctioning, clogged, or leaking injector.
• Injector Supply Voltage (at connector, Key On Engine Off) — expected: 11.5 - 12.5 Volts. Failure: Voltage below 10V points to a problem with the power supply wiring or the ECM.

Hidden / Shadow Codes Worth Checking

• Mode $06 Misfire Counters: This is not a specific trouble code, but a data parameter accessible with most advanced scan tools. It shows raw misfire counts for each cylinder before they reach the threshold to set a P030x code. It can be used to confirm if the circuit fault is causing an actual misfire. (see via Advanced OBD-II Scan Tool with Mode $06 capability.)

Scan Tool Commands That Help

• GDS2 / Tech2 (or equivalent professional scanner): Fuel Injector Balance Test — Use this after confirming basic wiring integrity. This command individually pulses each injector while the engine is running and measures the resulting drop in fuel rail pressure. It provides a direct comparison of each injector's performance to isolate a weak, clogged, or failing one without having to physically remove it.
• GDS2 / Tech2 (or equivalent professional scanner): Injector Circuit Status (Live Data PID) — Monitor this parameter while performing a 'wiggle test' on the wiring harness. The status should read 'OK'. If it changes to 'Fault' or 'Open' while manipulating the harness, it confirms an intermittent wiring issue.

Wiring & Ground Locations

• G112 — Rear of the engine, mounted to the rear cylinder head (Bank 1).. This is a primary ground point for Bank 1 components. A loose or corroded connection here can cause erratic voltage and trigger circuit low codes for injectors 1, 3, or 5.
• G110 — Right front of the engine, mounted to the cylinder head (Bank 2).. While cylinder 5 is on Bank 1, a poor engine-to-chassis ground network can cause floating voltages and unpredictable issues across all systems. Ensuring all major engine grounds are clean and tight is a crucial step.
• X160 / X161 — Multi-way harness connectors located at the rear of the intake manifold.. These are the main junction connectors between the main engine harness and the injector sub-harnesses. They are a key point for testing continuity to the ECM or to the injector without having to access the full length of the harness.
• ECM Connector X1 — The ECM is located on the front of the engine. X1 is the 73-pin connector, often black with a blue TPA lock.. This is where the control signals for the fuel injectors originate. Probing for voltage and continuity at the specific pin for the cylinder 5 injector is the final step in diagnosing a wiring fault before condemning the ECM.

Real Owner Repair Stories

• YouTube video by 'Speedmotion' (2007 GMC Acadia) — Check engine light with injector circuit codes for cylinders 2, 4, and 6.
  ❌ Tried (didn't work) Initial assumption was that all three injectors or coils had failed simultaneously, which was unlikely.
  ✅ What actually fixed it The technician found that the power supply wire for the entire bank of injectors (Bank 2) was faulty at a splice point (J133), causing all three cylinders on that bank to lose power and set codes. This highlights the importance of checking shared power/ground wires when multiple components on the same circuit fail.
• YouTube video by 'The ASE Mechanic' (GMC Acadia with P0300 (Random/Multiple Misfire)) — Intermittent misfire on cylinders 2, 4, and 6.
  ❌ Tried (didn't work) The owner drove the car for two weeks with the issue, leading to catalytic converter damage.
  ✅ What actually fixed it A loose 8mm ground bolt on the engine block was found to be the cause of the intermittent misfire for the entire cylinder bank. Tightening the ground connection resolved the misfire codes.

OEM Part Supersession History

• 12638530 → 12669384 — Standard part revision by GM.
  Heads up: This part number is for the 3.6L LLT engine (approx. 2009-2011). It is not compatible with the 2012-2014 LFX engine, which uses a different, low-impedance injector. Aftermarket sellers recommend replacing all injectors as a set to avoid imbalances in fuel flow and atomization.

Model Year Variations Within This Range

• 2009-2011: These models use the 3.6L LLT V6 engine. The direct fuel injectors are high-impedance, with a coil resistance of approximately 11.8-12.6 Ohms. The correct OEM part number is 12669384.
• 2012-2014: These models use the updated 3.6L LFX V6 engine. The direct fuel injectors are low-impedance, with a coil resistance of approximately 1.2-1.8 Ohms. Using diagnostic resistance values or injectors from the earlier LLT engine will lead to misdiagnosis and improper repairs.