P0261 on 2010-2014 Cadillac CTS: Cylinder 1 Injector Circuit Low Causes and Fixes

What's Unique About the 2010-2014 Cadillac CTS

On this generation of Cadillac CTS with the 3.0L or 3.6L V6 engines, wiring issues are a known possibility. A General Motors Technical Service Bulletin (TSB) mentions a wide range of injector circuit codes, including P0261, that can be caused by problems in the engine wiring harness. This suggests that before replacing the injector itself, a thorough inspection of the wiring for chafing or damage is critical, as it's a documented weak point. The engine's movement can cause the harness to rub against brackets or other components, leading to shorts.

Diagnostic Flowchart

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Symptoms You May Notice

• Check Engine Light is on
• Rough or shaking idle
• Engine misfire, which may feel like a stumble or hesitation
• Reduced engine power and poor acceleration
• Decreased fuel economy
• In some cases, difficulty starting the engine

Most Likely Causes

1. Damaged Fuel Injector Wiring or Connector 🔴 High Probability → Shop Fuel Injector As noted in TSB #PIP4924D, the engine wiring harness can be a source of various injector circuit faults. Wires can chafe against engine components like brackets, the cylinder head, or the dipstick tube, causing a short to ground and a low voltage condition. The injector connector itself can also become loose, corroded, or damaged.
   How to confirm: Visually inspect the wiring harness leading to the cylinder 1 fuel injector. Check for any signs of rubbing, melting, or corrosion. Unplug the connector and inspect the pins for damage, corrosion, or being loose. Use a multimeter to check for continuity and for a short to ground on the control wire between the ECM and the injector connector. A "wiggle test" on the harness while the engine is running can sometimes reveal an intermittent short.
   Typical fix: Repair the damaged section of the wire or replace the connector pigtail. In severe cases, the entire engine wiring harness may need replacement. Use of dielectric grease on the connector pins can help prevent future corrosion.
   Est. part cost: $10-$50 for a connector pigtail
2. Faulty Cylinder 1 Fuel Injector 🔴 High Probability → Shop Fuel Injector
   How to confirm: The most definitive test is to swap the cylinder 1 fuel injector with an injector from another cylinder (e.g., cylinder 3). Clear the codes and drive the vehicle. If the code changes to P0267 (Cylinder 3 Injector Circuit Low), the injector is faulty. You can also measure the injector's internal resistance with a multimeter. For these high-impedance injectors, a typical reading should be between 11-17 ohms. A reading of 'OL' (open) or significantly lower than the others indicates a failed injector.
   Typical fix: Replace the faulty fuel injector. It is often recommended to replace the upper intake manifold gaskets at the same time. Some owners choose to replace all 6 injectors as a preventative measure 🎬 See this walkthrough for replacing a fuel injector on the 3.6L engine, especially on higher mileage vehicles.
   Est. part cost: $70-$200
3. Faulty Powertrain Control Module (PCM/ECM) ⚪ Low Probability → Shop Engine Control Module (ECM)
   How to confirm: This should be the last step after exhaustively ruling out all wiring and component failures. A specialized scan tool can be used to check the injector driver circuit within the PCM. This is a rare failure and misdiagnosis is common.
   Typical fix: Replace and reprogram the Powertrain Control Module.
   Est. part cost: $400-$1000

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner and note any other codes present.
2. Visually inspect the wiring harness for the cylinder 1 fuel injector. On the V6 engines, cylinder 1 is the front-most cylinder on the passenger's side (right bank). Look for chafing, melting, or loose connections, paying close attention to where the harness might rub against engine brackets or the cylinder head.
3. Inspect the injector connector itself for corrosion or bent pins. Ensure it is securely latched.
4. Use a multimeter to check for battery voltage on one pin of the injector connector with the key on. The other pin is the control wire that gets pulsed to ground by the ECM.
5. Use a noid light on the cylinder 1 connector. Start the engine; the light should flash steadily, indicating the ECM is sending a signal. If it's dim, off, or stays on constantly, the problem is likely in the wiring or ECM.
6. If the wiring and signal appear correct, test the injector. Turn the engine off, disconnect the injector, and measure its resistance with a multimeter set to ohms (Ω). A healthy injector for this engine should read in the 11-17 ohm range. Compare it to another injector on the same engine; they should be within 0.5 ohms of each other.
7. If tools are limited, swap the cylinder 1 injector with another one (e.g., cylinder 3). Clear the codes, run the engine, and see if the fault code moves to the new cylinder (P0267). If it does, the injector is bad. If P0261 returns, the problem is in the wiring or ECM.

Parts You'll Likely Need

• Fuel Injector (OEM #12638530 (may be superseded by 12669384)) — The internal coil of the injector can fail, creating a short or open circuit, which triggers the low voltage code.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $120-$180
  Aftermarket price range: $70-$130
• Fuel Injector Connector Pigtail (OEM #ACDelco PT2160 / GM 13576411) — If the original connector is corroded, melted, or the locking tab is broken, a new pigtail must be spliced into the harness to ensure a solid electrical connection.
  Trusted brands: ACDelco, Dorman, Wells
  OEM price range: $25-$45
  Aftermarket price range: $10-$25
• Upper Intake Manifold Gasket Set (OEM #ACDelco 12627110) — The intake manifold must be removed to access the fuel injectors on the V6 engines. These gaskets are single-use and must be replaced to prevent vacuum leaks.
  Trusted brands: ACDelco, Fel-Pro, Mahle
  OEM price range: $40-$60
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• P0301 — This code means 'Cylinder 1 Misfire Detected'. Since P0261 indicates a problem with fuel delivery to cylinder 1, a misfire in that same cylinder is a direct consequence.
• P0201 — This is a more generic 'Injector Circuit/Open - Cylinder 1' code. It often appears with P0261 as they both point to an electrical fault in the same circuit.
• P2149 — This code for 'Fuel Injector Group B Supply Voltage Circuit/Open' can appear alongside P0261. The ECM groups injectors, and a fault in one can sometimes trigger a group-level code.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: Service Engine Soon Malfunction Indicator Lamp on and a misfire. This bulletin lists P0261 among many other injector codes that could be set due to a wiring issue. [⭐ MANUFACTURER TSB — highest authority]

Platform-Specific Known Issues

• TSB #PIP4924D points to potential chafing or damage in the engine wiring harness as a cause for a group of injector-related DTCs, including P0261. This makes a thorough wiring inspection particularly important on these vehicles. [⭐ MANUFACTURER TSB — highest authority]
• Owners and technicians have noted that due to engine movement, the harness can rub against various points, including the ECM bracket, cylinder heads, and other sharp edges in the engine bay, leading to a short-to-ground condition that causes the P0261 code.

Mechanic-Grade Diagnostic Values

• Fuel Injector Coil Resistance (All GDI Engines) — expected: 1.2 to 1.8 Ohms at room temperature.. Failure: A reading near zero (shorted), infinite/OL (open), or significantly outside the specified range indicates a failed injector.
• Ground Circuit Resistance — expected: Less than 0.1 Ω. Failure: A value higher than 0.1 Ω indicates a poor ground connection that requires cleaning or repair.
• High-Pressure Fuel Rail Pressure at Idle — expected: 1.9-5.0 MPa (276-725 PSI). Failure: Pressure that is significantly below, above, or fluctuating erratically can indicate a problem with the high-pressure fuel system.

Scan Tool Commands That Help

• GDS2 / Tech2: Fuel Injector Balance Test — This bidirectional command is used after confirming the electrical circuit is intact. The tool pulses each injector for a precise duration and measures the corresponding drop in fuel rail pressure. An injector that causes a significantly different pressure drop compared to others is likely clogged or mechanically faulty.
• GDS2 / Tech2: Cylinder Power Balance / Injector Kill — This active test allows the technician to disable one injector at a time while the engine is running. A good cylinder will show a noticeable drop in RPM when its injector is disabled. If disabling the cylinder 1 injector causes little or no change in RPM, it confirms that cylinder was not contributing power, pointing to a fault in that injector's circuit or the injector itself.

Wiring & Ground Locations

• G101 — Located at the left front of the engine, on the lower block.. This is a primary ground for the Engine Control Module (ECM). A poor connection at G101 can cause erratic behavior and low voltage faults in the injector driver circuits controlled by the ECM.
• Injector Harness Chafe Points — Commonly found where the harness rubs against the intake plenum, valve cover bolts, high-pressure fuel line, and the side of the cylinder head.. TSB #PIP4924D specifically identifies harness chafing as a primary cause for injector circuit codes like P0261. The insulation wears away, causing the control wire to short to ground, which the ECM detects as a 'Circuit Low' condition.

OEM Part Supersession History

• 12638530, 12632255, 12611545 → 12669384 — Standard part revision and consolidation by the manufacturer.
  Heads up: This part is ONLY for the 2010-2011 3.0L LF1 and 3.6L LLT engines. It is NOT compatible with the 2012-2014 3.6L LFX engine.

Model Year Variations Within This Range

• 2010-2011: These models use the 3.0L LF1 or 3.6L LLT V6 engine. They feature an aluminum intake manifold, a Bosch ECM, and use fuel injector part number 12638530 (or its successor 12669384).
• 2012-2014: These models use the updated 3.6L LFX V6 engine. This engine has integrated exhaust manifolds, a composite intake manifold, a Delphi ECM, and uses different, incompatible fuel injectors (e.g., part number 12634126). Using an LLT injector in an LFX will result in fitment and fueling issues.