P0204 on 2009-2014 GMC Acadia: Injector Circuit Malfunction Causes and Fixes

What's Unique About the 2009-2014 Gmc ACADIA

For this generation of GMC Acadia and its platform mates (Buick Enclave, Chevy Traverse, Saturn Outlook) with the 3.6L V6 engine, the primary suspect for a P0204 code 🎬 Watch: A breakdown of common P0204 causes and fixes. is not always the injector itself. General Motors issued a Technical Service Bulletin (TSB #PIP4924D) specifically highlighting that the fuel injector wiring harness is prone to rubbing through (chafing) against engine components. This wiring issue is a very common point of failure and should be the first thing investigated before spending money on parts. A particularly notorious spot is near the underhood fuse box, where a broken plastic mounting bracket can allow the harness to sag and get damaged.

Diagnostic Flowchart

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

Generation note: The 2009-2014 year range covers the first generation of the GMC Acadia. This generation used the 3.6L V6 engine, specifically the LLT version from 2009-2011 and the updated LFX version from 2012-2016. The P0204 fault and its common causes, particularly the wiring harness chafe issue detailed in TSB PIP4924D, are consistent across these engine versions and their Lambda platform mates.

Symptoms You May Notice

• Check Engine Light is on
• Rough, unstable idle
• Engine misfiring or stumbling, especially under load
• Noticeable loss of engine power and poor acceleration
• Reduced fuel economy
• "Service Stabilitrak" or "Traction Control Off" message may appear on the dash. This is a programmed response from GM; when the ECM detects a significant engine fault like a misfire, it disables the traction and stability systems as a precaution.
• Engine may enter "Reduced Engine Power" mode.

Most Likely Causes

1. Chafed or Damaged Fuel Injector Wiring Harness 🔴 High Probability → Shop Engine Wiring Harness As documented in GM TSB #PIP4924D, the wiring harness is routed in a way that it can rub against the intake plenum, valve cover bolts, fuel lines, or the cylinder head, causing wires to short out or break. Forum user experiences frequently pinpoint a broken plastic bracket under the underhood fuse box, which allows the main engine harness to move excessively and chafe.
   How to confirm: Carefully inspect the entire fuel injector wiring harness. Pay close attention to where it contacts metal engine parts and especially inspect the harness section near the underhood fuse box. Perform a "wiggle test" on the harness with the engine running, focusing on the fuse box area, to see if it induces a misfire or causes the engine to stumble.
   Typical fix: Repair the damaged section of wire using solder and heat-shrink tubing. Protect the repaired area with high-quality automotive tape (like Tesa tape) and split-loom tubing. Secure the harness away from sharp edges or replace broken mounting brackets to prevent future chafing. In severe cases, the entire engine harness may need replacement.
   Est. part cost: $5-$50 for repair materials, $150-$400 for a new harness
2. Faulty Cylinder 4 Fuel Injector 🟡 Medium Probability → Shop Fuel Injector The direct injection (DI) injectors on the LLT and LFX engines operate under high pressure and can fail internally over time. They can become clogged, shorted, or develop an open circuit in their internal coil.
   How to confirm: After confirming the wiring is good, test the injector. Measure its resistance with a multimeter (see 'specific_diagnostic_values' for year-specific ranges). The most definitive test is to swap the #4 injector with another cylinder's injector (e.g., #2 or #6). Clear the codes and run the engine. If the fault code moves to that cylinder (e.g., P0202 or P0206), the injector is bad.
   Typical fix: Replace the faulty fuel injector. On the Acadia's 3.6L V6, cylinder 4 is on the front bank (Bank 2, near the radiator), making it accessible without removing the intake manifold. It is often recommended to replace all injectors on the same bank, or all six, if they are high-mileage.
   Est. part cost: $40-$120
3. Poor Connection at Injector or ECM ⚪ Low Probability Engine vibration can cause the terminal pins within the injector's plastic connector to loosen or corrode over time, creating high resistance. This issue is noted in other GM TSBs for similar engine platforms.
   How to confirm: Disconnect and inspect the electrical connector at the fuel injector and the main engine harness connectors at the ECM. Look for any signs of corrosion (white or green powder), moisture, or bent/loose pins. A wiggle test on the connector itself may also trigger the fault.
   Typical fix: Clean the connector terminals with electrical contact cleaner. Apply a small amount of dielectric grease to the seal before reconnecting. If the connector pigtail is damaged or the terminals are loose, it will need to be replaced by splicing in a new one.
   Est. part cost: $10-$40 for a new pigtail connector

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is the least likely cause. The internal driver circuit for the #4 injector can fail inside the ECM. This should only be considered after all wiring, connectors, and the injector itself have been proven to be good.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner. Note any other codes present, such as P0304, P0300, or other injector circuit codes (P0202, P0206).
2. Perform a detailed visual inspection of the fuel injector wiring harness as described in TSB #PIP4924D. Look for any signs of rubbing, melting, or damage. Pay special attention to the harness routing near the underhood fuse box and check for a broken mounting bracket.
3. With the engine idling, carefully wiggle the wiring harness in various spots, particularly near the underhood fuse box and around the cylinder heads, to see if you can make the misfire worse or cause it to happen. A user on the ScannerDanner Forum confirmed pulling up on the harness near the fuse box replicated the fault.
4. If no wiring damage is found, test the injector signal. Disconnect the cylinder 4 injector and plug in a 'noid light'. Crank or start the engine; the light should flash, indicating the ECM is sending a pulse. If it doesn't flash, the problem is in the wiring or ECM.
5. If the noid light flashes, test the injector itself. Turn off the engine, disconnect the injector, and measure its resistance with a multimeter set to Ohms. It should be between 11-14 Ohms (2009-2011 LLT) or 1.2-1.8 Ohms (2012-2014 LFX). Compare the reading to the other injectors on the front bank; it should be very similar. If it's an open circuit (infinite resistance) or very different, the injector has failed.
6. As a final confirmation, swap the cylinder 4 injector with the cylinder 2 injector (the one next to it). Clear the codes and run the engine. If the code changes to P0202, you have confirmed the injector is the faulty part.
7. If all tests above pass, the fault may be an intermittent wiring issue that is hard to see, a poor connection at the injector plug, or in rare cases, a faulty ECM driver.

Parts You'll Likely Need

• Fuel Injector (OEM #12638530 (also 12669384, 12611545, 12632255)) — If the injector's internal coil has failed, it must be replaced to restore proper fuel delivery. Part number 12638530 is for the LLT engine and has been superseded by other numbers.
  Trusted brands: ACDelco, Bosch, Delphi
  OEM price range: $80-$120
  Aftermarket price range: $40-$80
• Fuel Injector Connector Pigtail (OEM #ACDelco PT2618 (13580230)) — If the plastic connector or its terminals are corroded, melted, or damaged from vibration, it will need to be spliced into the harness to ensure a solid connection.
  Trusted brands: ACDelco, Dorman, Standard Motor Products
  OEM price range: $25-$40
  Aftermarket price range: $10-$25
• Split Loom and Automotive Tape — Essential for repairing and protecting the wiring harness after fixing a chafed wire, as per TSB #PIP4924D, to prevent the issue from recurring.

Related Codes That Often Appear With This One

• P0304 — This code means 'Cylinder 4 Misfire Detected.' Since P0204 indicates a fuel delivery circuit problem for cylinder 4, a misfire in that same cylinder is a direct and expected consequence.
• P0300 — This code for 'Random/Multiple Cylinder Misfire' can appear if the electrical fault is intermittent or if the wiring damage affects multiple injector circuits, causing general engine instability.
• P0202, P0206 — If the wiring harness damage affects the power or ground supply shared by the entire front bank of injectors (Bank 2), you may see circuit codes for the other cylinders on that bank as well. This is a strong indicator of a harness issue rather than a single failed injector.

Technical Service Bulletins (TSBs) & Recalls

• PIP4924D: SES Light And Misfire With Injector Codes - This bulletin is the primary guide for this issue, advising technicians to carefully inspect the fuel injector wiring harness for chafing or internal breaks before replacing components. It applies to a wide range of GM vehicles with the 3.6L engine.

Platform-Specific Known Issues

• GM Technical Service Bulletin #PIP4924D explicitly calls out the fuel injector wiring harness for potential rub-through and open circuits on 2009-2014 GMC Acadias and its platform mates.
• A common failure point identified by owners is a broken plastic mounting bracket for the engine harness located near the underhood fuse box. When this bracket fails, the harness can sag and make contact with other components, leading to chafing and circuit faults for Bank 2 injectors (P0202, P0204, P0206).

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (2009-2011 3.6L LLT Engine) — expected: 11 - 14 Ohms. Failure: A reading of 0 ohms (short), infinity/OL (open), or significant deviation from this range.
• Fuel Injector Resistance (2012-2014 3.6L LFX Engine) — expected: 1.2 - 1.8 Ohms. Failure: A reading outside this very narrow range indicates an internal injector fault. Using the wrong spec will lead to misdiagnosis.
• Injector Connector Voltage (Key On, Engine Off) — expected: 11.5V - 12.5V. Failure: Low or no voltage indicates a problem with the power supply wire or fuse for the injectors.
• Injector Pulse Width (at normal idle) — expected: 2 - 4 milliseconds (ms). Failure: A value of 0 ms on cylinder 4 while other cylinders show a pulse indicates the ECM is not commanding the injector or the signal is lost.

Scan Tool Commands That Help

• GDS2 / Tech2 (or equivalent professional scanner): Fuel Injector Balance Test — This is a critical functional test when an injector passes resistance checks but is still suspected of being faulty. The tool commands each injector to fire and measures the corresponding drop in fuel rail pressure. If the pressure drop for cylinder 4 is significantly different from the others, it confirms a flow issue (clogged or leaking), differentiating it from a purely electrical fault.
• GDS2 / Tech2 (or equivalent professional scanner): Cylinder Power Balance — This function allows a technician to disable individual cylinders one by one to gauge their contribution to engine speed. Disabling cylinder 4 should cause little to no change in RPM if it's already not firing, helping to confirm the location of the misfire.

Wiring & Ground Locations

• Cylinder 4 Injector Control (ECM Connector X1, Pin 9 on LLT) — On the 2009-2011 LLT engine with the Bosch ECM, the control wire for the #4 injector is typically a Light Blue/Black wire at Pin 9 of the X1 connector.. This is the specific pin on the ECM that sends the ground pulse to fire the cylinder 4 injector. A continuity test between this pin and the injector connector pin can definitively identify a broken wire.
• Cylinder 4 Injector Control (ECM Connector X2, Pin 52 on LFX) — On the 2012-2014 LFX engine with the Delphi ECM, the control wire for the #4 injector is typically a Light Blue/White wire at Pin 52 of the X2 connector.. This is the specific control pin for the cylinder 4 injector on the later model Acadias. Testing continuity to this pin is essential for diagnosing a wiring fault.
• Injector Power Supply (Bank 2) — A Pink/Black wire provides ignition voltage to all injectors on Bank 2 (cylinders 2, 4, 6). This circuit is powered by a dedicated fuse in the underhood fuse block.. If this power supply wire is damaged or the fuse is blown, all three cylinders on the front bank will lose power, likely triggering P0202, P0204, and P0206 simultaneously. This points to a harness or fuse issue, not a single injector failure.
• Engine Block Grounds (G105/G106) — There are several main engine block ground points bolted to the block and cylinder heads, which then connect to the chassis and battery negative terminal.. While not specific to one injector, a poor engine ground can cause widespread electrical issues, including erratic sensor readings and unpredictable behavior from the ECM's injector drivers. Verifying these grounds are clean and tight is a fundamental step in diagnosing any electrical fault.

Real Owner Repair Stories

• ScannerDanner Forum (2008 GMC Acadia 3.6L) — Engine runs fine for 30-45 minutes, then goes into open loop with a severe misfire. Codes P0300, P0202, P0204, and P0206 all appear at once.
  ❌ Tried (didn't work) Initial diagnosis pointed towards a heat-soaked component, but the fact that all three injectors on one bank failed simultaneously suggested a common point of failure.
  ✅ What actually fixed it The wiring harness that runs over the top of the engine was chafed through where it passed near the underhood fuse box. Pulling up on the harness near the fuse box would cause the fault to occur instantly. Repairing the damaged wires in the harness resolved all codes.

OEM Part Supersession History

• 12611545 → 12632255, then 12638530, then 12669384 — Standard part evolution for improved reliability or manufacturing process changes.
  Heads up: These part numbers are for the high-impedance injectors used in the LLT engine (2009-2011). They are not compatible with the LFX engine (2012-2014), which uses low-impedance injectors.

Model Year Variations Within This Range

• 2009-2011: These models use the 3.6L LLT V6 engine, which has high-impedance fuel injectors (~11-14 Ohms), an aluminum intake manifold, and a Bosch ECM. The correct injector part is 12638530 or its supersessions.
• 2012-2014: These models use the updated 3.6L LFX V6 engine. This engine uses low-impedance injectors (~1.2-1.8 Ohms), a composite intake manifold, integrated exhaust manifolds, and a Delphi ECM. The injectors are not cross-compatible with the earlier LLT engine.