GMC Yukon P0204 (2021-2022): Injector Circuit Malfunction Causes and Fixes

What's Unique About the 2021-2022 Gmc YUKON

For this generation of GMC Yukon and its sister platforms (like the Sierra and Tahoe), wiring harness issues are a well-documented weak point. Multiple Technical Service Bulletins (TSBs) point to problems with chafing, poor terminal tension, and broken pins in connectors. For the 3.0L Duramax diesel, TSB #21-NA-149 identifies specific chafe points on top of the generator and at a PCV hose clamp. Technicians also report a high incidence of 'fretting corrosion'—vibration causing a poor connection and visible black dust inside the injector pigtail 🎬 Watch: How terminal fretting causes these specific misfire codes.—especially on cylinder 4. While the code points to the injector, the root cause is frequently the wiring leading to it, making a thorough harness inspection the critical first step.

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 (may be flashing)
• Rough or unstable idle
• Engine misfire (may also set a P0304 code)
• Hesitation or stumbling during acceleration
• Reduced engine power and poor fuel economy
• Vehicle may enter a speed-limited "limp mode"
• "Service Emission System" or "Service ESC" message on the dash.

Most Likely Causes

1. Damaged Engine Wiring Harness or Connector 🔴 High Probability Multiple TSBs (#21-NA-149, #23-NA-027) document issues with the engine harness. On the 3.0L Duramax, the harness for cylinder 4 is known to rub against the steering shaft, valve cover, or get damaged by heat from the EGR pipe. TSB #21-NA-149 specifically calls out inspecting for chafing on top of the generator and at connector X160 for poor pin tension. On V8 models, a known chafe point is where the harness can get pinched by the transmission bell housing. Vibration can also cause 'fretting corrosion' inside the connector itself, visible as black or brown dust, leading to high resistance.
   How to confirm: Visually inspect the entire length of the wiring harness to the cylinder 4 injector. Check specific chafe points: top of the generator (LM2), PCV hose clamps (LM2), and the rear of the engine near the bell housing (V8s). Disconnect the injector and look for black dust inside the connector. Perform a "wiggle test" on the connector and wiring with the engine running to see if it induces a misfire.
   Typical fix: Repair the damaged section of wire and protect the harness from future damage using abrasion-resistant tape or loom. If the connector is the issue, replace the connector pigtail. 🎬 See a quick roadside repair of the cylinder 4 connector. In some cases, the entire injector harness may need to be replaced.
   Est. part cost: $20-$250
2. Faulty Fuel Injector 🟡 Medium Probability While less common than wiring issues, the injector can fail. TSB #22-NA-087 notes that a broken terminal pin inside the harness connector may require replacement of both the injector and the harness, as the pin is part of the injector itself. This makes it difficult to distinguish a harness fault from an injector fault without disassembly.
   How to confirm: After confirming the wiring is good, swap the cylinder 4 injector with an injector from another cylinder (e.g., cylinder 2). Clear the codes and drive the vehicle. If the code changes to P0202, the injector is faulty. If P0204 returns, the problem is in the wiring or PCM. An injector resistance test with a multimeter can also be performed; a healthy LM2 injector should have very low resistance (under 1 ohm), while a gas V8 injector is around 12-14 ohms.
   Typical fix: Replace the faulty fuel injector. For the 3.0L Duramax, this also requires replacing the injector fuel pipe and programming the new injector's flow rate into the ECM. Per TSB #22-NA-087, it is recommended to replace the injector harness at the same time.
   Est. part cost: $150-$400

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): This is a rare cause. The PCM's internal driver for the injector circuit can fail, but all other possibilities, especially wiring, should be exhaustively ruled out first. GM specifically warns against replacing the ECM for this code without a thorough harness inspection in TSB #21-NA-149.

Diagnosis Steps

1. Scan for all diagnostic trouble codes. Note if any other injector codes (P020x) or misfire codes (P030x) are present.
2. Perform a thorough visual inspection of the engine wiring harness, focusing on the path to the cylinder 4 injector. On the 3.0L LM2, check on top of the generator and near the PCV system. On V8s, check the back of the engine near the transmission bell housing.
3. Disconnect the electrical connector at the cylinder 4 injector. Inspect for loose or corroded pins and look for a fine black or brown dust, which indicates fretting corrosion from vibration.
4. With the engine running, carefully wiggle the wiring harness and connector for cylinder 4. If this causes a change in how the engine runs, a wiring fault is likely.
5. Disconnect the injector and use a multimeter to check the injector's internal resistance. Compare the reading to the manufacturer's specification (e.g., <1 ohm for LM2 diesel, ~13.5 ohms for L84 gas). A reading far outside the spec indicates a failed injector.
6. Use a 'noid light' to test the injector connector. The light should flash steadily when the engine is cranked or running, indicating the PCM is sending a pulse signal. If the light is off, very dim, or stays on continuously, there is a problem in the wiring or the PCM.
7. If wiring and signal are confirmed good, consider swapping the injector to another cylinder to confirm if the injector itself is the fault.
8. If all wiring and the injector are confirmed to be good, the final possibility is a fault in the PCM, but this is rare.

Parts You'll Likely Need

• Fuel Injector Wiring Harness (3.0L Duramax LM2) (OEM #40009605 (supersedes 55513485, 55508024, 55510039, 55512145)) — This is the most common failure point. The entire harness is often replaced due to chafing or internal breaks, as recommended by TSBs. A Reddit user confirmed replacing this part (P/N 40009605) fixed their P0204 code.
  Trusted brands: ACDelco (OEM)
  OEM price range: $80-$150
• Fuel Injector Connector Pigtail (OEM #ACDelco 19368140 (for L5P, may cross-reference)) — If the damage is isolated to the connector due to heat or vibration (fretting), replacing just the pigtail is a cost-effective repair instead of the entire harness.
  Trusted brands: ACDelco, Dorman, Fleece Performance
  OEM price range: $40-$60
  Aftermarket price range: $20-$50
• Fuel Injector (3.0L Duramax LM2) (OEM #55506244) — If the injector itself has failed electrically, or if the terminal pin inside the harness is broken, both may need to be replaced as per TSB #22-NA-087.
  Trusted brands: ACDelco (OEM), Bosch
  OEM price range: $250-$400
  Aftermarket price range: $150-$300

Related Codes That Often Appear With This One

• P0304 — P0304 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.
• P0201, P0202, P0203, P0205, P0206 — TSB #22-NA-087 and other related bulletins list all injector codes together, suggesting a common failure point in the harness (like connector X160) or a systemic issue with connector design can affect multiple injector circuits.
• P0216 — This code for 'Fuel Injection Timing Control Circuit' is often seen with P020x codes on the 3.0L Duramax, as noted in TSB #22-NA-087 and owner reports, indicating a broader fuel system electrical issue often stemming from the harness.

Technical Service Bulletins (TSBs) & Recalls

• 22-NA-087: Malfunction Indicator Lamp (MIL) Illuminated with DTC P0201, P0202, P0203, P0204, P0205, P0206 and/or P0216 Set.
• 21-NA-149: Engine Wire Harness Chafing / IPC Gauges Sweep / IPC Warning Message / SES/Check Engine/MIL / No Start / No Crank / Runs Rough / Stalls / Reduced Engine Power / Various DTCs.
• 23-NA-027: Poor Engine Performance, Engine Misfires, Malfunction Indicator Lamp (MIL) Illuminated.

Platform-Specific Known Issues

• TSB #22-NA-087: Specifically calls out P020x codes on 2021-2022 models with the 3.0L Diesel engine. It states the cause may be a broken terminal pin inside the injector harness connector and recommends replacing BOTH the fuel injector (55506244) and the injector wiring harness (55513485, now superseded) to ensure a complete repair.
• TSB #21-NA-149: This is a widespread bulletin for engine wiring harness chafing on 2019-2023 GM trucks and SUVs. For the 3.0L LM2 engine, it identifies specific inspection points for P020x codes: poor terminal tension at connector X160, chafing on top of the generator, and chafing on a PCV hose clamp.
• TSB #23-NA-027: This bulletin

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (3.0L LM2 Diesel) — expected: 160k - 190k Ohms (160,000-190,000 Ω). Failure: A reading significantly outside this range indicates a faulty piezo injector.
• Fuel Injector Resistance (5.3L L84 / 6.2L L87 Gas) — expected: 11 - 14 Ohms. Failure: An open circuit (infinite resistance) or a reading far outside this range indicates a faulty injector.
• Injector Circuit Voltage (Key On, Engine Off) — expected: ~12 Volts (Battery Voltage). Failure: Low or no voltage on the power supply wire points to a problem in the supply circuit (fuse, relay, or open wire).
• Low-Pressure Fuel System (3.0L LM2 Diesel) — expected: 74 - 87 PSI. Failure: Pressure outside this range from the in-tank lift pump can indicate a failing pump, causing starvation of the high-pressure pump.

Scan Tool Commands That Help

• GDS2 (GM Factory Tool): Injector Flow Rate Programming — Required after replacing a fuel injector on the 3.0L LM2 diesel engine to input the new injector's specific flow rate (trim code) into the ECM for proper fuel delivery calibration. Found under: ECM > Control Functions > Injector Flow Rate Programming.
• GDS2 (GM Factory Tool): Cylinder Balance Test — Used as a diagnostic step to identify which cylinder is contributing least to engine power, helping to confirm the location of the misfire before disassembling parts.
• Aftermarket Scan Tool (e.g., Snap-on, Autel): Injector Rate Programming / IQA — Same function as the GDS2 command. However, a critical step on many aftermarket tools is to prepend 'F7' to the trim code found on the injector (e.g., enter 'F7ABCDEFGH'). The programming will fail without this prefix.

Wiring & Ground Locations

• Cylinder #4 Injector Connector (3.0L LM2) — Located on the driver's side of the engine, second cylinder from the front, underneath the hot EGR crossover pipe.. This specific location subjects the connector to extreme heat cycles, which can degrade the plastic and lead to poor terminal tension. Combined with engine vibration, this is the primary cause of fretting corrosion and intermittent open circuits for P0204.
• G103 — Left rear of the engine compartment, on the cowl, above the power brake booster.. This is a major ground point for the Body Control Module (BCM), Instrument Panel Cluster (IPC), and the Data Link Connector (DLC). A poor connection here can cause a wide range of electrical issues and communication errors between modules, including the ECM.
• G102 — On the rear of the left (driver's side) cylinder head.. Provides the ground path for the ignition coils on V8 models. While not directly tied to the injector circuit, a faulty ground here can introduce electrical noise into the engine management system, potentially causing misdiagnosis.

Real Owner Repair Stories

• YouTube channel 'DadsGarage Diagnostic Specialist' (2019 Silverado with L5P Duramax (engine platform with the same known injector connector issue)) — Reduced Engine Power message, Check Engine Light on, codes P0204, P0300, and P0304.
  ❌ Tried (didn't work) The technician, based on experience, went directly to inspect the cylinder 4 injector connector rather than trying other diagnostics first.
  ✅ What actually fixed it The cylinder 4 injector connector was found to have visible black/brown dust (fretting corrosion) and one of the female pins had extremely loose tension. Replacing the connector pigtail resolved the issue. The video clearly shows the dust and the loose pin falling out, confirming this is a mechanical connection failure, not a wiring break.

When the Usual Fixes Don't Work

• While Pass 2 correctly identifies wiring as the most likely cause, extensive technician reports and repair videos indicate that the diagnostic process for P0204 on this platform should not just start with a general harness inspection, but should go directly to the cylinder 4 injector connector itself. The prevalence of fretting corrosion and loose pins at this specific connector is so high that it should be considered the primary suspect, ahead of harness chafing elsewhere. A common misdiagnosis is performing a static resistance test on the circuit, finding it 'good,' and then replacing the injector, only for the intermittent fault to return.

OEM Part Supersession History

• 55508024, 55510039, 55512145, 55513485, 40009103 → 40009605 — This is the injector wiring harness for the 3.0L LM2 diesel. The part has been superseded multiple times, likely due to revisions to improve durability and prevent the known chafing and connector fretting issues.
• LM2 Fuel Injector (55506244) → N/A
  Heads up: The fuel injectors for the 3.0L LM2 diesel (used in 2021-2022 Yukons) are NOT interchangeable with the injectors used in the later 3.0L LZ0 diesel (used in 2023+ trucks). The LZ0 uses a different injector design to accommodate its updated engine components.

Model Year Variations Within This Range

• 2021-2022: The 3.0L Duramax engine used in the Yukon for this period is the LM2 version. The updated LZ0 engine with different injectors and internal components was introduced in 2023 on the Silverado/Sierra trucks, but not the SUVs. Therefore, parts like injectors are specific to the LM2 for these Yukons.