Stop Paying the Dealer for Your 2015 Silverado 5.3L P0306 & P0206

Overview

This combination of codes, P0306 (Cylinder 6 Misfire) and P0206 (Cylinder 6 Injector Circuit Malfunction), points directly to an electrical or electronic failure at the fuel injector for cylinder 6 on your 2015 Silverado 5.3L. This is not a typical spark or compression issue. The ECM has detected a break or short in the injector’s electrical circuit, preventing it from firing fuel into that cylinder.

The most common root cause for this specific pairing on the 2015 5.3L (L83 EcoTec3) is a failed fuel injector. These engines use a high-pressure direct injection system, and the injectors are known for developing internal electrical shorts. The repair usually involves replacing the injector. The GM part number for the injector is 12662027 (new) or 12662026 (remanufactured). Expect to pay between $80 and $120 for a single new injector at a dealership or quality parts supplier.

Labor time for a single injector replacement on this engine is approximately 2.5 to 3.0 hours. This includes removing the intake manifold, fuel rail, and high-pressure fuel line. Total cost for this repair at a shop typically falls between $350 and $500, including parts and labor. If you have high mileage (over 100,000 miles), it is often wise to replace all eight injectors at once to prevent future failures, though the cost rises to around $1,200 to $1,800.

Before replacing the injector, a technician must verify the wiring harness for cylinder 6. The injector connector (terminal position 6 on the fuel injector harness) can become corroded or damaged. Check for broken wires near the connector or at the engine harness junction behind the intake. If the wiring is intact, the injector itself is almost certainly faulty. A simple resistance test at the injector pins should show about 12-15 ohms; an open circuit or short confirms the failure.

Do not ignore P0306 and P0206 together. Driving with a dead injector will dump raw fuel into the cylinder, washing oil off the cylinder walls and potentially damaging the piston rings or catalytic converter. If the misfire is severe, you may also notice a strong fuel smell from the exhaust and a rough idle. Addressing the injector or wiring issue promptly is the only safe path for your 2015 Silverado 5.3L.

Symptoms

What Silverado Owners Experience with 2015 5.3L Cylinder 6 Misfire (P0206 & P0306)

When a 2015 Silverado with the 5.3L EcoTec3 (L83) engine triggers both a P0306 (Cylinder 6 Misfire) and a P0206 (Injector Circuit Malfunction – Cylinder 6), the problem is almost always electrical or injector-related, not a mechanical failure. Here is exactly what owners report:

• Rough Idle and Shaking at Stoplights: The truck will idle with a pronounced shudder, especially when warm. The vibration is often felt in the steering wheel and seat, and the check engine light flashes to indicate a catalyst-damaging misfire.
• Loss of Power Under Load: When accelerating from a stop or climbing a grade, the engine feels flat and hesitant. You may notice a lack of response when pressing the gas pedal, and the transmission may hunt for gears as power delivery is uneven.
• Fuel Smell and Poor Fuel Economy: Because the fuel injector on cylinder 6 is not firing correctly (P0206), raw fuel is dumped into the cylinder and exhaust. Owners report a strong gasoline smell from the tailpipe and a noticeable drop in MPG, often 3-5 miles per gallon less than normal.
• Hard Start or Extended Cranking: Some owners experience a longer crank time when the engine is hot. This is due to fuel pressure bleeding off or the injector leaking internally when the circuit is compromised.
• Clicking or Ticking Noise from Engine Bay: A failed injector or a shorted injector driver in the engine control module (ECM) can cause a rapid, metallic clicking sound from the top of the engine, specifically near cylinder 6 on the driver’s side.

Common Root Cause: The P0206 circuit code strongly points to an electrical fault. On this engine, the injector harness chafes against the intake manifold or the valve cover, shorting the injector circuit. Replacing the injector alone often fails to fix the problem if the harness is damaged. The recommended repair includes replacing the cylinder 6 fuel injector (GM Part #12668393, approximately $85 each) and carefully inspecting and repairing the injector harness. Labor is typically 1.5 to 2.0 hours for diagnosis and repair. If the harness is severely corroded, a new engine harness section or a full engine harness replacement (GM Part #23489107, approximately $250-$350) may be necessary.

Diagnosis

Diagnostic Process: 2015 Silverado 5.3L Cylinder 6 Misfire (P0206 & P0306)

When you have both a P0306 (Cylinder 6 Misfire) and a P0206 (Cylinder 6 Injector Circuit) on a 2015 Silverado with the 5.3L (L83) engine, the injector circuit fault is almost always the root cause. Do not throw parts at it. Follow this step-by-step diagnostic process.

1. Verify the Codes and Freeze Frame Data
   Confirm both DTCs are current, not history. Record freeze frame data to see engine load and RPM at the time of the misfire. A P0206 indicates a problem in the injector control circuit, not just a mechanical misfire.
2. Visual Inspection of Cylinder 6 Wiring
   Focus on the harness near the back of the intake manifold on the driver’s side. Cylinder 6 injector is the second from the rear. Look for chafed, pinched, or melted wires, especially where the harness contacts the EGR tube or the hot exhaust manifold. GM TSB 16-NA-151 addresses harness chafing on these engines.
3. Test Injector Electrical Resistance
   Disconnect the injector connector for Cylinder 6. Using a digital multimeter, measure resistance across the two injector pins. Specification is 11-14 ohms at 68°F. An open circuit (OL) or a short (below 5 ohms) means a failed injector. GM part number for the injector is 12668393 (approx. $85-$110 each).
4. Check for Short to Ground or Power
   With the injector disconnected and the ignition ON (engine OFF), check for voltage at the harness connector. You should see battery voltage (12.6V) on one pin (the fused supply from the ECM). The other pin is the control circuit. If you see voltage on both pins, or zero volts on the supply pin, there is a wiring fault.
5. Perform a Noid Light Test
   This is the best quick test for a P0206. Connect a noid light to the Cylinder 6 injector harness. Crank the engine. The light should flash brightly and steadily. If it does not flash, the ECM driver for Cylinder 6 is likely damaged, or the wiring between the ECM and the injector is open. Do not use a test light to back-probe the ECM connector; use a noid light only.
6. Swap Injectors (If Electrical Test Passes)
   If resistance is good and the noid light flashes, swap the Cylinder 6 injector with Cylinder 1 injector. Clear codes and run the engine. If the misfire moves to Cylinder 1 (P0301 appears), the injector is faulty. If the P0206 stays on Cylinder 6, the problem is in the wiring or ECM.
7. Check ECM Connector and Wiring Continuity
   If the noid light test fails, disconnect the ECM (located under the hood, driver side near the battery). Check continuity between the Cylinder 6 injector control wire (pin X2-32 on the ECM connector) and the injector harness. Resistance should be less than 1 ohm. If open, repair the wire. If shorted to ground, inspect for a pinched wire.
8. Consider ECM Failure (Rare but Possible)
   If all wiring and injector tests pass, and the noid light does not flash, the ECM driver for Cylinder 6 may have failed. This is uncommon on the 2015 Silverado but can happen after a short circuit. ECM replacement requires programming and is typically a $800-$1,200 job at a dealer (labor 1.5-2.5 hours plus part).
9. Clear Codes and Road Test
   After repair, clear all DTCs with a scan tool. Drive the truck under the same conditions as the freeze frame data (usually light to moderate acceleration). Monitor misfire counts for Cylinder 6. Zero counts after a 10-minute drive confirms a successful repair.

Labor Estimate: Expect 1.0-1.5 hours for diagnosis if you follow this process. Injector replacement on the 5.3L is 2.5 hours labor (requires intake manifold removal). Wiring repair is typically 1.0-2.0 hours depending on location.

Fix

Step-By-Step Fix: 2015 Silverado 5.3L – Cylinder 6 Misfire (P0206 & P0306)

These two codes together—P0306 (Cylinder 6 Misfire) and P0206 (Cylinder 6 Injector Circuit)—point to a specific electrical or injector problem on that cylinder, not a general fuel or spark issue. Here is the diagnostic and repair sequence I use.

1. Safety First & Initial Inspection
   Disconnect the negative battery cable. Remove the engine cover (two 10mm bolts). Inspect the wiring harness near the rear of the intake manifold on the driver’s side. Look for chafed, melted, or rodent-damaged wires, especially where the harness contacts the EGR tube or valve cover. This is the most common cause for both codes on this generation.
2. Swap the Injector
   Swap the Cylinder 6 fuel injector with Cylinder 8 (same bank, easy access). Clear codes with a scanner. If the code moves to P0208/P0308, the injector is internally shorted. Replace it with a GM Genuine Part 12668393 (approx. $85–$110). Labor: 0.5 hours if you are experienced with the fuel rail crossover line.
3. Test the Injector Harness Connector
   If the code stays on Cylinder 6 after swapping injectors, the problem is in the harness or ECM. Unplug the injector connector at Cylinder 6. Using a multimeter set to ohms, check resistance between the two injector terminals on the harness side. You should see 11–14 ohms. An open circuit (OL) or short (0 ohms) means a broken wire or a short to ground.
4. Check for 12V Power and Ground at the Connector
   With the key ON (engine OFF), probe the harness connector at Cylinder 6. One pin should show battery voltage (12.5V+). The other pin is the ECM control ground. If you have no power, check the 10-amp injector fuse in the underhood fuse block (Fuse #38, labeled INJ 1). If the fuse is blown, you have a shorted injector or a pinched wire.
5. Inspect the Engine Harness at the Back of the Driver’s Head
   Remove the intake air duct. Unclip the main engine harness from the rear of the cylinder head. Look for the common failure point: where the injector sub-harness for cylinders 6 and 8 rubs against the sharp edge of the valve cover or the cylinder head casting. Repair any bare wires with heat-shrink butt connectors. This repair typically costs $0 in parts but takes 1.5–2.0 hours of labor.
6. Test the ECM Driver (Last Resort)
   If all wiring checks good and the fuse is fine, the ECM driver for Cylinder 6 may be fried. Perform a “noid light” test at the Cylinder 6 injector connector while cranking. If the noid light does not flash, but the wiring is intact, the ECM is likely bad. A remanufactured GM ECM 12665267 will run about $250–$350, plus programming (about $150 at a dealer or qualified shop).

Pro Tip: On this 2015 model, I see the harness chafe at the rear of the driver’s head more often than a bad injector or ECM. Always inspect the wiring before buying a new injector. Expect 1.5–2.0 hours total labor for a full diagnosis and harness repair.