2015 Silverado 2015 Silverado 5.3L Cylinder 6 Misfire P0206 and P03…

A P0206/P0306 combo on your 2015 Silverado 5.3L means the Engine Control Module is detecting a misfire on cylinder 6 because it’s not getting a proper signal to the fuel injector, likely due to a faulty injector, wiring issue, or connector problem.

Cost & Time: At a shop, expect to pay $450-$750 (1.5-2.5 hrs labor @ ~$150/hr + part). A DIY fix with a new injector (GM part #12674590, ~$120) could take 2-3 hours if you’re experienced.

Action: Before replacing the injector, always swap the suspect injector with one from another cylinder to see if the misfire code follows it.

For specific year variations and engine codes, see the detailed sections below.

What Code Means

Vehicle: 2015 Chevrolet Silverado with 5.3L EcoTec3 (L83) V8 engine.

Diagnostic Trouble Codes (DTCs):

• P0206: Injector Circuit – Cylinder 6
• P0306: Cylinder 6 Misfire Detected

What This Means:

These codes are directly related. P0206 indicates an electrical fault in the fuel injector circuit specifically for cylinder 6. This fault is causing that injector to not operate correctly, which leads to the cylinder misfire recorded as P0306. Your first diagnostic steps should focus on the injector circuit for cylinder 6.

First Things to Check (In This Order):

1. Visual Inspection & Connector Check:
   
   Locate the fuel injector for cylinder 6 (front bank, driver’s side, third injector back from the front). Check the injector’s electrical connector for damage, corrosion, or being loose. Unplug it, inspect the terminals, and plug it back in firmly. Check the wiring harness back about 6-8 inches for any chafing or burns.
2. Swap Test (Most Effective First Test):
   
   Swap the fuel injector from cylinder 6 with the injector from cylinder 8 (or another cylinder on the same bank). Clear the codes and run the engine. If the misfire code moves to the other cylinder (e.g., P0308), the injector itself is faulty. If the code stays at P0306/P0206, the problem is in the wiring or control circuit.
3. Electrical Tests:
   
   If the code stayed, perform circuit checks with a digital multimeter.
   
   – Check injector coil resistance: It should be between 10-14 ohms at room temperature.
   
   – Check for a short to ground or voltage on the control circuit with the connector disconnected.
   
   – Use a noid light or scan tool bidirectional control to check for the injector pulse signal.

Common Causes & Parts:

• Faulty Fuel Injector: GM Part # 12674590 (Service Kit). Cost: ~$120 – $150 each.
• Faulty Wiring/Connector: Repair harness or replace connector.
• Less Likely but Possible: Issue with the Engine Control Module (ECM) driver for that circuit.

Labor Note: Diagnosing and replacing a single fuel injector on this engine typically pays 1.2 to 1.5 hours of labor. If the intake manifold must be removed for access, that time is included.

Always start with the simple swap test. It will save you significant diagnostic time and confirm whether you need a ~$150 part or need to trace a wiring fault.

Causes

Root Causes of 2015 Silverado 5.3L Cylinder 6 Misfire (P0206/P0306)

Diagnosing this specific misfire requires a systematic approach. The P0206 (Injector Circuit) code often points directly to the issue, but mechanical causes can also trigger it. Here are the root causes ranked from most to least frequent for this model year.

1. Faulty Fuel Injector (Most Common)
The Gen IV 5.3L (L83) is notorious for injector failures, especially on cylinders 6 and 7. Carbon buildup or internal electrical faults cause high resistance or an open circuit.

Part: GM Injector Assembly (12661441) – ~$220 each.

Labor: 2.0-2.5 hours for bank access and replacement.

2. Injector Circuit Issue (Wiring/Connector)
The wiring harness near the cylinder 6 injector can suffer from chafing, heat damage, or a loose/corroded connector. This is a very common companion to, or cause of, the P0206.

Part: Injector connector/pigtail (13577375) if needed – ~$25.

Labor: 1.0-1.5 hours for diagnosis and repair.

3. Faulty Ignition Coil
While P0206 points to fuel, a weak coil can cause a P0306 alone. However, a severe coil failure can sometimes confuse the PCM. Always swap coil #6 with another cylinder to test.

Part: GM Coil (12677859) – ~$75.

Labor: 0.3 hours for a simple swap test.

4. Carbon-Fouled Spark Plug
Direct injection leads to carbon buildup on intake valves. This can cause poor air/fuel mixing, leading to a misfire that may set both codes. Cylinder 6 is a common victim.

Part: GM Spark Plug (12621244) – ~$15 each.

Labor: 0.5 hours for plug R&R, plus diagnostics.

5. Low Compression or Internal Engine Fault (Least Common)
A worn valve, broken valve spring, or damaged piston/ring in cylinder #6 will cause a persistent mechanical misfire. This is the final diagnostic step if all electrical and fuel components check out.

Labor: 1.0 hour for compression/leak-down testing.

Note: Repair costs here vary widely, from a valve spring (~$500+) to major engine work.

Diagnostic Priority: Start by checking/cleaning the injector connector and swapping the fuel injector and coil with adjacent cylinders to see if the misfire follows the component. This is the fastest way to isolate the most common faults.

Diagnosis

Cost

2015 Silverado 5.3L Misfire Repair Cost Breakdown (P0206/P0306)

This is a common failure on the 2015 5.3L (L83 engine). The most likely cause is a failed fuel injector on cylinder #6, but diagnostics are critical. Below are the most common repair scenarios.

Critical Note: The P0206 (Injector Circuit) code strongly points to an electrical fault in the injector or its wiring harness. A proper diagnosis should include checking for power, ground, and a pulse signal at the injector connector before replacing parts. The labor times include diagnosis and clearing codes. All prices are estimates; dealer rates will be higher.

Fix

Diagnosis and Repair: 2015 Silverado 5.3L P0206 & P0306 Misfire

As a master technician, I can tell you this is a classic combination of codes on the GM 5.3L EcoTec3 (L83 engine). P0206 indicates an injector circuit fault specifically for cylinder 6. P0306 confirms a misfire on that same cylinder. This strongly points to an electrical issue with the fuel injector or its circuit, not a mechanical problem like a bad coil or plug.

Technical Details & Diagnostic Path

Cylinder 6 is on the driver’s side, second from the front. The system uses a direct injection fuel pump and high-pressure fuel rail, but the injector control is via the Engine Control Module (ECM).

1. Safety First: Disconnect the battery. You will be working near the high-pressure fuel rail. The fuel system must be depressurized via the Schrader valve on the driver’s side fuel rail (cover with a rag).
2. Initial Inspection: Remove the engine cover and the beauty cover over the intake manifold. Visually inspect the injector harness connector at cylinder 6 (gray connector) for damage, corrosion, or pushed-out pins.
3. Circuit Test: With a digital multimeter, check resistance at the injector itself (disconnected). Specification is 0.5 – 2.0 ohms at 20°C (68°F). A reading of infinite ohms (OL) confirms a failed injector. Also check for short to ground or power in the harness.
4. Swap Test (Caution): You can swap the injector with another cylinder (e.g., cylinder 8). If the misfire and code follow to the new cylinder, the injector is faulty. Note: This requires new upper and lower injector seals for any injector you remove.

Most Likely Repair & Parts

The most common fix is replacing the fuel injector. The OEM GM injector part number is 12674590. List price is approximately $220-$260 per injector. You must also use a GM seal kit (part number 12674592), which includes the necessary upper and lower seals and copper gasket, costing about $25-$35.

Critical Procedure: When installing the new injector, you must lubricate the new seals with clean engine oil and ensure they are fully seated. The injector should click into the fuel rail. Improper installation will cause a fuel leak.

Labor & Final Steps

Book time for this repair is approximately 1.5 to 2.0 hours. After replacement, clear codes and perform an ECM fuel injector trim learn procedure with a capable scan tool. Road test to confirm the misfire is resolved.

Important Note: Do not ignore the circuit code. If a new injector doesn’t fix it, you may have a wiring harness issue or a rare ECM driver fault, requiring further diagnosis of the control circuit from the ECM (connector X1, pin 73).

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