Chevrolet Silverado Replace Spark Plug Wires And Spark Plugs To Fix DTC P0307

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Purpose:

To guide you through the procedure to check Diagnostic Trouble Code (DTC) P0307 and replace spark plug wires and spark plugs to resolve DTC P0307.

Introduction

If the Check Engine Light or Malfunction Indicator Lamp (MIL) is illuminated on the dashboard and the Engine Control Module (ECM) stored DTC P0307, you will examine misfiring cylinders in the car. This article will help you diagnose a DTC P0307 code and replace spark plug wires and spark plugs to fix this code on a Chevrolet Silverado.

P0307: Cylinder 7 Misfire Detected - This means the No. 7 cylinder is misfiring. A misfire may damage the three-way catalytic converter and cause the MIL to blink immediately.

Symptoms of this fault are:

• Check Engine Light ON or flashing
• Misfiring or Stalling
• Rough Idle
• Car Won’t Start or Rough Start
  
• Poor Fuel Economy
  

Possible causes of this fault are:

• Faulty spark plug(s) or wire(s)
• Faulty coil
• Faulty oxygen sensor(s)
• Faulty fuel injector
• Faulty catalytic converter(s)
• Poor compression

With P0307 on a 2014 - 2019 Chevrolet Silverado V8-5.3L, replacing the spark plug wires and spark plugs may resolve this concern.

(This image is for illustrative purposes only and may not match the actual part number)

Diagnostic Procedures:

Before you begin replacing the spark plug(s), you'll need to inspect the ignition coil wire(s), spark plug wire(s) or connector(s) to ensure they fit tightly on the spark plugs.

• Ensure the coil(s) and housing properly fit into the valve cover, cylinder head, and spark plug(s). In addition, check the ignition coil harness connector(s) for proper fitment into the connector(s) and holders. This will prevent a short to voltage, short to ground, etc., or interference to other wires.
• With the engine idling, you may try spraying a fine mist of water across the wires and coil(s), looking for arcing and/or RPM change. There are rare cases where fuel contamination has occurred and, during low fuel level periods, this dirt or contamination is fed into the fuel injection system. Refer to the Vehicle Emissions Warranty Manual for time and mileage coverage for the emissions-related fault(s).

Step 2

Remove the valve rocker arm cover insulator, then remove the spark plug wire, spark plug and/or connector from the No. 7 cylinder, and measure the secondary resistance (332 to 460 Ohms per 25.4 mm, replace if out of spec), and move them to another cylinder(s).

Step 3

Clear DTC(s) and Freeze Frame (FF) information, and perform the verification test.

Step 4

If a DTC is set for the cylinder where the spark plug wire and/or spark plug was moved, replace the spark plug wire and/or spark plug.

Step 5

Repair validation:

• Start the engine, allow the engine to reach operating temperature, and turn off accessories.
• Drive the vehicle within the operating parameters found in the FF data.
• Bring the vehicle to a stop and idle for 2 minutes.
• Use a scan tool to check for pending or stored DTCs. If none are found, the repair is complete.

Replace the spark plug procedure: 

Ensure that the engine is cooled completely before removing the old spark plugs. Adjust the new spark plugs to the proper gap, and do not over-tighten the spark plugs. Inspect the spark plug wire for damage and replace it if necessary.

• Step 1: Remove the spark plug wire from the spark plug.
• Step 2: Loosen the spark plug by 1 or 2 turns.
• Step 3: Clean the spark plug. Remove any dirt from the spark plugs with the brush or use compressed air.

Installation Procedure:

• Step 1: Use your hand to thread the spark plug into the spark plug hole. Turn it about 2 turns clockwise.
• Step 2: Tighten the spark plug carefully and don’t over-tighten the spark plug.Torque: 15 ft-lb (20 Nm)
• Step 3: Install the spark plug wire onto the spark plug

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