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Jeep Renegade Replace Ignition Coil And Spark Plug To Fix DTC P0303

Published on January 8th, 2024

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This article outlines the procedures to fix the cylinder 3 misfiring issue for Diagnostic Trouble Code (DTC) P0303 on the 2017 Jeep Renegade.


The 2017 Jeep Renegade might may symptoms including difficulty starting or cranking but not starting, rough idle, poor acceleration, and an illuminated Malfunction Indicator Light (MIL).

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Innova Scan Tool indicates DTC P0303

The Innova Scan Tool indicates the presence of DTC P0303. which is a crucial code associated with misfiring. Some common factors that can trigger DTC P0303 include:

  • Engine vacuum leak
  • Faulty fuel injector
  • Poor fuel quality or high ethanol level
  • Crankshaft position sensor (CKP) or tone wheel issues
  • Faulty ignition coil or spark plug
  • Coolant leaking into a cylinder
  • Blown cylinder head gasket
  • Low compression
  • Worn camshaft lobes, springs or rocker arms
  • Faulty Powertrain Control Module (PCM)

This article provides information and instructions to assist in identifying the cause of a misfiring issue and resolving DTC P0303 on a 2017 Jeep Renegade.

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Table header 0Step

Time required (hour)

ModelPart numberPart name
2017 Jeep Renegade68242286AB
Ignition Coil

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

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Diagnostic Procedures:

Step 1 - Perform a visual inspection of engine components

Inspect the ignition coil wire(s) or connector(s) to ensure they are securely attached to the spark plugs.

Make sure the coil(s) and housing fit properly into the valve cover, cylinder head, and spark plug(s).

Check the ignition coil harness connector(s) for proper fit into the connector(s) and holders. This will prevent short to voltage, short to ground, or interference with other wires.

While the engine is running at idle, spray a fine water mist onto the wires and coil(s) and observe for evidence of arcing or changes in RPM. Occasionally, fuel contamination may occur, and when the fuel level is low, the dirt or contamination can enter the fuel injection system.

If problems are observed, repair and retest before proceeding.

If no problems are found, proceed to step 2.

Step 2 - Check ignition coil operation.

Remove the ignition coil, spark plug wire, and connector from cylinder #3.

Turn the ignition off and install a spark tester on the ignition coil or ignition wire. Crank the engine observe the spark coming from the spark tester.

A crisp blue spark that jumps the gap of the spark tester should be generated. Is good spark present?

  • Yes - Proceed to step 4 to inspect the spark plug.
  • No - Proceed to step 3 to inspect the ignition coil control circuit.

Step 3 - Check the ignition coil control circuit.

Use a suitable VOM to measure the resistance of the Ignition Coil Control circuit for cylinder 3 between the Ignition Coil harness connector and the PCM harness connector.

Is resistance less than 3.0 Ohms?

  • Yes – Check the PCM for any problems. Replace or Repair as necessary.
  • No - Repair the Ignition Coil Control circuit for an open circuit or high resistance, then proceed to step 6.

Step 4 - Check the spark plug for proper operation.

Turn the ignition off. Exchange the cylinder 3 spark plug with a known good plug from a cylinder that was not indicating a misfire.

Use the Scan Tool to clear DTC(s) and Freeze Frame data. Start and run the engine for a few minutes.

Turn the ignition off and use the Scan Tool to check for DTCs.

Did the misfire switch to the previously good cylinder? Did a misfire DTC set for the previously good cylinder?

  • Yes - Replace the cylinder 3 spark plug, then proceed to step 6.
  • No - Proceed to step 5 to check the Manifold Absolute Pressure (MAP) sensor.

Step 5 - Check the MAP sensor voltage.

Start and run the engine. Use a suitable VOM to monitor the MAP sensor signal voltage.

With the engine idling in neutral or park, snap the throttle. MAP sensor signal voltage should change from less than 2.0 volts at idle to greater than 3.5 volts at wide open throttle.

Does MAP sensor voltage change as specified?

  • No - Inspect for short circuits, open/high resistance, and replace if necessary, then proceed to step 6.
  • Yes - Replace the cylinder 3 ignition coil, spark plug wire, and, or connector(s), then proceed to step 6.

Step 6 - Validate the repair.

Confirm the repair using one of the following procedures:

  • Conduct Key ON Engine Off (KOEO) and Key ON Engine Running (KOER) tests
  • Perform the drive cycle requirements for the fault area.
  • Optionally, operate the vehicle within the conditions recorded in the Freeze Frame data when DTC P0303 was initially set.

Check for pending or stored DTCs. If none are found, the repair is complete.

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