What causes P0300 on a Jeep Grand Cherokee?

Common causes of P0300 on Jeep Grand Cherokee: Ignition coil failure on 3.6L Pentastar V6 (Grand Cherokee/Cherokee); Spark plug thread damage from aluminum head over-torque on 3.6L Pentastar; Rocker arm roller follower failure causing loss of valve actuation (TSB 09-002-14 REV. 9); Exhaust manifold crack causing exhaust leak and O2 sensor misreading on 3.6L; Fuel injector deposit buildup on 3.6L causing lean misfire on individual cylinders.

P0300

P0300 Jeep Grand Cherokee

Q: How much does it cost to fix P0300 on a Jeep Grand Cherokee?

Fixes for P0300 on Jeep Grand Cherokee include: Replace all 6 ignition coils with Mopar OE and new Champion spark plugs, Replace spark plugs carefully at 12 lb-ft torque and use anti-seize on threads, Replace all rocker arm assemblies with updated Mopar roller followers (recall/TSB coverage), Replace cracked exhaust manifold with updated Mopar casting, Clean fuel injectors professionally or replace with Mopar OE injectors.

Random/Multiple Cylinder Misfire Detected · Powertrain Code · High · Repair: Moderate

What is P0300?

The ECM has detected misfires occurring in multiple or random cylinders. Common causes include worn spark plugs, faulty ignition coils, vacuum leaks, low fuel pressure, or a failing catalytic converter.

When the Jeep Grand Cherokee triggers code P0300 (random/multiple cylinder misfire detected), it typically points to an issue in the powertrain system. This is a high severity code, so address it promptly to avoid further damage or safety concerns. Below you'll find the most common causes, symptoms, and repair options specific to the Jeep Grand Cherokee.

This repair is rated moderate, meaning some experience and specialty tools required.

Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Jeep Grand Cherokee.

Common Causes on Jeep Grand Cherokee

Ignition coil failure on 3.6L Pentastar V6 (Grand Cherokee/Cherokee)
Spark plug thread damage from aluminum head over-torque on 3.6L Pentastar
Rocker arm roller follower failure causing loss of valve actuation (TSB 09-002-14 REV. 9)
Exhaust manifold crack causing exhaust leak and O2 sensor misreading on 3.6L
Fuel injector deposit buildup on 3.6L causing lean misfire on individual cylinders

Symptoms

Rough idle with noticeable engine vibration
Engine shaking or stumbling under load
Loss of power during acceleration
Check engine light flashing intermittently
Poor fuel economy
Hesitation or stumble on acceleration

Recommended Fixes

Replace all 6 ignition coils with Mopar OE and new Champion spark plugs

Replace spark plugs carefully at 12 lb-ft torque and use anti-seize on threads

Replace all rocker arm assemblies with updated Mopar roller followers (recall/TSB coverage)

Replace cracked exhaust manifold with updated Mopar casting

Clean fuel injectors professionally or replace with Mopar OE injectors

Notes for Jeep Grand Cherokee

The 3.6L Pentastar rocker arm issue can cause a single cylinder misfire that progresses to multiple.

P0300 Jeep Grand Cherokee

What is P0300?

Common Causes on Jeep Grand Cherokee

Symptoms

Notes for Jeep Grand Cherokee

Check Jeep Grand Cherokee Specs