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Service bulletins for the 2021 Jeep Grand Cherokee L

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

214 on file from NHTSA, as of 2026-10-19.

About P0304 on the 2021 Jeep Grand Cherokee L: what the code means, and the bulletins and recalls about the same components.

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Only bulletins with trouble code: P0304 are shown. Show all

Bulletins, newest first
18-050-262026-04-22. Service bulletin. POWER TRAIN; ENGINE. Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must SYMPTOM: exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): ● P0300 - Multiple Cylinder Misfire - In Active or Stored status set during cold start catalyst heating. ● P0301 - Cylinder 1 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0302 - Cylinder 2 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0303 - Cylinder 3 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0304 - Cylinder 4 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0305 - Cylinder 5 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0306 - Cylinder 6 Misfire - In Active or Stored status set during cold start catalyst heating. Customers may also comment on one or more of the following: ● Check engine illuminates when fueling the vehicle while the engine is running. ● Vehicle has a noticeable misfire. ● Vehicle idles rough. ● Engine noise. NOTE: Noise is heard coming from the valvetrain. In addition, the following software enhancement is available: ● Update to prevent customers from driving their vehicles while the Electric Park Brake (EPB) is engaged. Engine torque will be limited to prevent the Rear Drive Unit from being damaged. NOTE: Previously, the EPB would remain engaged without any torque limit which could lead to the Rear Drive Unit being damaged/broken. This bulletin involves reprogramming the PCM with the latest available software.
09-011-252025-05-20. Service bulletin. ENGINE. "Misfire Diagnostic Trouble Codes (DTCs), Rough Idle, Valvetrain Noise Customers may experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle may exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): ● P0301 - Cylinder 1 Misfire. ● P0302 - Cylinder 2 Misfire. ● P0303 - Cylinder 3 Misfire. ● P0304 - Cylinder 4 Misfire. ● P0305 - Cylinder 5 Misfire. ● P0306 - Cylinder 6 Misfire. Customers may comment on one or more of the following: ● Rough idle. ● Valvetrain noise. "

The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.