What do P0302 and P0304 together mean?
Quick answer
On the Ford 6.4L diesel application covered by the cited Ford document, P0302 identifies a cylinder 2 misfire record and P0304 a cylinder 4 misfire record. That tells you which cylinders the records name, not why the events occurred or whether those cylinders are physically adjacent. Confirm your exact engine and cylinder layout, then review code status and freeze-frame or event context before drawing conclusions. For another vehicle, verify the code meanings in its applicable service information.
The question, the details, the next step.
What does it mean if my vehicle shows P0302 and P0304 together?
Treat them first as two cylinder-specific misfire records—not as proof that one particular part has failed. For the Ford 6.4L diesel application described in the Ford document, P0302 is labeled cylinder 2 misfire detected and P0304 cylinder 4 misfire detected. That source establishes the cylinder labels for that application; it does not establish that the cylinders are physically adjacent or share a cause. [S1]
So the useful first question is not “Which part do I replace?” It is “Do these definitions apply to my exact engine, and what was happening when each code was recorded?”
Can I assume cylinders 2 and 4 are next to each other or that one fault affects both?
No—not from this code pair alone. Cylinder numbering and physical layout depend on the exact engine, so check the applicable service information rather than inferring location from the numbers. Ford’s cited document specifically says its labels do not establish physical adjacency or a shared cause. [S1]
A pair of codes is a clue to organize diagnosis, not a verdict on a failed component. Avoid choosing a replacement part solely because both codes appeared together. A qualified technician can compare the engine-specific layout with the codes’ status and recorded operating context.
What details should I gather before I arrange a diagnostic check?
Write down the year, make, model, and exact engine designation, if known. Record whether each code is current, pending, or stored as reported by the scan tool, and save available freeze-frame or event information before clearing anything. The cited Ford guidance recommends confirming the engine and cylinder layout and comparing code status and freeze-frame/event context. [S1]
Also note when you first saw the codes and any relevant change you observed, such as when the warning appeared or whether it returned after a restart. Keep observations separate from guesses about the cause. Don’t attempt hazardous tests; provide the information to a qualified diagnostic professional.
How should I ask for the check, and what would a useful handoff look like?
Prioritize the questions this way: first, ask the professional to verify the code definitions and cylinder numbering for your exact engine. Next, ask them to review the status and freeze-frame or event context for both records. Finally, ask what further checks are appropriate under the vehicle’s service information and what evidence supports any repair recommendation. The cited source does not identify the cause of these codes, prescribe a repair, or show that the two records share one cause. [S1]
Copy and complete this handoff:
“Vehicle: [year, make, model]. Engine: [exact designation, if known]. Codes: P0302 [status]; P0304 [status]. Freeze-frame/event details available: [yes/no; attach or summarize]. Codes first noticed: [date or circumstances]. Observations: [what you saw, without a suspected diagnosis]. Please confirm the code definitions and cylinder layout for this engine, review the recorded context, and explain what diagnostic checks support any repair recommendation.”
If the engine or code status is unknown, say so rather than filling in a guess.
A practical checklist
Record the vehicle’s year, make, model, and exact engine designation if known.
Verify both code definitions and cylinder numbering in service information for that engine.
Note each code’s scan-tool status; do not assume both records have the same status.
Save available freeze-frame or event context before clearing codes.
Write down when the codes appeared and relevant observations, separating facts from suspected causes.
Ask a qualified professional to explain what evidence supports any proposed repair.
A few more useful answers
Do P0302 and P0304 prove one shared fault?
No. The cited source identifies cylinder-specific records for its covered Ford application but does not establish a shared cause. The vehicle’s exact engine and recorded context need to be checked.
Does this code interpretation apply to every vehicle?
The cited definitions are for the covered Ford 6.4L diesel application. Confirm the meanings for your exact vehicle and engine using applicable service information.
Should I replace a part based only on this code pair?
No. The code pair alone does not identify a failed part. Ask for an engine-specific diagnostic check and an explanation of the evidence behind any repair recommendation.
Sources
References used for this guide.
- [S1] Ford 6.4L Diesel OBD System Operation Summary: Misfire Monitor fordservicecontent.com · Checked