A P1247 on the 7.3L Power Stroke indicates turbocharger boost pressure is lower than expected, so the engine is not making the boost the computer commands.
What P1247 means
Turbocharger Boost Pressure Low is a diagnostic trouble code set when the monitored value falls outside its expected range. On the 7.3L Power Stroke, it narrows the problem to a specific system, and reading it correctly prevents replacing good parts.
Common causes
- Boost leak in the intake or intercooler plumbing
- Wastegate or turbo problem
- Failing boost (MAP) sensor
- Restricted intake or exhaust
Symptoms you may notice
- Low power and sluggish acceleration
- Excess smoke under load
- Check-engine light
- Poor towing performance
How to diagnose it
Check for boost leaks in the charge-air plumbing and intercooler first, since they are common. Compare commanded versus actual boost, and inspect the wastegate and turbo. A leak or a stuck wastegate produces low boost even with a healthy turbo.
How to fix it
Repair boost leaks and address the wastegate or turbo as needed, and replace a faulty boost sensor if it is misreporting. Confirm the intake and exhaust are not restricted. Verify boost recovers after the repair.
Frequently asked questions
What causes low boost on a 7.3L?
Boost leaks in the plumbing, a wastegate or turbo problem, or a faulty boost sensor. Check for leaks first.
Is the turbo bad?
Not necessarily. A boost leak or stuck wastegate causes low boost even with a healthy turbo, so inspect the plumbing.
Will it hurt towing?
Yes. Low boost means low power under load, so it is worth fixing before towing.
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