Low Boost Pressure
The boost pressure is lower than expected during operation.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine isn't getting enough air boost from the turbo or supercharger, which means it's not making as much power as it should.
What the computer is actually seeing
The ECM is monitoring the boost pressure sensor, expecting values typically ranging between 10 to 30 psi during acceleration. If the signal drops below a set threshold (like 5 psi), it triggers this code.
What a healthy reading looks like
Expected boost pressure should be between 10-30 psi depending on engine load and speed; anything significantly lower can trigger this code.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connectors of the boost pressure sensor for damage or corrosion. If damaged, repair or replace. If okay, proceed to step 2.
- 22. Check for vacuum leaks in the intake system. Use smoke testing or spray soapy water to find leaks. Fix any leaks found. If no leaks, move to step 3.
- 33. Measure the boost pressure using a reliable gauge. Compare the measured value to the expected values (10-30 psi). If it’s low, proceed to step 4. If it's okay, suspect a faulty ECM or sensor.
- 44. Inspect the turbocharger/supercharger for proper operation and play in the shafts. If you find issues, repair or replace the affected component.
Common causes
- Faulty boost pressure sensor
- Vacuum leaks in intake system
- Turbocharger or supercharger malfunction
- Exhaust restrictions
- Wiring issues or connectors for the boost pressure sensor
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally okay to drive short distances, but expect reduced power. Fix it when you can to avoid engine strain.
Will this code come back after clearing?
If the underlying issue isn't resolved, yes, it will often return after clearing the code.
Why does this code pair with SPN 765?
SPN 765 indicates high pressure, and when it's low (SPN 766), it often points toward similar issues in the boost system.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →