Fuel Pressure - Low
The engine control unit has detected low fuel pressure.
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What it means (plain English)
The engine is not getting enough fuel pressure from the pump to run properly, usually less than 50 psi when it should be above that.
What the computer is actually seeing
The ECM expects fuel pressure to be higher than 50 psi during operation; any reading below that triggers this fault.
What a healthy reading looks like
Normal fuel pressure should be between 50 psi and 65 psi, depending on the engine specifications.
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. Check the fuel level in the tank. Top off if it's low. -> If low, fill tank and retest code.
- 22. Inspect fuel lines and connections for leaks. Fix any leaks found. -> If leaks present and repaired, retest code.
- 33. Check the fuel filter for clogs. Replace if necessary. -> If clogged and replaced, retest code.
- 44. Measure the fuel pressure using a gauge. Compare it with expected values. -> If below 50 psi, continue checking pump and regulator.
- 55. Test the fuel pump operation voltage at the connector. Should be at least 12 volts while cranking. -> If less than 12 volts, inspect wiring and fuse. If voltage OK, replace the pump.
- 66. Test the fuel pressure regulator for proper operation. Disconnect the vacuum line and monitor fuel pressure. -> If pressure rises above 65 psi, regulator is faulty.
Common causes
- Clogged fuel filter
- Weak fuel pump
- Leaking fuel lines or connections
- Faulty fuel pressure regulator
- Electronic control unit issue
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with SPN 71 active?
It's not safe; low fuel pressure can cause engine stalling or performance issues.
Will the code come back if I clear it?
Yes, if the underlying issue isn't fixed, the code will likely return.
Why does this code often pair with SPN 91?
SPN 91 indicates fuel temperature issues, which can coincide with low fuel pressure caused by poor pump performance.
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