FMI 9: Engine Fuel Pressure Too Low
The engine control module detects low fuel pressure in the system.
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What it means (plain English)
The computer is seeing that the fuel pressure in the lines is lower than expected, which can lead to poor engine performance because the engine isn't getting enough fuel to run properly.
What the computer is actually seeing
The engine control module expects fuel pressure to be within a specific range, typically between 50-60 psi at idle. When the pressure drops below this threshold, a SPN 6702 code is triggered.
What a healthy reading looks like
Expected fuel pressure values should be between 50-60 psi when running. At idle, it should stabilize around 55 psi.
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 fuel level in the tank to ensure it's not empty. Decision: Is fuel present? Yes: Go to step 2; No: Refill fuel tank and retest.
- 22. Inspect fuel lines and connections for leaks or damage. Decision: Any leaks found? Yes: Repair leaks, clear code, and retest; No: Go to step 3.
- 33. Measure fuel pressure at the rail with a gauge. Decision: Is pressure below 50 psi? Yes: Go to step 4; No: Check for other codes and proceed accordingly.
- 44. Check the fuel pump operation (listen for correct sound and measure voltage to the pump). Decision: Is the pump functioning correctly? Yes: Replace fuel pressure regulator; No: Replace fuel pump.
Common causes
- Clogged fuel filter
- Weak fuel pump
- Leaking fuel lines or injectors
- Faulty fuel pressure regulator
- Air in fuel lines
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to fix it soon; driving with low fuel pressure can cause further engine damage or stalling.
Will this code come back after clearing?
If the underlying issue isn't fixed, expect it to return.
Why is this code paired with low power?
Low fuel pressure means the engine isn't getting enough fuel, causing poor performance and reduced power.
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