Ford Fiesta P0452: Low FUEL Tank Pressure Diagnosis

A generic OBD II Code, P0452 may be present in your Ford Fiesta.  It means that your Fiesta’s EVAP system has detected low fuel tank pressure.

Evaporative emissions control systems (EVAP), send fuel vapors to the intake to be burnt off.  The system generates P0452 if the pressure gets too low.

If P0452 is your only code, it should not be considered as a breakdown threat. It is most often fixed by changing the fuel cap.

A bad gas cap is often the cause of P0452

The symptoms

P0452 will not usually be associated with any visible symptoms. Fiestas will continue running fine.

These are the most common symptoms associated with this code.

• Check engine light (obviously)
• You can smell fuel, which indicates a loose fuel cap (or EVAP leak).
• A hissing sound is an indication of a vacuum leak

Ford Fiesta P0452: Causes

These are the most common reasons for P0452 in Ford Fiesta.

• Gas cap loose
• Low fuel tank pressure sensor, or wiring
• Charcoal canisters that are clogged
• Leakage of vacuum
• Failure of the EVAP purge solenoid

Ford Fiesta P0452 Diagnostic Procedure

Here’s a solid order of diagnosis when dealing with P0452 in your Fiesta:

1. You can also check for additional codes

Skip to next section if P0452 is your only trouble code.  If it is not, cross referencing the other code’s causes with the common causes of P0452 can really help you eliminate some possibilities.

2. Seek out the gas cap

P0452 indicates that your Fiesta’s fuel tank pressure sensor has detected that the pressure in the fuel tank is too low.  This code is caused by a gas cap that isn't tight enough or not sealing well.

Take off the fuel cap.  The rubber ring should fit snugly to the fuel intake.  It is possible to replace P0452 if it has become dryrotted or is damaged.

OBDII codes can remain in your system even after you have fixed the problem.  If you believe that the fuel cap was loose, or you changed it, you’ll need to clear the code with a code scanner and see if it comes back or not.

You should also ensure that there are no obstructions to the fuel inlet.  If it has gunk built up or mud on it, you’ll need to use a wet rag or some WD-40 to clean it off.

If it does come back, we’ll need to move on to the next step.

3. Take fuel pressure measurements

It is difficult to diagnose P0452 outside of the obvious: check the gas cap.

A mechanic would use a professional OBDII scanner to check the fuel tank pressure readings from your Fiesta’s fuel tank to see if there is vacuum in the tank.

If it doesn’t look right, the wiring to the fuel pressure sensor would need to be inspected.  

If that doesn’t help anything, the tank pressure sensor itself would need to be replaced.

If everything looks fine, they’d move on to checking the EVAP system.

4. EVAP System Questions

An EVAP failure can lead to P0452.  Here’s how a good mechanic would go about diagnosing it.  This video is worth watching if this is something you want to tackle yourself.

The Common Diagnostic Error With P0452

People make the common error of diagnosing P0452 by doing anything without checking the gas cap.  

Or, they’ll keep going on with the diagnostic process after addressing the fuel cap because they did not clear their trouble codes.

You can then drive the Fiesta for several minutes to verify that the code is clear before you move on with your diagnosis.

Ford Fiesta (P0452) Conclusion

A bad gas cap is the most common reason for P0452.  This code can sometimes be difficult to diagnose if your gas cap works fine.