EVAP System → Pressure Sensor → Low Input |

P0452 can be described as a generic OBD II Code, meaning it is applicable to all vehicles.

The Evaporative Emission Control System (EVAP) transports the fuel vapors from fuel tanks to intake manifolds to be burnt off.  

The P0452 gas is produced when the system pressure drops too low.

P0452 is not considered to be a break-down risk If it is your only code.

A bad gas cap is often the cause of P0452

The symptoms

Sometimes, more than not It is unlikely that P0452 will be associated with any visible symptoms.  

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

The causes

Below are some common causes for P0452.

• Capacity for gas is not required
• Wiring or bad fuel tank pressure sensor
• Canister clogged with charcoal
• Leakage of vacuum
• Failure to purge the solenoid of EVAP

Diagnostic Procedure

Every vehicle is different, but here’s a solid order of diagnosis when dealing with P0452:

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. The Gas Cap

The fuel tank pressure sensor detected that fuel tank pressure is too low and issued P0452.  This code is generated if the gas cap on your tank isn't tight enough or if you don't have a seal.

Take off the fuel cap.  You should pay attention to how the rubber ring fits into the fuel inlet.  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.

Make sure there is nothing blocking 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.

An OBDII scanner is used by mechanics to measure the fuel tank pressure and determine if the tank has vacuum.

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.

4. EVAP System Questions

An error in the EVAP can lead to P0452.  Here’s how a good mechanic would You can diagnose it.  This video is worth watching if you want to tackle it yourself.

A Common Diagnostic Mistake

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.

Conclusion: P0452

Bad gas caps are more common than you might think.  This code can sometimes be difficult to diagnose if your gas cap works fine.