Dodge Ram P0452 - FUEL tank pressure low diagnosis

Dodge Ram's OBD II can detect P0452.  It means that your Ram’s EVAP system has detected low fuel tank pressure.

The fuel vapors are sent from the tank to the intake to be burnt off by the evaporative emissions controller system (EVAP).  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

Your Ram should continue running normally, even if P0452 presents with no noticeable symptoms.

Below are some common symptoms of this code.

• Check engine light (obviously)
• A smell of fuel indicates that there is a leak in the fuel tank or loose fuel cap.
• Hessing sounds (signals a vacuum leak)

Dodge Ram

Below are the top causes of P0452 for Dodge Rams.

• Gas cap loose
• Wiring or bad fuel tank pressure sensor
• Canister of charcoal clogged
• Vacuum leak
• Failure to purge the solenoid of EVAP

Dodge Ram P0452 Diagnostic Procedure

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

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 Ram’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.  A replacement will likely be required if the rubber ring is worn or dry-rotted.

OBDII code codes remain in the system until the issue is resolved.  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. Verify the fuel pressure readings

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 Ram’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

Failures in the EVAP can result in P0452.  Here’s how a good mechanic would go about diagnosing it.  If you're going to attempt this task yourself, it is well worth the effort.

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 Ram while you tighten the gas cap and replace it. This will allow the code to clear before proceeding with your diagnosis.

Dodge Ram P0452 Conclusion

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