What Does It Mean?
This diagnostic code (DTC) is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996 and newer), although specific repair steps may vary slightly by model.
DTC P0452 is related to a malfunction in the emission system. Your PCM or powertrain control module relies on a fuel tank pressure sensor to detect fluctuations in the internal pressure of the tanks.
Depending on your car’s make, the sensor may be located in the fuel purge line coming from the fuel module at the top of the fuel tank or at the top of the tank itself.
The PCM has determined that the system pressure is abnormally low, indicating a problem in the system, not necessarily only at the sensor. This sensor is used primarily for emission control strategy only. Your fuel tank will tend to create fuel vapor pressure when temperatures are high and a vacuum when under load.
The sensor sends a voltage to the computer for analysis, the current value depends on the pressure or vacuum. The code applies to all vehicles, but they differ in sensor output. For example, the Buick sensor produces about 0.1 volt with positive pressure in the tank and up to 5 volts with negative pressure, as in a vacuum.
A Honda sensor increases the voltage signal as positive pressure builds up in the tank. In both cases, the sensors have the same purpose. They all convert pressure into a voltage that increases or decreases with the decay of pressure or vacuum.
Evaporative emission-related fault codes include P0450, P0451, P0453, P0454, P0455, P0456, P0457, P0458, and P0459.
Symptoms
The only symptom you will notice with a P0452 code is the service engine soon or check engine light will come on. In rare cases, you may smell a noticeable fuel vapor.
Causes
Potential causes of this DTC include:
Faulty fuel tank pressure sensor
Sensor harness has an open or short circuit
Faulty electrical connection to the FTP sensor
Cracked or broken vapor line to the vacuum canister
Cracked or broken positive vapor line to the tank
Pinched line
Leaking seal at the fuel pump module
Gas cap left loose causing vacuum loss
Pinched vapor line
Diagnostic Steps
and Possible Solutions
This issue leaves little to repair due to the sensor’s location and the tools needed to diagnose the problem. The sensor is located on top of the fuel tank in or near the electric fuel pump module.
The first rough action is to check all technical service bulletins for your car. This is always good practice, as they may have recalls. Secondly, you see the type of issues customers face with this model and the recommended corrective action.
Finally, most vehicles have a very long warranty on emission control devices, such as 100,000 miles, so it would be wise to check your warranty and take advantage of it if available.
To access the sensor, the fuel tank must be removed. This is a difficult and somewhat dangerous job that is best left to a technician with a lift.
More than 75 percent of the time, someone did not take the time to “click” the fuel cap closed. When the fuel cap is loose, the tank cannot create a vacuum for purging and vapor pressure does not build up, resulting in low input voltage and the setting of code P0452. Some vehicles are now equipped with a “check fuel cap” light on the dashboard that informs you to tighten your cap.
It is possible to check the vapor hoses coming from the top of the fuel tank under the vehicle to find a broken or crimped line. There are three to four lines coming from the top of the tank leading to the frame rail on the driver’s side that can be checked. But if they need to be replaced, the tank must be lowered.
The technician uses a special diagnostic tool that will test the sensor in the car and all line and tank pressures, corrected for temperature, humidity, and altitude. It will also indicate to the technician if a vapor line is faulty in any way and if the electrical connections are satisfactory.
Other EVAP DTCs: P0440 – P0441 – P0442 – P0443 – P0444 – P0445 – P0446 – P0447 – P0448 – P0449 – P0453 – P0455 – P0456