Some Mazda vehicles (2010 Mazda3 and Mazdaspeed3 with VINs lower than JM 1BL…..374449, produced before August 17, 2010; and 2010 CX-7 with VINs lower than JM3ER….327446, produced before March 1, 2010) may experience a MIL-on with only DTC P0451 stored in memory.
This is caused by water entering and freezing in the atmosphere breather hose of the fuel tank pressure sensor (FTP). For Mazda3, this happens when the vehicle is washed in a high-pressure car wash. For CX-7, this happens when the vehicle is driven on a wet road in freezing temperatures. To correct this problem, a modified breather hose has been adopted.
Remove and inspect both the FTP sensor (A) and atmosphere breather hose (B). Inspect for water and/or ice. End “C” goes to the fuel tank and end “D” goes to the canister. If water is found, drain the water from the FTP sensor by shaking it out. If ice is found, warm-up the sensor and then drain. CAUTION: Do not use pressurized air to drain the water from the FTP sensor, which can damage the sensor.
Install a modified breather hose (B1) as shown in the following illustration.
Reinstall the FTP sensor.
Using the M-MDS, confirm that the FTP sensor PID voltage readings are within 2.5 to 3.6 volts. If the FTP sensor voltage readings are within range, the repair is complete. If the FTP voltage readings are not within range, the sensor has been damaged and must be replaced.
The Mazda part number for the modified breather hose is ZYE9-42-232.