P0455/P0442 Leaks: Overview

A. Locate the hose between the canister close valve and the fresh air filter. Slide the hose clamp back and disconnect the hose at the air filter.

B. Insert one end of the "test" hose, about four inches, into the fresh air hose at the canister close valve.

C. Slide a hose clamp over the two hoses.

D. Place HDS in the "DIGITAL RECORD" mode. While watching the DPS signal on HDS, GENTLY begin to blow into the "test" hose (the DPS voltage should begin to rise). Continue to gently blow into the hose until the DPS voltage is approximately 4.0 volts. Do not over pressurize since the sensor cannot read over 4.5 volts. If the voltage does not rise, perform the inspection as described in P0446 Section B to look for a blockage/restriction. After repairing the restriction, return to this section to finish the inspection.

E. Immediately clamp the "test" hose with hose pinching pliers. If the system does not leak, the voltage will remain steady (the value must remain constant +/- 0.05 volts over 10 seconds). A drop in voltage indicates a leak is present. Large leaks can usually be heard at the source of the leak while blowing into the test hose.

F. If the pressure remains constant, remove the hose pinching pliers from the test hose. The system should return to atmospheric pressure in approximately 45 seconds. If it takes longer than 45 seconds, move the "test" hose to the front of the fuel tank and repeat steps D, E and F checking for restricted vapor hoses or internal blockages in the "To Tank" circuit. Use the "Pressurize/Clamp/Observe" method to chase the blockage closer each time to the DPS sensor.

G. If the voltage decreases while the hose pinching pliers are clamped on the "test" hose, repeat steps D and E, and then connect additional hose pinching pliers at the vapor hose located at the front of the fuel tank (just behind the under carriage for Elantra and Tiburon and through the fuel pump access cover for the Accent). If the DPS voltage continues to drop, then the leak is located between the hose pinching pliers and the back of the vehicle. If the voltage remains constant after applying the second hose pinching pliers, then the leak is between the front of the fuel tank and the front of the car.

H. After determining whether the leak is at the front or rear of the car, the leak can be "isolated" by applying the hose pinching pliers at different locations until the source of the leak is found.

I. The evaporative emissions self check must be performed to ensure system integrity.

TIP FOR CODES P0455 AND P0442:





A tip to determine if a P0455 or P0442 code has been successfully repaired (see Graph # 9): immediately after the self check finishes and the canister purge valve begins its normal purge cycle, the engine can be briefly "revved" one time after the canister purge valve begins cycling. After "revving" the engine, watch the canister close valve voltage. If the canister close valve remains at battery voltage for 30 seconds after revving the engine, the system has been properly repaired. If the canister close valve voltage drops to 0 volts and the system performs another self check, then the system has not been successfully repaired and will eventually set a code.