Question about 2002 Jeep Wrangler
THE P0455 CODE POSSIBLE CAUSES ARE
On 2.5L 4 cylinder engines, a fitting on drivers side of cylinder head (valve) cover contains the metered orifice. It is connected to manifold vacuum.
A fresh air supply hose from the air cleaner is connected to front of cylinder head cover on 4.0L engines. It is connected to rear of cover on 2.5L engines.
When the engine is operating, fresh air enters the engine and mixes with crankcase vapors. Manifold vacuum draws the vapor/air mixture through the fixed orifice and into the intake manifold. The vapors are then consumed during combustion.
The duty cycle EVAP canister purge solenoid (DCP) regulates the rate of vapor flow from the EVAP canister to the intake manifold. The Powertrain Control Module (PCM) operates the solenoid.
During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.
The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the PCM cycles (energizes and de-energizes) the solenoid 5 or 10 times per second, depending upon operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time that the solenoid is energized. The PCM adjusts solenoid pulse width based on engine operating condition.
FUEL FILLER CAP
The plastic fuel tank filler tube cap is threaded onto the end of the fuel fill tube Certain models are equipped with a 1/4 turn cap.
The loss of any fuel or vapor out of fuel filler tube is prevented by the use of a pressure-vacuum fuel fill cap. Relief valves inside the cap will release fuel tank pressure at predetermined pressures. Fuel tank vacuum will also be released at predetermined values. This cap must be replaced by a similar unit if replacement is necessary This is in order for the system to remain effective.
CAUTION: Remove fill cap before servicing any fuel system component to relieve tank pressure. If equipped with a California emissions package and a Leak Detection Pump (LDP) , the cap must be tightened securely. If cap is left loose, a Diagnostic Trouble Code (DTC) may be set.
LEAK DETECTION PUMP
The Leak Detection Pump (LDP) is used only with certain emission packages
The LDP is a device used to detect a leak in the evaporative system.
The pump contains a 3 port solenoid, a pump that contains a switch, a spring loaded canister vent valve seal, 2 check valves and a spring/diaphragm.
Immediately after a cold start, engine temperature between 40 °F and 86 °F , the 3 port solenoid is briefly energized. This initializes the pump by drawing air into the pump cavity and also closes the vent seal. During non-test test conditions, the vent seal is held open by the pump diaphragm assembly which pushes it open at the full travel position. The vent seal will remain closed while the pump is cycling. This is due to the operation of the 3 port solenoid which prevents the diaphragm assembly from reaching full travel. After the brief initialization period, the solenoid is de-energized, allowing atmospheric pressure to enter the pump cavity. This permits the spring to drive the diaphragm which forces air out of the pump cavity and into the vent system. When the solenoid is energized and de-energized, the cycle is repeated creating flow in typical diaphragm pump fashion. The pump is controlled in 2 modes:
Pump Mode: The pump is cycled at a fixed rate to achieve a rapid pressure build in order to shorten the overall test time.
Test Mode: The Solenoid Is Energized With A Fixed Duration Pulse. Subsequent fixed pulses occur when the diaphragm reaches the switch closure point.
The spring in the pump is set so that the system will achieve an equalized pressure of about 7.5 inches of water.
When the pump starts, the cycle rate is quite high. As the system becomes pressurized pump rate drops. If there is no leak the pump will quit. If there is a leak, the test is terminated at the end of the test mode.
If there is no leak, the purge monitor is run. If the cycle rate increases due to the flow through the purge system, the test is passed and the diagnostic is complete.
The canister vent valve will unseal the system after completion of the test sequence as the pump diaphragm assembly moves to the full travel position.
A vacuum schematic for emission related items can be found on the VECI label. Refer to Vehicle Emission Control Information (VECI) Label for label location
The evaporative (EVAP) canister is located in the engine compartment on the left inner fender.
A maintenance free, EVAP canister is used on all vehicles. The EVAP canister is filled with granules of an activated carbon mixture. Fuel vapors entering the EVAP canister are absorbed by the charcoal granules.
Fuel tank pressure vents into the EVAP canister. Fuel vapors are temporarily held in the canister until they can be drawn into the intake manifold. The duty cycle EVAP canister purge solenoid allows the EVAP canister to be purged at predetermined times and at certain engine operating conditions.
ONE WAY TO CLEAR ENGINE CODES WITH OUT HAVING A DIAGNOSTIC COMPUTER IS UN PLUG THE BATTERY AND LEAVE IT SIT FOR ROUGHLY 20 MINUTE AND REHOOK UP THIS MIGHT CLEAR THE CODES WITH OUT A COMPUTER.. BUT IF THE PROBLEM ISN'T FIXED THE CODES WILL SHOW AGAIN..
HOPE THIS HELPS
Posted on Nov 14, 2010
In the case of evaporative emission systems leak codes P0442 and P0455 (small and large leak) it is nearly impossible to know what leaking and causing the codes without using a special piece of equipment called a smoke leak detector, smoke is injected into the evaporative control system and then you look smoke escaping, the machines are very expensive but worth every penny, if no leaks are found after doing the smoke tests you can assume that the pressure sensor that is on the top of the fuel tank is defective, this gives the PCM (Powertrain Control Module) a false reading and that is interpreted as a leak which generates the codes. So in closing my advice to you is have a shop run the leak detection test with the smoke machine, it is worth every penny, it is doubtful without this test that you will easily find the leak if that is the problem, the test is not that expensive to have run, call around for estimates, thy can vary widely. Have a good day.
Posted on Nov 14, 2010
SOURCE: 2002 wrangler 4.0 6 cylinder
Here is a picture of the canister and all the other parts.Let me know if this worked for you.One other thing is if you have a leak taping it will not keep it from leaking.You will have to replace the part that is leaking or not working properly.Let me know how this picture works out.This is the first time I have tried this.Good luck and thanks for using fixya.
Posted on Nov 13, 2010
Tips for a great answer:
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Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
Otherwise, replace the gas cap, and/or
Inspect the EVAP system for cuts/holes in tubes/hoses (you may hear a vacuum noise or smell fuel), repair if necessary
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