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QUESTION: i have a po449 code and wonder what is the best thing to do first and if that could have anything todo with gas in engine oil

ANSWER: Ike,

The PCM has determined that a malfunction exists in the electrical circuit for the vent valve/solenoid in the evaporative emission control system.

Definition:
EVAP (Evaporative Emission System) purge/vent solenoid circuit condition

Explanation:
The solenoids and system wiring are monitored for opens or shorts

Probable Causes
1- Purge or vent solenoids defective
2- Check connector and wiring
3- Fuel saturated vapor canister
4- Failed EVAP vent solenoid

Here is a site that explains this malfunction:
http://www.obd-codes.com/p0449

There is a possibility that this problem can cause gas in the oil.

Carl

---------- FOLLOW-UP ----------

QUESTION: i read that it could be the thank pressure sensor what is that suppossed to read and the volts on that too

Answer
Ike,

OBD II Fault Code
   OBD II P0451

Fault Code Definition

   Evaporative Control System Pressure Sensor Range/Performance

What does this mean? The Code P0451 indicates that the Evaporative Pressure Sensor is indicating pressure change values that are not within specification, during the EVAP Monitor test and/or the operation of the vehicle.

The evaporative control (EVAP) system captures any raw fuel evaporating from the fuel storage system (e.g. the fuel tank, filler neck, and fuel cap). Under precise operating conditionsódictated by engine temperature, speed, and loadóthe EVAP system stores and purges these captured fuel vapors back into the combustion process. The Fuel Tank Pressure Sensor is a device that tracks any positive or negative pressure changes in the Fuel Storage or Evaporative Control (EVAP) system. It constantly relays this pressure information to the Powertrain Control Module (PCM). The Fuel Tank Pressure Sensor is located on top of the Fuel Tank, or on or near the Fuel Pump and Fuel Gauge Module.

Symptoms

   Check Engine Light will illuminate
   In most cases, there are no adverse conditions noticed by the driver
   In some cases, there may be a noticeable fuel odor caused by the release of fuel vapors

Common Problems That Trigger the P0451 Code

   Defective Fuel Tank Sending Unit
   Defective or damaged Fuel Tank
   Defective Fuel Tank Pressure Sensor, wiring, or computer
   Defective Carbon Canister
   Defective Canister Vent Valve - in some cases

Common Misdiagnoses

   Fuel Cap
   Evaporative Purge Valve
   Evaporative Vent Valve

Polluting Gases Expelled

   HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog

The Basics
The Fuel Tank Pressure Sensor is a device that tracks any positive or negative pressure changes in the Fuel Storage or Evaporative Control (EVAP) system. It constantly relays this pressure information to the Powertrain Control Module (PCM). The Fuel Tank Pressure Sensor is located on top of the Fuel Tank, or on or near the Fuel Pump and Fuel Gauge Module.

P0451 Diagnostic Theory

The Evaporative Control System Pressure Sensor Range/Performance code sets when the readings of the Pressure Sensor are irrational and/or out of range for ten seconds of vehicle operation after a cold start. This code uses "two trip" logic, which means that the fault condition must be present during two successive cold starts and vehicle operation.

Common Tests for the Evaluating the Fuel Tank Pressure Sensor

   Retrieve the code and write down the freeze frame information to be used as a baseline to test and verify any repair.
   Pay very close attention to the Fuel Tank Pressure readings by observing its data stream on a scan tool. Does the Fuel Tank Pressure Sensor work properly? If it doesn't, the system will think that no vacuum is being created when, in fact, there is a vacuum being created that the Fuel Tank Pressure Sensor is unable to read. The Fuel Tank Pressure Sensor is the primary feedback sensor that the Powertrain Computer relies on for the leak test data.
   Inspect and test the Fuel Pressure Sensor wiring. Verify that there is a 5-volt reference signal from the PCM, a good ground, as well as a good signal return circuit to the PCM.
   While observing the data stream change (or lack there of) on a scan tool, test the Pressure Sensor with a Vacuum Gauge while it is connected to the wiring harness.
   If all of the above test results are within spec, then the problem may reside in the PCM itself.

Carl

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Carl Brandt

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Will discuss suspensions, lifts, lockers along with tire suggestions. Trail ratings and possible requirements needed for specific type of trails. Safety equipment and what you should carry with you. Certified off-road instructor. I am not a mechanic, and 4-Wheeling is a hobby, so if I can't answer a technical question it is due to my mechanical knowledge being related to vehicles that I have owned, or have worked on. I do not have manuals on all vehicles, and I suggest that you obtain a repair manual for mechanical problems and do some research before asking your question. Most mechanical questions can't be answered completely without looking at, or listening to the vehicle in person.

Experience

40 plus years of 4 wheeling in a variety of vehicles. At the present time, my major off-road rig is a 94 Jeep Wrangler with a spring over and a 1 1/2" suspension lift. This gives me a total lift of 7" or so. I have lockers front and rear. I have removed the track bars, and sway bar for maximum articulation. I am running a stock 2.5 ltr 4 cylinder with a Jacobs ignition along with a cold air high flow filter. It has 4.56:1 gears with a Dodge NV4500 transmission along with a 3.8:1 Atlas II transfer case. This gives me a final ratio of 105:1 in low gear/low range. Other vehicles I own, are a 96 Ford F-250 with a 6" lift, posi rear end, 36" Hummer tires, 5 speed with a fuel injected 460 ci engine, an 87 Samurai with an 8" lift, Ford 9" rear end with a spool, Chevy Dana 44 front end with an electric locker, 5.88 gears, 16% reduction in high range and a 6.5:1 low range with 35" Baja Claws, and a stock 2003 Grand Cherokee Overland. Trails I have run are the Rubicon (10 times), Dusey Ershim, Fordyce Creek trail, McGrew trail, several trails in Moab, Utah along with local monthly runs.

Organizations
Lost Coast 4x4's Cal 4-Wheel Corva UFWDA Blue Ribbon Coalition

Education/Credentials
Certified off-road instructor - Certificates in engineering/electronics

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