We’ll remove the gas cap and look for damage to the gas cap, o-ring, and filler neck. We will often wiggle wires and hoses while looking, listening, and even sniffing for changes. The Five SensesĪ technician will look for loose, missing, or damaged components. Understanding a system and how it works is the essential first step towards identifying a problem with a system when it doesn’t work according to design. Knowledge About The System Being DiagnosedĮVAP control strategies vary from manufacturer, model, and model year. When I asked my wife, she said that she received the recall letter, but didn’t think that it was important because the “car drove fine”. A few minutes of research saved me from a few weeks of pulling my hair out trying to find the problem. It didn’t take me long to find out that Toyota had issued a recall, and her Corolla was one of the affected vehicles.Īn ECM manufacturing flaw was causing false EVAP codes to set. There was an issue with my wife’s 2005 Toyota Corolla that caused several false EVAP diagnostic codes to set.īefore doing anything else, I checked for recalls and technical service bulletins. Are there any known issues with the vehicle that could explain the presence of the diagnostic trouble code. The technician diagnosing your vehicle should also look for EVAP related T echnical Service Bull etins (TSBs). It got a little chewed up, but my brother said it would be fine”.Ī little information goes a long way towards finding the solution to a problem. We had a lot of trouble with one of the seals. “Oh yeah, me and my brother had to drop the gas tank and replace the fuel pump. “Have you had any work done on the car?”. You should be asked questions about your vehicle.
The Basicsīefore reaching for high tech solutions, a technician should review the basics. That’s why its important for you to have your vehicle diagnosed at a shop that employs technicians with the skills, training, and equipment necessary to correctly diagnose and repair your vehicle without wasting your time and money on unnecessary repairs and hopeful guesses. There’s more to look out for than bad gas caps. Some vehicles have had issues with spiders laying eggs in EVAP vent lines while others have problems as simple as corrosion preventing a good seal between the fuel cap and fuel filler neck. Some faults are caused by leaks while others can result from blocked lines, faulty sensors, or malfunctioning solenoids. Always follow a vehicle manufacturer’s procedures when performing tests or repairs of any kind.ĮVAP related diagnostic trouble codes that turn on your check engine light can be set for a variety of reasons.
It is not intended to be exhaustive, complete, or even applicable to all situations. The information presented below is an example of diagnostic strategies that a technician might employ while diagnosing your vehicle’s EVAP system. Loose and missing gas caps are not the only cause of EVAP system leaks, but they are the number one suspect.
#Toyota diagnostic code p0442 series#
Under specific conditions, often while your vehicle is parked overnight, your vehicle’s on board diagnostic system (OBDII) will perform a series of EVAP system tests.ĭuring EVAP testing, a loose or missing gas cap will be detected as a leak, a diagnostic trouble code will be stored, and the MIL will illuminate.Ī loose gas cap might result in a P0442 code, (Small leak detected), and a missing cap could return a P0455 (Large leak detected). When many people see a “Check Engine Light” (Proper name: Malfunction Indicator Light a.k.a MIL) they immediately think, “Check the gas cap”. That’s because a missing, loose, or damaged gas cap often is the cause of an illuminated MIL due to a failed EVAP leak test. These fuel vapors are added to the engine’s air fuel mixture and are burned off as part of the normal combustion process. When your engine is running and warmed up, engine vacuum siphons stored fuel vapors from the EVAP canister and into the intake manifold. How Does The EVAP System Work?Īs stored fuel in you r gas tank evaporates fuel vapors are collected and stored in a canister filled with activated charcoal ( the EVAP canister). That’s why hydrocarbon control and reduction is a major component of your car’s emissions control strategy. These compounds are also known to cause eye irritations and respiratory problems. Photo chemical smog is that brown hazy stuff that nobody wants to see in the sky. Why?įuel vapors are composed of hydrocarbon molecules (HC) which when exposed to sunlight and oxides of nitrogen (NOx) result in photo-chemical smog. The evaporative emissions control system (EVAP) on your vehicle is designed to prevent fuel vapors from escaping into the atmosphere from your gasoline tank. Evaporative Emissions Control System (EVAP) What Does The EVAP System Do?
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