Lately we have had in the shop customers with a DTC (Diagnostic Trouble Code) that is not always the DTC directly caused by a bad gas cap but effect other ECU monitored areas of engine operation that will activating several DTCs.
Most any Dealership service department or independent service shop will charge a Diagnostic fee to first find any and all DTC. Then it becomes a systematic elimination to either test or by experience rule out some of the causes of the DTC's. The most common trouble codes but not all associated with a faulty gas cap are P0440, P0455, and P0457.
In most shops I mentioned the diagnostic fee is not part of the solution so you will be charge generally either a 1-hour diagnostic fee or however each service departments charge for a diagnostic fee. So for some that will amount to a estimated service charge ranging from 75-150 dollars or more to get a service final report showing all the possible causes of the DTS(S) At which you will an estimate charge based on what DTC were found the possible charges to correct the problem that caused the DTC. There is NO set order of elimination because there are factors not included in the basic Diagnostic service guides like millage and visual basic conditions of the area that is to be serviced. So while many will find a list of DTC explanation on the internet for the most common 'fixes" they are still a guess. The most common is replacing the gas gap. This will work some of the time, but we also have customers state that they replaced the gas cap, and the DTC still return shortly after. So, the cycle returns to the begging of this post.
What are service records showing the number of gas caps replaced in a year is about 30+. And a couple or more are returning in less than 2 years to get another gas cap replaced. The biggest reason gas caps fail is none service to them. There is no service recommendation that I am aware of that show a HOW-TO or advise to service the gas cap and gas cap area since we at our shop started to do a simple service for our customers the number of returned gas cap replacements has lowered. I will state that there is not test control based on the simple easy to do service if it did directly affect the numbers but looking again at our records since last year any customer, we replaced a gas cap and service the area has not mentioned, and we ask having replaced their gas cap since our service. I should also mention that we DO NOT charge for the cleaning of the gas cap area, and it is included when we do a service that is affected by the gas cap area.
The simple and logical sense is that when you get gas you remove the gas cap and set it aside either on the gas cap door or on the gas pump. This means you expose the filler next to the environment. The wind, rain snow etc can and does get on the filler next when you get gas. The gas pump nozzle is also 24/7 exposed to the environment. The gas pump nozzles are only service every 3-6 months so there is a lot of dirt and other debris that build up on them in between the serving. That debris on the gas nozzle can and does get not only in the entrance of the filler neck but also into your fuel tank.

For the gas pump nozzle, it easy enough to take a paper towel generally available at the pump and wipe the spout that goes into your fuel next for filling. Common sense if there is a lot of accumulated grime or just overly dirty go to another pump.

For the gas cap and filler neck area it is a simple 10 minute and easy to-do for any owner of a vehcle regardless of DIY or mechanical aptitude and experience.
Remove gas cap
wipe the inside area of filler neck
remove if applicable the oil ring on the gas cap
Useing a new clean rag wipe the inside area of the gas cap. You may need a little WD-40 to help with really dirty areas
Wipe and or replace the O-ring if the oil ring appears to have cracks or will not hold a round shape.
Reinstall oil ring
reinstall gas cap.
Wipe the inside area of the filler neck, gas cap area only after the gas cap has been reinstalled

DONE!

SIMPLE


This is only a suggestion but based on my experience you may want to buy and have one handy and replace it as a 50-80K mile service. Gas caps are inexpensive and at some point, the averages show you will need to replace it at some point. I will also add that if you check with your state the number one cause of emission testing failing is due to a faulty gas cap.


Basic pictures servicing pictures. Many areas will vary slightly depending on the year and model platform.

 

Since the beginning of the new year, we have replaced for customers 36 gas caps.
Reason:
Number one reason...Failed (all reasons below) and caused DTCs

Gas fumes from a bad seal

Dirty gas cap and gas cap encloser area This can cause excessive dirt and debris to get into the fuel tank and clog the filter or cause the fuel pump and other fueling system problems.

Missing or lost

Take the time at your next fueling to look at the condition of your gas cap. They are very inexpensive and anyone can replace them. As well even a glove box hand wipe can clean the gas cap area or use a supplied windshield paper towel often available at gas stations..

 

Bumping thread up. Last week we replaced or serviced the gas cap area as problematic on 6 customers vehicles.Most is a dirty gas cap area or faulty seal on the gas cap because of age