Jim Grant's Tech Tips
Civic, Gas Cap or Problems?
Q:# I have a ‘96 Honda Civic CX. The engine light
came on. Honda service read the computer code, reset the engine light
for $34. They told us it might be a defective gas cap or improperly sealed
cap and advised us to make sure it is sealing properly by turning it until
we hear the clicks. Within a week, the engine light came on again. Honda
service read the code, same code as before. Reset the engine light for
another $34. They changed the gas cap for a new one just to make sure.
$13 + tax. The engine light has just come on again. #1: Is there a way
to check if the gas cap was/is defective in the first place? When we remove
the cap, we hear a distinctive whoosh of built up pressure. Should this
not confirm that there is no leak around the gasket or anywhere else?
#2: Is there a way to check the pressure transducer? If so why did they
jerk me around thinking it might be the cap? #3: Why is it important to
measure this gas pressure information? Can I ignore this error condition?
#4: Can I check these codes and reset the computer myself? Someone said
I could do it with a simple module. I might even be able to see this information
via a serial port using a computer/laptop and diagnostic software. I would
appreciate any help you may give me in this matter.
4. Yes you can check your vehicle’s computer for Diagnostic Trouble Codes
(DTC’s) and reset the computer yourself with a lap top computer. Search
the internet with key word (OBD II). This will take you to many sites
that sell such equipment.
Yes it is important to monitor gas pressure. Why? If a vehicle’s gas tank
is not sealed properly, the volume of raw Hydrocarbons HCs that escape
into the atmosphere exceeds what comes out the tail pipe of your vehicle
many times. Yes, today’s vehicles are that clean out the tail pipe. By
monitoring the pressure in the gas tank the vehicle’s on-board computer
can identify an evaporative system failure. The evaporative system is
more than a gas tank and cap. It also incorporates a charcoal canister,
hoses and tubing that travel the full length of the vehicle, computer
controlled/monitored solenoids and pressure sensors.
#1 & 2 As for the jerk around, all I can say is when one of our customers
come in with a light on and no driveabilty complaint we ask if the vehicle
has been fueled up recently. Why? Because the gas cap may not be tight
enough. This has happened a lot and we’re just a small town garage. We
check and demonstrate proper gas cap installation and close with the recommendation
that the vehicle be driven for a few days at no charge for our time educating
the customer. The alternative is plugging in and charging you for the
computer scan tool, plus labor time to go through a factory diagnostic
procedure, monitor the pressure sensor etc. (takes more time than you
can image) to tell you that the gas cap was loose. Many areas have or
are in the process of implementing (including New Hampshire) emissions
testing that requires checking the computer on ‘96 and newer vehicles..
This is only the tip of the iceberg, there is so much more to explain.
As a consumer you have so much more to learn. I’m sure there will be more
discussion in this area.