So this isn't a ticking noise in the engine for sure. 1 out of 3 times, when I start the car, I can hear a very faint ticking noise from the rear. It sounds exactly like a turn signal ticking but except a lot more muffled. What could it be? I checked my lights and their all working.

 

Fuel pump? Turn ignition on, but don't start it. You should be able to hear the fuel pump and compare sounds.

 

Its definitely the Leak Detection Pump; this unit cycles after a cold soak and is used to pressurize the tank to check for leaks. The fuel pump can also be heard for two seconds but is more of a humming sound.

 

So is that bad or good?

 

It is normal and by design. The ECU has built in diagnostics (OBD-II), where the various emissions subsystems will be tested for compliance by the ECU when certain conditions are met.

Some test are continuous, while other occur once per drive cycle if the required conditions are met.

The continuous test are: Comprehensive Component Monitoring; Fuel Trim and Misfire.

The non continuous test are: Oxygen sensor; Evap leak and Catalyst efficiency.

The EVAP leak test will run when the Eugine is cold and the fuel level is between 1/4 and 3/4 tank. This test runs once per drive cycle as does the other non continuous test and the results (pass/fail) are stored in the memory of the ECU.

The results of any non continuous test can be read in $MODE06 with an appropriate scan tool. With this information it is possible to see weather or not a problem exist even before the SES light goes on!

If the test fails (leak is present as in gas cap loose) twice in a row the check engine light will be lit and an appropriate code is stored.

The test are designed to catch any conditions that will cause pollution to exceed the federal standard by 1.5 times. The car has always been doing this but you probably just noticed it.

Hope this help!

 

frenchie, thanks for the info. good stuff to know.

 

I have this code as well. My fuel cap torque click has gotten stiff, and I think it is loosening slightly after I click it tight. Is the fuel cap leak a common problem? It first appeared as a check gas cap light, and turned into the SES light. The code read "very minor vapor leak". Again, I don't have the specific code on hand at the moment. Thanks in advance for any replies, and sorry for hijacking the thread

 

None of my caps have ever leaked, inspect the fuel filler tube and cap for cracks or physical damage.