Check engine light

DONNA PARKS HASH

MEMBER
1997 PONTIAC GRAND AM
6 CYL
2WD
AUTOMATIC
258,000 MILES

My check engine light came on and stayed on. The code said it was the gas cap. We tightened it and he said the light should go off but if not to unhook the neg cable so we did that. The light immediately came back on and stayed on. We replaced the cap with a new one and unhooked the cable again. It came on again. There is a clicking noise when I start the car that sounds like it coming from the right firewall side. Any ideas?

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

There is no such thing as a diagnostic fault code that says a part is bad or needs to be replaced. Fault codes only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. First you need to find out the exact fault code number. I can interpret the definition for you, or you can go here:

https://www.2carpros.com/trouble_codes/obd2

A loose gas cap is the most likely cause of a "small leak detected" or "gross leak detected" fault code, but there are plenty of other possibilities. First we have to look for dry-rotted rubber hoses, loose or rusted hose clamps, leaking valves, and things like that. We start with a visual inspection, then, when necessary, we use a smoke machine to inject smoke under a slight pressure, then watch for where it sneaks out. A lot of leaks would be impossible to find without a smoke machine.