Check Engine Light Due to Gas Cap Issue on Cadillac Eldorado

Problem Description and Possible Solution

A Loose or worn gas cap may cause Check Engine Light to illuminate.

Problem Data
RepairPal Verified
Average mileage: 112,900 (60,000–167,000)
7 model years affected: 1996, 1997, 1998, 1999, more2000, 2001, 2002
12 people reported this problem
Viewing 1 - 4 of 4 comments
On the instrument display I get a " check gas cap". I install a new cap and still have the same display. I did notice a raw gas smell coming from the left rear of car when this happens. I took car to a GM dealer and they tested the vapor problem. They tested the vapor system with a smoke test and a pressure test of the system. Could not find a problem. The system has many parts that can go bad: Fuel limiter vent valve, variable orifice valve, vapor canister vent solenoid, purge valve, fuel tank pressure sensor,. I will have to figure this one out. Maybe one of the parts will completely fail before I find the actual bad part.
I have a light on that says "check gas cap" and the service engine soon light is also on. Don't know why--just started today. I don't drive the car much anymore--only 2 days a week to work on Tuesday and Thursday.
The onboard diagnostic system gave me a check radiator cap notice. I check the cap and it was screwed on firmly. Apparently the cap is getting worn and it intermittently compromises the "Closed system". I have not had to replace the cap yet and the light has not come on in quite awhile. Until it comes on and stays on, I'll keep the old cap.
Engine code is diagnosed as a gas cap problem several previous times. However, the last 2 times this has happen a new gas cap from the dealer was installed. Not sure what to do next to fix the issue!