Cadillac Owners Forum banner
1 - 2 of 2 Posts

·
Registered
1999 Cadillac Deville
Joined
·
23 Posts
Discussion Starter · #1 ·
My 99 kept throwing gas cap codes. So i replaced it three times. It finally dawned on me that the cap was not sealing properly. It was not the caps problem, it was the dirt and some debris that had built up on the filler neck.
So I removed the cap and stuffed a new clean rag in the filler neck and gently cleaned the seat where the cap was hitting on.
I took a vacuum and vacuumed the debris out of the rag while I removed the rag so that no debris coulb get into the filler neck.
Reseated the cap and the codes have not returned.
Happy Hunting
 

·
Administrator
2002 F55 STS, 2014 Explorer XLT, F-150s
Joined
·
75,902 Posts
When the code returns keep in mind that the "gas cap" code and message is set by an EVAP system pressure/vacuum problem, usually sensed by the fuel tank pressure sensor. Many times that code is tripped by one or more of the rubber lines to/from the EVAP charcoal canister - and/or by a faulty gas cap/seal.

Here's a generic diagram of a 1998- 2004 EVAP system. Check the green cap on the system test port (10) - near the power brake booster.

Text Diagram Parallel Line art
Automotive fuel system Auto part Fuel pump
 
1 - 2 of 2 Posts
Top