1997 bmw

I’ve been having a on going problem with my check engine light… My codes are P0340 and P0455. It’s not my gas cap, that has been replaced 3 times… what do you think?

P0340: Camshaft Position Sensor Circuit Malfunction
P0455: Evaporative Emission Control System Leak Detected (no purge flow or large leak)

For the first code, inspect the wiring to the camshaft position sensor and make sure it’s not broken or frayed (and check that it’s actually connected). If all the wires show good continuity, then there could be a problem with the sensor or even with the PCM itself.

The second code ordinarily would be triggered by a missing or defective gas cap, but since replacing the cap has not worked, there could be a leak/disconnect in the evap lines somewhere.

The second could also be a failed purge solenoid/valve.

could it possibly be the catilytic converter?

There are hoses and lines which connect between the gas tank, the charcoal canister, the purge control valve. The rubber of these hoses can deteriorate over a period of 11 years and allow the EVAP. system to leak. The allowed leak is very tiny.
Your repairer could examine these hoses and replace any which have cracks or other deterioration.
The car dealer has a very expensive smoke machine with which to test for evaporative leaks. A test for you would help to defray the cost of that machine. So, try the less expensive diagnostic techniques first.

What model? If you can tell me this I may be able to help with common failures.

Not with these codes.

I have a 1997 bmw 318i. i’ve already had the gas cap replaced and the Cam sensor was replaced still my check engine light remains on…

Same codes?

couldnt say if the codes were the same before, but i’m thinking yes. because maybe thats why they replaced the cam sensor.

Replacing the cam sensor may have taken care of the code P0340; but, it would have NO effect on the code P0455. The only way to know, is to get the codes read with a scan tool (code reader). Some of the larger auto parts stores will scan the codes for you, free. Just ask, and bring any codes reported here for advice.

You may need to change repairers. Some repairer who changes the gas cap three times is missing something (like using the wrong troubleshooting techniques).

you are guessing, since you have not had the code read again. you may have solved the problem, or you may not have. but unless you read the codes you wont know.

you have to re read the codes each time you repair ONE problem. how else would you know if you actually solved anything. this would be different if you only had ONE code, but you had two. at this point you are not even sure which code (or two) is there. or which thing you replaced even worked!

if you had the codes read, then drove home to fix it, you still have to read the codes, and erase them, to see if they come back. if you wait it takes around 10 or so drive cycles to turn off the code. then the two code problem comes up, which one shuts off?

about the gas cap. has this car had any body work done recently? any under car repairs lately? it is possible someone didn’t tighten one of the hoses on the gas fill lines, or knocked one loose, or (with the age of the car) one of the hoses may be cracked or leaking.

the comment that three gas caps indicates you need to find another mechanic is true too.

let me clarify, after the repair of replacing the cam sensor and the gas cap these two codes, p0340 and P0455 are still coming up. My question was , what can i get the mechanics to check to fix these codes.? and thank you

We have already told you: Get a more capable mechanic and check those areas that we have already mentioned. Why are you ignoring these ideas?

don’t take it personally, HelloKitty, I will take all of the answers into consideration. Thank you to all…