Check engine message

[marilyn_monaro]

I'm aware there's lots of threads about it but can't find anything similar to what I have. I get the check engine message a few minutes after every start up, I can cancel it and it won't show again for the rest of the journey, until the car is started again. This happens whether hot or cold.

I changed both 02 sensors as it used to give me the dreaded beep lots of times but after that it settled on just once. I also changed the oil pressure sensor, a genuine one, no difference. Tried to check the code in the dash and its all zeros. Tried my code reader, still nothing.

It doesn't affect how the car drives, no lumpy idle or anything, it's more of an annoyance. Im leaning towards maf or pcv valve. Has anyone had a similar occurrance?

[SturdyHSV]

I think the random check engine messages like you're seeing that don't effect drivability in any way are likely to be emissions related, so yep, something along the lines of O2 sensors.

You say changed both, I think there are 4 aren't there? Certainly on the LS2 engined Monaros anyway, 2 pre-cat and 2 post-cat.

If anyone local to you has EFI Live that will read the codes off

[Lincsls1]

There are only 2 sensors on the 04 cars, 4 sensors on the facelift 5.7 and LS2.
Given that the issue has much improved since they were changed, it might be worth changing them again. I once fitted 2 new sensors to my old 300zx and one of them was 'lazy' out of the box.
What is the exhaust setup like? Are you running original CATS?

[marilyn_monaro]

Thanks for the replies. Yes I have an 04 so only 2 sensors. They were both genuine/ac delco, I can't recall which. All I know is they were a pig to get out lol.

Standard setup and original headers. Exhaust has been changed for stainless from cat back.

[vxr2010]

Getting the correct working sensor can be an issue , i bought a few from rock auto that did not work very well or last very long and did not change things , the sensors also don’t last a long time v other cars , i expect our cars running quite rich causes issues , make sure your battery is in good state as is it getting discharged and then Charing when you are driving and your issue going away , if you look at the FAQ section the last post on it , i did a write up on sensors which may help , where are you based I’m herts so should be able to code read

[marilyn_monaro]

I replaced the sensors around 6 months ago, and actually put a new battery on 2 weeks ago, but no change still get the message.

I'm in the West Midlands

[vxr2010]

Possibly a dirty air filter , mine got quite bad after not a lot of miles , next option is code read , sometimes the 02 sensors throw up a cel when nothing is wrong any way , an intake air leak , made worse on start up ? My intake pipe had a crank under it , cel for 02 came up , new pipe it’s been fine since