2004 Tahoe/Tahoe Random Chirp Under Dash While Driving

[Roilux]

I'm going to shoot off on a tangent. In another thread that I can not currently locate, the OP was working on a fuel delivery issue. He mentioned an unfamiliar sound that I also heard in my '04 LT 5.3 Flex the day prior to reading his thread. Chirp like? Kind of. It happened again the following day but only when driving. Then the following day - lots of 'chirps' while driving and then a no-start condition. Measuring fuel line pressure displayed a fluctuation around 42psi.

A new fuel pump went in, engine starts quicker than before and no more chirps. Is it related? Possibly. However, I've no clue what in the entire fuel system would make such a noise.

 

[mitman64]

Interesting point. I do have a nuisance P0455 code due to a crack in the plastic at the fuel sending unit. Obviously, that’s on the top side of the gas tank and I’ve been too lazy to drop the tank to replace it.

I was wondering if there’s some kind of “bit bucket” that fills each time the system checks the fuel pressure for a leak. When the bit bucket fills the check engine light illuminates and the error code is active. Maybe, each error bit causes the “chirp”. But, all of this is just guessing. And, where is the “chirp” speaker?

 

[Fless]

Interesting point. I do have a nuisance P0455 code due to a crack in the plastic at the fuel sending unit. Obviously, that’s on the top side of the gas tank and I’ve been too lazy to drop the tank to replace it.

I was wondering if there’s some kind of “bit bucket” that fills each time the system checks the fuel pressure for a leak. When the bit bucket fills the check engine light illuminates and the error code is active. Maybe, each error bit causes the “chirp”. But, all of this is just guessing. And, where is the “chirp” speaker?

I don't believe there is any fuel pressure monitoring in the GMT800 series, so I doubt there's any checking being done for that.

 

[mitman64]

The data must be tracked in some way as I can see the error pending when I scan the ODBII. If I don’t clear the pending, at some point it changes to active and the check engine light illuminates. Maybe the better question is, is there a piezo buzzer or speaker associated with any circuits? I sure haven’t found one.

 

[Fless]

The data must be tracked in some way as I can see the error pending when I scan the ODBII. If I don’t clear the pending, at some point it changes to active and the check engine light illuminates. Maybe the better question is, is there a piezo buzzer or speaker associated with any circuits? I sure haven’t found one.

Don't confuse fuel pressure with fuel tank pressure. Those are two different things.

You are correct that on the second failed evap test (which is essentially a vacuum test of the closed evap system), the evap code sets as an active code and lights the MIL. But unless something's been added to the vehicle, there's no buzzer/speaker involved with the evap system. Just the MIL.

 

[mitman64]

Thanks for confirming that. At least I can stop looking in that direction.

 

[S33k3r]

The data must be tracked in some way as I can see the error pending when I scan the ODBII. If I don’t clear the pending, at some point it changes to active and the check engine light illuminates. Maybe the better question is, is there a piezo buzzer or speaker associated with any circuits? I sure haven’t found one.

The only one with which I am familiar is the one associated with the OnStar system. I say "familiar" because I hear it coming out of the driver's side kick panel of my Escalade ESV or the driver's side door only. And very, very low.