Popping sound from speakers when turning key

[dwonder]

Hey again everyone,

When I bought the car, previous owner told me about the popping sound and as days go by it’s starting to bug me more and more. Whenever I turn the key (whether I start the car or just turn electronics on), the popping sound occurs once. It sounds like it’s coming from the rear speaker (similar to someone hitting the trunk with a hammer lightly). I saw a thread on e46fanatics about it but there wasn’t too much detail there.
Anyone have this issue on where should I start first? I’m thinking the ground wiring for amp but not sure where that is located.

Thanks in advance for your help.

[ZHPizza]

Check the battery health first. That's one of the many wacky symptoms that these cars get when the battery ages.

[dwonder]

Good idea! Looks like battery hasn’t been replaced since 2007 / 50k miles ago.

Edit - battery is actually relatively new.

[dwonder]

Just brought the battery to AutoZone to get tested. They said it looks normal (battery manufactured February 2018). I plugged battery back in and car barely started, had rough idle for first few mins then check engine light popped on.
What should I do?

[ZHPizza]

Just brought the battery to AutoZone to get tested. They said it looks normal (battery manufactured February 2018). I plugged battery back in and car barely started, had rough idle for first few mins then check engine light popped on.
What should I do?

Did you have them scan the CEL code?

[dwonder]

I took battery out and brought to autozone. Didn’t drive the car there; I’ll do that another day so they can check alternator and SES light. I hope it’s just cause the voltage is low since the guy told me it was showing 70% when he checked.

[ZHPizza]

That's probably it. The battery test puts a good bit of strain on it. Fyi the $15 bluetooth OBDII readers on Amazon are surprisingly functional for pulling basic fault codes and tracking stuff with the Torque app.

[dwonder]

My indy pulled the codes. He says nothing to be concerned about and battery looks fine also. I called the dealer and they sell the OEM batteey for $205. I might do that next time I need one. Both Indy and dealer says that no registration or coding is required for the 2003 330i when putting in any new battery, whether it is the same or different. Is this true?

[ZHPizza]

Yep no coding needed on the e46 and no reason to pay for the dealer battery

[dwonder]

Thank you sir! Since battery is okay, where should I look next to find this popping sound? I’ll likely just live with it for now if I can’t find out what’s causing it and it isn’t causing an issue elsewhere.