Noisy at Idle

[YarisHybrid2016]

Hi,

I noticed recently when the car started cold due to low HV Battery, it sounded very noisy.

Best description is it sounded like the exhaust was loose and rattling in its mountings against the body.

I stood outside and it sounded normal. I increased RPM slightly (I found how to do this in PARK), and returned it to idle. The loud noise did disappear, then returned.

I'm confident it is a rattle (more like dull thudding) from the exhaust system somewhere, but at a loss where to look.

It doesn't always occur, only seems present at "charging idle", and disappears when the engine accelerates, or reduces to low idle before shutdown.

It doesn't seem to be present when driving.

Is there anything I should be looking for? With it getting on for 3 years old I did wonder if the exhaust was corroding, but when I looked at it, it appeared OK.

I'm wondering if a bracket is loose and resonating at idle. It's really quite loud in the cabin, like it's thumping the floor.

Thanks in advance.

[Mike J.]

This maybe a generic Toyota hybrid problem, check out this:

Prius knocking noise

which mentions "MIL "ON" DTC P030# After Cold Soak" and a web search on this gives:

Lexus CT200 knocking noise

This webpage seems interesting and may be valid for our cars:

Cold soak rattle