[ChevyGuy]

I think this should be moved to Gen1.

Typically hyperflashing is because a bulb is burned out. You might verify that all the lights are working.

It's possible that you might have hyperflashing if the system is overloaded (too many lights). You might check your trailer system to see if is has resistors. If it does, I'd remove them.

 

[ChevyGuy]

You say the trailer has LEDs so yes you do need load resistors for them.

I disagree. The trailer is in addition to the lights in the car. Since the hyper flash only happened when the trailer was attached, I have to think the trailer was overloading since it's impossible for a added load to "under load".

 

[ChevyGuy]

I had this problem with my son's car and it turned out to be the "multi-function switch". Does it stop doing it when you turn on the turn signal hit the turn signal stalk or turn on the hazard lights? Since cars don't have individual turn signal flashers in the fuse block anymore, somehow the trailer/ LED lights may have blown out the flasher assembly in the multi-function switch. this switch is the combination turn signal/wiper assembly switch on the on the steering column.

Valid for "conventional" cars, but I don't think it applies to the Cruze. The Cruze has no flashers. That's all done by the BCM. The controls tell the BCM what you want to do.

OP, does the hyperflash happen for both left and right or just one direction? If just one direction, recheck the turn signal with as many lights on as you can. See if it works normally and has normal brightness. I'm thinking you might have a bad ground (perhaps caused by modifying the wiring for the trailer), or you have a old bulb that isn't drawing as much current as it should and confusing the BCM.

The last idea is that the trailer has somehow damaged the BCM ($$). But before that, I'd try disconnecting the battery for a few minutes to try and reset it.

 

[ChevyGuy]

Check the flasher relay, u may not have individual fuses anymore but even the 2017 Cruze has a flasher relay. Mine was under the dash right below the steering column on the left side.

I don't know about the 2017, but my memory of the 2013 schematic shows all the bulbs are driven directly by the BCM. The stalk just feeds commands to it. The clicking noise is created by the radio on commands found on the car's data bus. One way this becomes obvious is when using the 4-way flasher. With the car running, turn on the hazards. Now, turn off the car and open the door, killing the radio. What happens to the click? On my car, it disappears.

A 2005 is probably closer to a 1970's car in the way the lights are wired. If it's the kind of car where the brake lights do double-duty as a turn signal, then the stalk has to disconnect the brake line on that side to change the brake light to a turn signal. Lots of switch contacts. If that switch fails to connect, the lights don't work right and you can get hyperflashing.

I hate to say but the BCM was likely overloaded and damaged,

That's my fear as well. But might as well try the cheap things first. I do seem to remember having a old bulb that didn't draw the right current and causing flashing problems. Bulbs are cheap, so it's worth a shot.