Now with Video! Intermittent check engine gremlin. Funky Sound.

[papa_wheelie]

Hey all,
I've had an issue with intermittent check engine light. Scan coded with U0121, ABS communication. Light comes and goes. Initially came on after a big rain storm. Now comes and goes. Seems to come on when I'm coming to a stop at a light or something.

I've read it could be dying AUX battery, bad speed sensor, issue with ABS control module, or a CAN issue.

BUT today I realized whenever the check engine light is on, I hear this sound from under the hood. Sounds like something trying to turn on?

Been hearing some very long return times from dealer so I'm trying to diagnose as much as I can myself.

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[Hootbro]

If it more towards the engine front, I would say that is the electric vacuum pump building vacuum for the brake booster.

 

[ShadowsPapa]

I've read it could be dying AUX battery

Careful what you read, weird stuff can be due to low voltage and that can be many things - bad main battery, bad aux battery, or infrequent drives not keeping things up, or some other issue.
People generalize and just toss out "random strange error lights mean......" and yeah, that's one of many things.

If after a big rain storm - did you go through some heavy standing water?
Is it all stock, or lifted? Any chance hitting water gave a wire a yank?

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