Isn't the ICU up by the master cylinder? OPs picture sure looks like the vacuum pump to me. This is the service manual's photo:It's called the Integrated Control Unit (ICU). It is used to store extra fluid released from the calipers during ABS mode operation. It uses a DC operated pump to clear the brake accumulator of brake fluid for proper ABS function. It also includes valves to modulate brake pressure during anti-lock braking, Brake Traction Control, and Electronic Stability on each wheel individually without any driver brake input.
If you go to Brakes, ABS, Description, in the DT service manual the green highlighted item 1 is in the approximate location of the front, left side of the engine. The text in the description does say it's located near the master cylinder. My copy of the service manual is missing all four figures which might explain some confusion, but I don't see a reference to a "vacuum pump."Isn't the ICU up by the master cylinder? OPs picture sure looks like the vacuum pump to me. This is the service manual's photo:
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That's the oil dipstick handle (yellow) at the very top of the factory picture.
I agree. I see it and in the diagram you noted the device under question appears to be graphically represented. I was not looking at the Brakes Base, obviously. Now I'm not sure why they split the brake components up into two separate sections.Under Brakes, Base, Description, Description and Operation - component #7 is the Electric Vacuum Pump. Under Operation, it says, "The base brake system uses an electric vacuum pump for additional vacuum supply".
The hiss only lasts maybe 1-2 seconds at most and comes from the vacuum pump and not the brake booster (climbed in the engine bay while my gf hit the brakes). I must have never noticed it in the last three years of owning the truck.When you release the brake pedal, the vacuum in the booster is dumped into the atmosphere, so you may hear a hiss or whoosh. If the hiss continues when you are not doing anything, you may have a leak.