How long does it take for radiator fans to cycle on in maintenance mode?

Hello all,

I'm new to Prius chat and Prii in general. Here's my story:

I'm in the process of diagnosing a P0401 code and somewhere along the line I got sidetracked by a low ICE coolant reservoir level. It was practically empty. I topped off the level to the full line and switched the car into maintenance mode to circulate the coolant. Then I waited for the cooling fans to cycle on. I waited a solid 20 minutes or so. The night air was somewhere around 60 degrees give or take. They never came on.

Now, I've overheated a Volkswagen Jetta in my time so I was reluctant to continue the experiment for fear I would succeed in doing the same to the Prius so I shut it off. Again, I'm a novice to this type of technology but I'm assuming the A/C and heater don't require the use of the radiator fans to function because they work just fine. I've owned the car since July and honestly, I want to say I vaguely remember hearing the fans come on, but I'm more inclined to believe I've never heard them on. Is this normal operation? I started reading a thread concerning different warm up stages but this was too hyper-technical for me. I'm not looking for a concrete answer because I figure there are too many variables to consider. I drive the car over hundreds of miles a day several times a week doing food delivery for DoorDash and have never had a warning light come on excluding that check engine light associated with the above mentioned code.

With regards to this code I've removed the EGR valve and cooler, cleaned them, along with the pipe that attaches the EGR valve to the intake manifold. The pipe is where the majority of the carbon deposits were. Although I believe the EGR cooler could have had more, you just couldn't see it with the fins and all. I crudely looked over the EGR valve depressing the threaded part in, after removing the magnet, stalling the car so I deemed it as working but who knows? The operation of the valve is beyond me really. I understand it's solenoid operated and it's got a spring inside the magnet. That's all I know. Speaking of the manifold, I just recently removed and cleaned it and the throttle body, replacing the manifold gasket but the light remains unphased, taunting me and my DIY efforts.

I will say however, that after removing the EGR pipe the second time around I did notice it was wet on the inside. I chalked it up to the fact that I was running non-ethanol gas at the time, but I've since read online that this could mean the cooler is shot and leaking coolant. An exhaust leak basically. In fact, now there is an audible noise from the front of the vehicle when the ICE is on that gets louder with acceleration. Almost like a hollow rattling sound. Truthfully, it may be the reason why the coolant was low to begin with. I'll monitor the level in upcoming trips.

Now, I'm looking into the DPFE sensor or vacuum leaks around hoses. Maybe replacing gaskets around the cooler. I'm sure they've seen better days. Also, I did notice a hose attached to the VSV has cracks at the opening. When it comes down to it, it could just be a blockage in the EGR cooler that's triggering the sensor. I don't know. It seems like a good idea to replace it anyway but I'll take any other suggestions. I'm looking for a relatively cheap solution before throwing hundreds of dollars in parts into the car only to have the light return.

The car runs like a dream yielding an average 50-55 mpg consistently under a myriad of weather, terrain, and driver input conditions so perhaps I'm just overthinking it, but I'd rather air on the side of caution. Any input will be greatly appreciated. Thanks.

 

Thanks for the advice Chap. I'l invest in a decent scanner tool and go from there. I did have the heater temperature set to 80 F with the blower on the highest speed. I thought it would speed the process up. Looks like I was mistaken.

 

174500. The fans did work after all. While driving I stopped for a moment to check my blinkers when what do you know I hear the sound of fans. Sure enough, they were cycling on and off. I'm so used to hearing them in my Civic, that I thought the same sound could be heard in the Prius' cabin. I was mistaken.

 

No, not in maintenance mode. ECO Mode. I had been driving for a good while as well.