Pausing After Key On Before Cranking

I'm not so sure about these ECU's processing, "millions of things per second". If my 2015 Jeep Grand Cherokee sits for several days to a week without being run, it sometimes will start without the screen booting up. Others on the various Jeep forums have had this issue as well.

This can be remedied by pressing the "START" button twice with my foot off the brake pedal. This allows for all of this electronic crap, (including the screen), to boot up without starting the engine. (The same as turning the key to "ON", waiting, then cranking the engine).

(It also allows the fuel pump to prime the engine). Then, after a few seconds I depress the brake, press it again, and everything starts and boots up normally without issues.
The CPU’s operate on a scale kilohertz (KHz) to megahertz (MHz) to gigahertz (GHz), a thousand times per second, million times per second, and a billion times per second respectively.

The ECU doesn’t have to load a graphic interface, audio codecs, security software, communicate with various other ancillary CANBUS modules, and load up touch screen drivers like the radio has too.
 
I’m not a programmer so I don’t know the exact details and how the terminology started. They’re both a set of programming code, but the different naming was given for a reason.

That would be like saying aluminum wheels are steel wheels. Technically true, because both are alloys. But how would that be useful in a discussion?
I am a programmer and I write firmware/software so I am here to tell you that the lines between firmware and software and pretty blurry. Firmware is definitely software. Windows 10 could be embedded in a device, is it then firmware or software?
 
The CPU’s operate on a scale kilohertz (KHz) to megahertz (MHz) to gigahertz (GHz), a thousand times per second, million times per second, and a billion times per second respectively.

The ECU doesn’t have to load a graphic interface, audio codecs, security software, communicate with various other ancillary CANBUS modules, and load up touch screen drivers like the radio has too.
The ECUs now do a lot more than you think. Most every module in a vehicle is "networked" together so they can communicate.
 
My guess - having not looked into your vehicle specifically - is the screen not booting is a function of the BCU - not the ECU. Why it does that is beyond me - possibly the BCU takes longer to boot or has to get a signal from the ECU over CAN or something else that is firing too soon? If I had to make a guess - I assume this happened later in its life? Maybe the relay that powers it is sticking for a very short period of time and it doesn't get power immediately? Is there a separate relay for it somewhere?

On turning the key several processors typically need to "wake" - ECU, BCU, TCU, usually a separate control module for the air bags, ABS, etc. and there all usually connected via a bus.
Yes it started about a year ago. The car is a 2015. But I don't think it is age that triggered it. I am now retired, and don't drive much. Plus I have 2 other vehicles. (Remember, this is BITOG, if you have less than 7 cars, you're a peon). So it is not uncommon for the vehicle to sit for up to 5 days.

Perhaps, (and I'm guessing here), there is some type of capacitor in the system that holds energy, to fire up the screen. And it is slowly draining over time. This does not occur if the vehicle is driven daily, or every other day, (like it used to).

After sitting for 5 days or more it happens, "sometimes". Then I can do one of two things. Shut the engine down and restart it, after letting it run for a minute or so. Then the screen boots up normally.

Or press the starter button twice without depressing the brake. Then allow it do go through it's whole, "Ding, Ding, Ding" process for several seconds, and the dash lights up like a Christmas Tree, as everything "tests"........ Then go ahead and start normally.
 
Perhaps, (and I'm guessing here), there is some type of capacitor in the system that holds energy, to fire up the screen. And it is slowly draining over time. This does not occur if the vehicle is driven daily, or every other day, (like it used to).

After sitting for 5 days or more it happens, "sometimes". Then I can do one of two things. Shut the engine down and restart it, after letting it run for a minute or so. Then the screen boots up normally.

That kind of sounds like the battery is draining (maybe it has an internal short) and doesn't have quite enough power on the 5th day to crank the engine without a voltage sag. That voltage sag could be causing the problem you're seeing.

Years ago you used to see this with some car radios that would lose the time and presets due to a weak battery when the engine was cranked.

Maybe check the voltage on the battery on the 5th day with a multimeter and see if it's the 12.6V it should be.
 
I am a programmer and I write firmware/software so I am here to tell you that the lines between firmware and software and pretty blurry. Firmware is definitely software. Windows 10 could be embedded in a device, is it then firmware or software?

The what was the mention of 50 computers in a car for without giving more context? Are you trying to make the poor folks here, that always yearn for simple vehicles with crank windows and no electronics, grow white hair or have a heart attack?
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The what was the mention of 50 computers in a car for without giving more context? Are you trying to make the poor folks here, that always yearn for simple vehicles with crank windows and no electronics, grow white hair or have a heart attack?
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What more context do you need or want? They are there and maybe more on some vehicles like it or not! Engine, transmission, ABS, body, HVAC, entertainment, power and heated seats, etc. That has been the case for many years, not just recently
 
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the f150 with direct injection will prime the fuel system when i open the door, i can hear and feel the in tank fuel pump pulsing to prime and bring the system up to pressure.
 
The what was the mention of 50 computers in a car for without giving more context? Are you trying to make the poor folks here, that always yearn for simple vehicles with crank

I don't know if it has 50 computers, but the Chevy Volt is complex enough that it has TWO diagnostic ports. One is the normal OBD-II port that every OBD-II vehicle has, and the other, which is the same connector as an OBD-II port but I don't think it's strictly speaking an OBD-II port, is used for accessing some other modules. The shop manuals for the Chevy volt are 4 volumes which total about 6" thick.
 
That kind of sounds like the battery is draining (maybe it has an internal short) and doesn't have quite enough power on the 5th day to crank the engine without a voltage sag. That voltage sag could be causing the problem you're seeing.

Years ago you used to see this with some car radios that would lose the time and presets due to a weak battery when the engine was cranked.

Maybe check the voltage on the battery on the 5th day with a multimeter and see if it's the 12.6V it should be.
The battery is 6 months old, and is on a battery tender when the vehicle is sitting. It maintains the battery at a state of 100 percent charge.
 
the f150 with direct injection will prime the fuel system when i open the door, i can hear and feel the in tank fuel pump pulsing to prime and bring the system up to pressure.
Mine does that as well, I think it is for the high pressure fuel rail for the direct injection. Happens as soon as you hand goes in the door handle with a key in your pocket and you start to pull
 
The battery is 6 months old, and is on a battery tender when the vehicle is sitting. It maintains the battery at a state of 100 percent charge.

If it were me, I would still verify that the battery is at a decent voltage after sitting for 5 days. Seen enough "it's brand new and works fine" stuff that didn't (work fine) to make me that way.
 
The battery is 6 months old, and is on a battery tender when the vehicle is sitting. It maintains the battery at a state of 100 percent charge.
I don't know that that matters. I believe if a new F-150 isn't started for several weeks it will go into a standy/hibernate mode and turn stuff off. I don't know about your Jeep, but I bet it is something similiar.
 
I tested the battery, and it tests fine. If the starter spun any faster, it would throw a winding.

Doesn't exclude the possibility of some sort of parasitic draw that's draining the battery over a 5 day period even when the battery tender (which is probably limited to 1 amp) is connected.
 
What more context do you need or want? They are there and maybe more on some vehicles like it or not! Engine, transmission, ABS, body, HVAC, entertainment, power and heated seats, etc. That has been the case for many years, not just recently
More context as in only about a handful of these computers control the important stuff, like ECU, TCU, HVAC etc. and the rest are quite inconsequential because they are usually built into the mechanical component, and if the component fails, it is all replaced as one unit.

It just adds to peoples anxiety IMO. This very thread is a good example of that. People worry about stuff that is only in their imagination.
 
The ECUs now do a lot more than you think. Most every module in a vehicle is "networked" together so they can communicate.
Yes but basic running should be dead-nuts reliable. The guys that do the engine computer will give specs to the entertainment system, instrument panel, HVAC etc but will (should) allow the PCM to ignore those inputs if they're wonky or unavailable. Just make sure the anti-theft immobilizer is happy, then maybe throw a code if the rest of the modules don't wake up and communicate within ~30 seconds.

IIRC there's a Mercedes that develops major CANBUS issues if a side-view mirror gets knocked off. Not the car for me.
 
Yes but basic running should be dead-nuts reliable. The guys that do the engine computer will give specs to the entertainment system, instrument panel, HVAC etc but will (should) allow the PCM to ignore those inputs if they're wonky or unavailable. Just make sure the anti-theft immobilizer is happy, then maybe throw a code if the rest of the modules don't wake up and communicate within ~30 seconds.

IIRC there's a Mercedes that develops major CANBUS issues if a side-view mirror gets knocked off. Not the car for me.
Agree. That is where the Check Engine Light comes on when faults are found.
 
More context as in only about a handful of these computers control the important stuff, like ECU, TCU, HVAC etc. and the rest are quite inconsequential because they are usually built into the mechanical component, and if the component fails, it is all replaced as one unit.

It just adds to peoples anxiety IMO. This very thread is a good example of that. People worry about stuff that is only in their imagination.
Sure, but they are still there and doing stuff and communicating so it is reality.. Should I be like the government and tell you none of this happens, don't know what you are talking about.... there are no computers in your car just to curb your anxiety?
 
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