Hi there,

I'm trying to help a friend out with his 2016 ES... The short summary of the problem is only when the car is cold (ie, first thing in the morning, or after sitting for at least an hour or two) the car will not attempt to start. No turnover, no crank, no click. But the radiator fans will instantly kick on and run for about 1-2 minutes (engine temp in the dash also correctly shows the engine is cold). After the fans stop, turning the key instantly starts the car. So it's like the car thinks it's too hot/overheating and withholds any starting attempt. After letting the fans run for a couple minutes, it is then content to allow the car to start no problem. Yet when the car is already warm (ie, after driving and stop to get something at the convenience store), it will restart without issue (engine temp in the dash also correctly shows the engine is warm).
A couple observations I have already addressed:

• I have replaced the actual thermostat with one that I have temperature tested outside in a pot of water so I know it works as it should
• I have resistance-checked the coolant sensor at the thermostat housing at all ranges of temperatures and it responds as expected so I assume the sensor itself is fine
• I have read the car for codes and got the following plethora of errors:
  • P0123
  • P0222
  • P0118
  • P0113
  • U0100
  • B210A
  • C1290
  • U1417
  • C121C
  • C1561

I am certain most of the error codes are simply auxiliary to what the actual problem is, but does anyone have any thought of how to address? It's like some sort of cooling/electrical issue that is boggling me.

 

What other things do not work when the car will not crank

 

I believe pretty much everything works otherwise...without being able to start, are you wondering about anything electrical, like lights and such? Radio, exterior/interior lights all function fine. When the car won't crank, the dash does show:

1. "Check" Coolant
2. ASC "Service Required", and
3. A large "Check" Triangle/Exclamation Point

...again, I think the ASC and generic "Check" icon are auxiliary, and not actually real, compared to why it somehow believes there is coolant issue (when the fluid level is fine and the engine is cold).

Is there anything specific you think I should double-check to see if still works/doesn't when the car won't crank?

 

If your rad fan is running (when it should not, but you key on) it likely is a "default strategy" to turn them on because the PCM is detecting something wrong. It may be sensing a shorted or open reference to your sensors (they likely all share a 5 volt reference)

Here is what I would do.

During the 'fan running' event- check one of your other sensors to see if it has a valid 5 volt reference, ground and signal. If it were me, I would chose something simple to access, like the throttle position sensor. In my scenario it would be easiest to hook my o-scope to all 3 leads at the same time since I use a 4 channel scope.

If your reference is lower than 5 volts you could have an intermittently shorted sensor which is pulling down the voltage to everything. This would very clearly explain why your car will not start.

Think of measuring the 5 volt reference like going to the doctor, and the first thing they do is take your pulse. If you had no pulse- then there is no good reason to continue trying to diagnose further, right?

 

My apologies about the delayed reply -life just got a little hectic for a bit- but I appreciate the suggestion.
I also came across a Safety Recall Bulletin that seemed to fit my issue and lo-and-behold after replacing EC and rad fan relays, the car seems to operating normally again! What a nightmare-ish simple issue...will let my friend deal with why the dealer never looked into that in the first place.

Thanks again for listening and throwing your ideas my way.