Smart Key Functions Not Working

welcome!

i have no idea, but a wild guess would be a faulty pc board that heat is somehow correcting/connecting

 

Your 12V battery is actually a lot lower; probably closer to 11-11.2V. No wonder the SKS isn't working reliably.

Using the vehicle signal check provides a very inaccurate SOC (State of Charge). Do yourself a favor and get a DVM (Digital Volt Meter) and check the 12V battery health this way.

1) Let car sit overnight.
2) Foot off break, press Start twice: IG-ON mode.
3) Headlights on HIGH
4) Vent fan on high, AC off
5) Radio on, low volume.
What reading do you get? Measure at the 12V battery terminal posts or the jumper posts in the engine compartment.

Recharge the 12V AGM battery w/ a "smart" battery charger that has an AGM setting. A regular 12V battery charger will not fully recharge a 12V AGM battery.

14+V is a normal reading when the car is READY. The vehicle's 12V bus is recharging the 12V AGM battery. This is equivalent to a conventional gas car with the engine running, and the alternator spinning supplying 13V to the 12V battery to recharge.

Reference the SOC (State of Charge).

Another person has a different approach to load testing the Prius 12V AGM battery; I prefer my way b/c of a greater load:
1) With car off measure battery voltage at the front jump point. Write that down.
2) Then with car off, turn on headlights in high beam and leave them on for 5 minutes.
With headlights on at the end of 5 minutes measure the voltage.
3)Then turn headlights off and with car still off measure battery voltage. What are the 3 readings?

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As for elevated ambient temperature making the SKS work correctly. It could be an intermittent circuit that is "open" when cold, but "closed" when hot. But, I speculate that the increase in ambient temperature is elevating the 12V SOC, allowing the SKS to work.

Did you rewire this outlet so it is always HOT (meaning always on)? If so, this will be draining your 12V battery unnecessarily, esp since you have the dash cam plugged into it.

 

I would recharge the battery first, to rule it out as the source of the problem. If a fully recharged 12V battery does not make the SKS problems go away, then you know it is NOT the 12V battery. Be sure to recharge w/ a battery charger that has an AGM setting, as a regular battery charger will never fully recharge an AGM battery. If you don't have a AGM compatible battery charger, you could just leave the Prius in READY mode for 12+hours (the longer the better; maybe a full 24hrs), to slowly recharge.

11.6V is LOW. It is 3/4 depleted, OR, 1/4 fully powered. RECHARGE ME ASAP.

 

Most likely the problem will disappear when you get your 12 V battery problem sorted out.
BUT.....the symptoms also sound much like a failing lock actuator solenoid.....which is fairly common.

 

Chaosphere, I can't offer information on the smart key module. However, we are having the same problem as you. Will you please post here to let us know if the 12v battery charging fixed the problem for you?

 

Hey Chaosphere, so, mine is the opposite temperature of yours. When I start it every few hours the remote works fine each time, although the range is terrible always, you have to be standing 15 feet or less for it to work. However, the first time I try to use the remote after it's sat for many (not sure how many) hours, it doesn't work at all, I must use the key. Seems like after about 5-7 hours of sitting it doesn't work. And, if we park it in the sun, the time gets shorter. Now, we live in Arizona, so it's really hot right now, like 111-114 degrees and it's in the direct sun, so it's more like 130 degrees. I have thought a lot about this. I'm thinking it is as you say, the starting 12v battery that is losing charge either from the extreme heat or cold. Then it would make sense that if the car sits for a while, and the battery does hold a charge for long, it would be a problem because after a few hours the voltage would drop. However, if you run the car, which charges the battery with the alternator, and use the key fob before the car battery loses much charge, the fob still works.

I'm very interested in your results. I'm hoping we will find that if the battery is fully charged to over 12v it will work fine,....and when it drops below 12v we will see the problem. Thank you in advance for posting your results, can't wait to see them.

 

As I'm waiting for the moderator to approve my previous comments, I called a local exclusive Toyota service shop and went out to the garage and tested the voltage. The Toyota shop said they don't really see this issue often and he guessed that it was something to do with the 12v battery not having enough charge. His comments were completely unprompted by me. He said when that battery gets low, all kinds of electrical things get "jenky" including lights on the dash and a/c issues. What I found with my car immediately thereafter was weird. It was sitting overnight, so I expected my remote not to work. I tried it and it didn't. Stuck my hand inside the driver door handle and it also didn't work. Both were expected, so far so good. I popped the hood and tested the 12v battery using the jump ports under the hood. The meter bounced around a bit until I found a solid ground-point. Once I did, it read a steady 12.7 volts. "Darn it", I thought, I was hoping it would be below 12v. I put the cover back on the fuse box, dropped the hood and just for grins, as I walked away, I pressed the "lock" button on the remote. It worked. Why would it work now, nothing (theoretically) changed. What??????

 

When I had to get that close to unlock the car it was the battery in the keyfob. The car was even trying to tell me it was low. It would beep once inside the car when I turned it off. (See owners manual, low smart key battery)

 

Thanks Skibob, we bought new key fob batteries yesterday and I'going install them today. We just started having all the issues about a week ago. It will be awesome if that fixes all the problems.

 

Both of those things tend to indicate a bad main power cable connection.
Most likely the negative cable, either at the battery or at the frame "ground" point.

Intermittent power connections do not follow any rules.

 

Gents, I'm somewhat embarrassed but fully relieved to report that replacing the FOB batteries with FRESH ones did the trick. We replaced them recently, but apparently they were low on charge when we bought them. We bought fresh FOB batteries (checked the date on them), replaced them and everything is back to normal. It does stand to reason that those silly little watch batteries are not "hot sellers" and likely sit in their package on the store shelf losing their charge before being purchased. Anyway, our smart keys now work well and the range in the FOB is better. Chaosphere, I hope you find and remedy the problem easily and quickly.

 

Fingers crossed it works for you. Seriously, I can't believe the CR2032 batteries we bought (2 of them) were low from the store and that caused all the problems,....took a couple months for the problem to show up, but seems like that was it. The fresh batteries made all the difference. Good luck!