Need Help: Doors won't lock/unlock

There is no "diagnostic" that will accurately test the 12 V battery.
IF.....it is the original one, it is due for a replacement because of age, regardless of what any tests say.

Start there. If you do NOT, you will be sorry for the time you wasted.
12.0 is NOT sufficient. That indicates it is at about half capacity.
And the other seemingly unrelated things that all showed up at about the same time CLEARLY makes the 12 V system suspect. If not the battery itself, maybe a loose or corroded main connection.

P.S. I also think that you do NOT actually have a C.
I don't think the C dashboard EVER looked like the one you have pictured.

 

Theoretically yes.
Theory is often found to be false. But if that is the easiest thing for you to try, by all means give it a go. Just don't come to any conclusions, unless the door locks work while the charger is on the 12 volt battery.
Still a good idea to get the codes logged in the Engine Control Module.

 

Yes but leave the charger connected for at least an hour before testing.
If the charger has a capacity of less than 2 amps, then 4 hours.

 

Sam, Luis didn't produce that youtube, it's just the reference he used for instructions on doing the voltage self-test.

@Luistorna1994 That's not a perfect test in the sense that the car has to be booted up, so it is drawing from the same battery it is trying to test. However the readings you are getting are low enough to make me think this battery is at least part of the problem. It doesn't perfectly explain your symptom but it is plausible. If the voltage is going low enough to trip ABS alarms it's past time anyway.

If I remember correctly the only tools needed for a battery swap are a philips/JIS-head screwdriver and a 10mm wrench.

It takes all of 10 minutes to swap, though it sure helps if you don't have to do it on the street. They aren't easy to get- only Toyota dealers stock the exact replacement.

Now, once a new battery is in there I don't know if you can expect instant restoration of your wireless security or if anything else needs to be reset. I would not anticipate needing to reset anything. I have disconnected the 12v battery in my own c several times and never needed anything extra for the lock function.

 

If you do get a new battery.......and change it yourself.......be EXTREMELY CAREFUL that you don't short anything out in the process (disconnect the negative cable first and reconnect it last).
And be sure that you don't connect the cables to the wrong posts.
And be sure that your "new" battery is fully charged BEFORE installing.

 

Attach it to a small automatic charger until the "charged" light comes on......or until the "charging" light goes off.
Or ask the place where you buy it to charge it before you take it. I tend not to trust them though.

 

batteries are expensive, so be prepared for that not to be the problem, but still a good investment.

to charge the existing battery, you would need to buy a smart charger. jumping it from another car won't charge it up.

 

You can put a voltmeter's probes on the battery posts while it's sitting on the parts department counter and your money is still in your wallet. They almost certainly have a meter, or you can bring your own. Even the $6 harbor freight one is good enough. Fully charged and then left to rest more than 4 hours it should show ≥12.6 volts.

Of course you could get a charger and top it up yourself, but how much stuff do you want to buy? They should be able to sell you a charged battery.

I wouldn't be shocked if the meter says its low and they have to take it around back and charge it though.

 

I see your greater than sign.......but a fully charged AGM should read 12.8.....minimum.

 

You are correct, I looked up the table and read from the flooded lead acid column instead of the AGM column where 12.60 equates to 75% charged, not 100%.

I still might recommend 12.6 as a helpful buy/no buy threshold for a countertop test in a store since they probably haven't had it on a charger for a while.

Of course they're supposed to do maintenance charging on the inventory, but not all of them do it and the consequences don't add up to much beyond making it harder to find one that scores a perfect 12.8+.

 

the car won't charge it up, only maintain it. you risk future problems because you have less buffer

 

You might but I would not.
ASSumptions often get you into trouble.

 

NO.
In some circumstances, once in the car it would never come up to a full charge.
If it is 90% charged, that should be OK.
If it is 70% charged, that likely would NOT be OK.
The problem IS that you have no good way to tell where it really IS if less than full.

AND....sometimes new batteries are bad too.
If it will not come up to 100% charge, you should not buy it.......but you (or the seller) will never know that if you don't try.

 

I just experienced the same issue and could not find a solution anywhere: keyfobs and mechanical key could not lock / unlock the doors. I changed the battery in the keyfobs, trickle charged the 12V battery overnight - still nothing. I removed the door panel and checked the cables - nothing wrong there. The locksmith I called was perplexed but figured it out: he removed the lock from the side of the door and reinstalled it - instantly everything worked: the mechanical key engaged the lock and the keyfobs worked again. I could not find a video anywhere showing how to do it but it was very simple - took him less than 5 minutes. Hope this helps save someone $95.