No Ready, No Start - Yet Battery is over 12 volts

Can you help please ?

My Gen 2 has refused to start 6 times over the course of the past month.
(Chilly, but not freezing mornings - lowest was ~ 38-40 degrees F)

But it will reliably Start after a 2 or 3 day rest.

The previous 5 times it has come back to life
when I let it sit for a day or two (or three)
AND do the battery-lines Short-out trick / and or
a Master Reset - but only after sitting a day or so.

Either trick only "works" after a day or so waiting
after first failure to start.

Or more likely they're a coincidence, that's not working
at all and something else is curing the problem. This is likely
because it started this morning after 2 day rest from the 6th failure
with neither battery-lines Short-out trick / or a Master Reset !

12 v battery is not great, but @ at 12 .3 volts (static; not under load)
should be adequate for Starting. Using a Jumper battery (12.4 volts)
ONCE - SEEMED to bring it back to life, but only once in 5 times.
And that instance could have been a coincidence.

Have not been able to do a 12volt load test.

Scanned it --
Misfire on #1 & #3 DTCs

I changed the plugs (runs smooth now and mileage has improved - nice.)
and scanned it again: Misfire on #1 & #3 - DTCs are now gone.

The only other code seems unrelated:
DTCode: C1242 "Open Circuit in Ignition 1 Ignition 2 Circuit"
I don't have the detailed Code - e.g. 87 or 88.
This seems to be the ABS (Anti-lock brakes) - rather than Ignition indicated ?

There is no illuminated ABS Light or Brake light on Dash.
The AM2 Fuse is Fine. I pulled it and reseated it.
If it was failing - why would the car eventually start ?

Do you know what C1242 really means ?

HV Battery is nearly full when I last turned it off yesterday.

Horn works, Lights work, doors lock and unlock. Just no Start or Ready.

Odd tell-tale: Smart-key doesn't unlock when I approach car.
95% predictor of whether it will start. When it doesn't autounlock
there is a 100% non-start.

When I hook up Jumper battery (12.4volts) - sometimes I hear the grunts
and squeaks that precede a successful start. Usually no noise at all.

I've read all the posts with "No Ready" and "No Start" for my Gen 2.

Which was where I learned about how to try most of
the different variations of "Master Reset."

With FOB in slot (All my Jump Start attempts are with the FOB in Slot)
(Remote Key Start button off - meaning pushed in)) and don't use FOB to open door -

1. Do NOT Step on Brake while holding Power button for 30 or 45 seconds

2. Step on Brake while holding Power button for 30 or 45 seconds,

3. Do #2 above and Continue stepping on brake while releasing Power button.

I do hear the grunts and squeaks when I press Power button with Brake depressed.

Just no lights or anything else.
Except Key/FOB Icon light does go on if FOB is not in slot.
That Key/FOB Icon light light goes away with FOB in slot.

Update: I did start it up this morning - and No codes anymore
using "Torque" scanner.

Only other things of note:

1. The first time this happened I did the battery-lines Short-out trick.
(unplug the Red Battery. Take the now "dead" wires and short it with
the Black wire. Shorting it with the Multi-meter it usually shows
over a volt and then over the course of an hour winds down to .04 volts.
Oddly when I directly short it - After going down to 0.00 volts - it
then always begins Climbing ! to 0.05 or move volts - with no battery hooked up !?!))

2. FOB Battery is a bit low - 2.3v - But it normally changes
Start Up from "Need FOB Dash Light" to No Dash Light for "Need FOB in Slot"
I will get a fully charged new one today.

3. Inverter Coolant was a bit low. But I've topped it up.

Still no joy.

My remaining best guess is that
because it always works after a couple days rest,
because the jumper battery doesn't work (it normally
has been plenty good as I've done a few jumpstarts with it) --

* Maybe the computer is getting confused and needs a Solid Reset.

I think I'm doing the reset correctly, but have no way to
verify it is really accomplished.

Or maybe its an intermittent Relay ?

What should I be testing or looking at to Diagnose this correctly ?

Thank you.

 

Responses Interspersed Next to Questions.

Q: Welcome to PriusChat!!

A: Thank you for your Welcome.

Q: Which OBD2 device are you using to scan with?

A: A fairly standard EML327 Plug and as I mentioned the Software is Torque (Pro) .

Q: What is the 12v reading at the front jumper points under the hood, for both the start and 'no start' conditions?

A: Good question. Front jumper points under the hood last check was 12.3 volts - for No Start.
I didn't think to test it when I did get it started. Next time.

Observe: Check the 12v ground strap to the body, there could be some rust around the connection point, and it may need some sanding.

A: I was getting 12.36 at the battery in the back and fluctuated around 12.29-12.31 in front.

Opin: Grab and install a fob battery.

A: Did that, didn't make any difference in starting. Did make the autoDoorUnlock more reliable.

Here is the workup for DTC C1242 : (Deleted because Blog software won't let me reply with a link in my response)

A: Thank you.

 

A: I did everything I could get out of the Repair Manual, it was only after that, that I resorted to posting here.

Thank you for your reply.

 

Good news ! Its fixed - Starting Fine.

1) Doing a 12v Battery load test by turning on headlights showed the battery was quite weak; the
headlights dimmed quite a bit. (I couldn't do a multi-meter load test, because I just couldn't juggle
- holding 2 leads in the Cigarette plug while pushing on Button (3 hands needed)
AND watching the Meter reading.)

2) Choking down the price of a new battery was too much ($219 to over $500 !!! - for a small 12 volt battery !!!) ,
so I looked into reconditioned.

From suggestions I found here - I found two relatively nearby places which had reconditioned
Group 51 and 51R for under $40.
OK - lets go get one.

When I showed up the guy correctly says - "Whoa, that's a S46B24R (or whatever number he said)
"You'll have to use adapters to connect it up.
"But you're lucky - we have just one S46B24R left and we were debating whether to keep it in stock."

Well, he load tested it with a (not-cheap) battery tester and it came in at 299 cranking amps.
(Didn't test the outgoing one - which would have been helpful for all of us in the future - as
it was right on the lower edge of working.)

Well, how much - I asked braced for the worst? When he replied $32.95 - I almost fell over.
That's almost as much the tax alone to buy a New Battery from Toyota !

So, quickly, before he could change his mind - I pulled out the old
and popped in the new - and it started correctly, and starts reliably -
every time so far - and its been 2 days. Seems to be fixed. Yaay.

The business is Interstate Batteries and I think they have shops all over the US.

Thank you PriusChat volunteers for your kind and thoughtful suggestions.

 

Ok, Bad News.

The new (reconditioned) and fully charged, load tested at (299 CCA) battery
and new (3.4volt) key FOB battery did NOT solve the not starting problem
as I was hoping.

I drove around for 2 or 3 days quite happily and confident - and then, Friday eve,
just like before - it refused to start.

Until I let it sit for 2.5 days and did both --
1) the unhooked battery cable short-out trick - let it stay shorted for 30 minutes.
2) the 30/45 second Master Reset.

This time I was able to get some readings (at the front) while it was running.
12.4 volts when car is powered off. (The unhooked up battery is also 12.4 volts.)
13.8 volts when when car is powered on.

Odd thing - with a meter on the shorted cables it would measure
0.89 volts dropping slowly to 0.04 volts.
If I merely shorted the cables out for 30 seconds or so - the voltage
would start at 0.00 and slowly CLIMB to 0.04 volts.

And No Codes at all any more using Torque Pro and a standard ELM327

Can anyone help me understand more clearly what "DTC: C1242/42 Open in IG1 / IG2 Power Source Circuit" means?
That was the code I got previously - but now is gone.

Anyone ever have a bad or intermittent relay or fuse doing something like this ?

I am open to testing any ideas.

Thanks.

 

Battery replaced, tested at 299 Cold Cranking Amps - still failing to start randomly.

 

Thanks for your thoughts on an alternative battery.
Yes it is a Professionally Reconditioned Battery.
That is substantially different than merely "used."

My Prius has been starting for years with a whole lot less than 300 CCA, more likely in the neighborhood of 100 CCA.
So its hard to imagine that is the problem since this one charges to 12.8volts @ 299 CCA.
Cheers.

 

Thank you for your ideas.

There could be a parasitic drain, but its not starting even with a
truck Jumper Battery with 13.2 volts and 600 CCA.

Yes, I was amazed to find those reconditioned batteries for a reasonable price (under $50)
They come with a 6 month warranty.
And as long as this one charges to 12.8 volts as it is doing yesterday, I'm confident it is not the 12v. battery.

Couple of old time mechanics weighed in today.

1) Maybe the key system isn't recognized (Thanks Patrick),
and
2) Did I reseat the HV Battery locks because they can corrode (I live within spitting distance of salt water. Thank you Louis.)

A: Haven't had time to pull out all the rear seat and stuff
to get to the HV Battery "locks", but maybe tomorrow.

The key / Immobilizer system & antenna is good guess.
However as I mentioned above - the starting system works most of the time.

So that means they key does work - sometimes.
(A locksmith tried to charge me $420 to make me a new Prius key (how generous)
even guaranteed it for 6 months. Problem is - unlike his promise on the phone
he had no way to test my key, or the immobilizer system. I passed.)

It just stops working every 2 to 3 days.
Then I have to wait for 1-3 days before it deigns to start again.

Today was the first time it started in less than 24 hours after a hard fail.
It was some combination of pressing the SKS button in and out
while pressing the Power button, over and over in as many combinations as we could think of.

Then Surprise - It Started !
(That was hard fail # 8)
And it was less than an hour after the locksmith left.

Anyone have any experience with the Immobilizer Antenna going bad, or getting corroded connections
or a FOB getting Un-Programmed by accident ?

Thanks.

 

OK, I'm feeling more confident to report that the Prius is starting 100% reliably
since Feb 28th. That 11 days is by far the longest stretch of starting
since this problem began some 2 months ago.

Here's my latest observations on what may have changed to have it starting now.

1) The locksmith did do one thing while he was trying to sell me a $420 key.
He took my key apart: sprayed it with some liquid, presumably an electronic cleaner.
Then while it was still wet, he brushed it with a toothbrush.

2) After he left another Prius owner came by and kept trying to start it by pressing all the Key buttons and pushing the SKS button on and off while Pressing the dashboard Power button. He tried for 10 minutes. Then just as he was about to walk away and wish me good luck - he asked to try it just one more time.

Amazingly this time - he got it on as far as the Non-Ready Accessory mode.
Since I'd already gotten a full start from this point - I was thrilled.
Asked him to jump out. I pressed Power again with the Brake pressed
- and Presto - Ready and ON !!!

Thanked him profusely and drove away deeply relieved.

Other than that - no changes in the system that I can think of.

Was a Key button tuck on (or off) and interfering with the immobilizer radio
or the on-chip system ?

Which of these do you think worked ?

Maybe both.

In any case - I appreciate the thoughtful comments here. Thank You !

 

Do you mean stuck switch in the Key Fob - or somewhere else?