Power button does nothing. Car worked a couple weeks ago. 12v is fine.

Alright guys my first thread on priuschat. I normally lurk. Tried searching to no avail.

Gen 2 prius. Has lithium pack. I haven't been driving it much lately and generally start it every couple weeks to cycle the system and keep the hv battery happy.

Today i unlocked it, made the normal brake sounds when depressing the pedal. Power button is doing absolutely nothing. Sks system works, dash is displaying nothing, it's like the button is broken.

Checked 12v connections, removed to discharge system and reinstalled. Nothing. Locks work, headlights work, i even tried jumping it. Power button does nothing, no lights zilch. Removed HV safety plug and reinstalled correctly via locking it downards.

Checked am2 fuse, checked giant fusible link. I do not understand what is going on. Any suggestions?

Would a drained HV battery cause the dash to have zero response? It's unlikely in my mind but i have a maxxvolts charger. However i don't think the pack is drained as i run it for a couple hours every time i start it.

Once during my thousands of button pressing the car displayed no key, but only for a very short moment. I cycled sks system on and off, tried inserting key, the button is doing nothing. Any suggestions?
Thanks i appreciate it.

 

I 100% installed a nexcell pack, i am not mistaken on this lol. I got it march of 2022. I have a maxxvolts charger from my previous nimh pack. I haven't used it on my project lithium pack but the harness is there.

My 12v is fine, reads 12.2volts. It's a wheelchair agm. I'm mechanically inclined but this has me stumped. I have no low voltage symptoms. Headlights work. Sks system works. Start button does nothing. Checked most of my fuses, 12v battery connection, 12v battery side fuses. Etc.

 

Connecting an auxiliary battery makes no difference in the 'no response' condition. I first tried jumping it via a 12v motorcycle battery and even tried using my camrys 12v, along with a jump pack which shows 12.2 volts on my wheelchair agm.

Fob is working, keyless entry is working, if my fob was dead the car would display the no key symbol when pressing the start button. I wish this was my issue.

 

Fob also shows red illumination light when removed from ignition.

 

My camrys battery is fine. The 12v ground is tight against frame, as is the connection to my battery. Headlights work, brakes prime like normal, sks system works meaning keyless entry/unlock is functioning. Car locks when pressing the black button on doors. Even with key inserted the start button results in zero lights or effect.

Giant fusible link is intact. I've checked it over multiple times. Car worked fine couple weeks ago. I'm stumped by this issue.c

 

I'll check pack voltage today. Combo meter is not turning on. Pressing the power button does absolutely nothing. Zero sounds. Zero effect. Combo meter was working prior. Car is kept outside. Never had rodent issues but i guess it's possible.

 

I don't believe i can read codes(have correct elm1327) without the car powering on. The button is un responsive.

Only thing i can think is moisture or something. We had a lot of rain, now it's been sunny.

 

Car does the same thing with external power source, same with jump pack. Should still boot up.

 

As in the ecu under the dash behind combo meter?


I found the old thread where you helped someone diagnose a very similar issue in 2019. Lots of good info in it, including sam spade and his 12v not being fully charged rant lol.

Thanks I'll follow through it, the schematics are very helpful.


I noticed moisture in my cars dash combo meter display case after the couple months of rain that fed some water into my spare tire well. I fixed the hatch weld leaks with silicone. The moisture showed up once the rain ended and warmer temps began. I know this basically opens pandoras box but it seems the power source ecu is indeed located right there.

 

I haven't pulled my dash to meter stuff yet, noticed this issue yesterday evening when i went to start the car for routine battery maintenance.

I don't believe it's the button, as during my thousands of button pressing, I've now seen twice, a no key symbol display for a split second(no beep. Key wasn't inside vehicle either)Both times my key was not in the ignition. Also the moisture first collected on the windshield, which i tried removing via ac, successfully i thought. Then i later saw it in combo meter.

I haven't been able to replicate the key/no key issue. It once occured randomly, other time i had just disconnected the white connector in front fuse box and reinserted.

To answer other questions:

Power button has no lights on it when pressed(it's outer ring is illuminated, like the key slot)car does the normal sks stuff like turn on interior lights and activate brake acuator when walking by.

They're no dash lights being triggered for key/no key. Only the time i saw them for a split second(no key) but haven't been able to replicate it.

The normal door ajar lights display.


Based on the toyota diagnostic info posted in the previous 2019 thread I'm going to check am1 fuse under dash/parking brake area. If am1 is fine, recheck am2, check all button related fuses,check power button, if button is good, going to throw a power control supply ecu at it as it's what the power button actually initiates. They're about $20 on ebay so not a huge loss.

This is the only logical failure(psc ecu) outside of wires being physically broken. Every other module, whether hybrid related or actual ecu/ecm is powered through the power control supply ecu. The car would still boot up and display a check engine or other error.

If the button was bad i don't think it'd of displayed a no key symbol for a super split second. This seems like a module issue to me. As normally the no key thing is displayed for a couple seconds and iirc illuminates the button.

 

Some useful info from tmr jwap in an old 2018 thread


Out of curiosity, have you checked to see if the AM1 fuse is good? Maybe even pull the fuse and make sure it has 12v on the supply side of the fuse?

AM1 fuse supplies power to the push button start system

Also supplies the interior lights, shift control and is a supply to the hybrid system

Actually, it looks like a bunch of fuses are listed as supplying the push to start system

In engine Compartment Fuse Box:
7.5A P CON MAIN
15A AM2
15A DOME
20A HEV
30A P CON MOTOR
100A DC/DC
7.5A ACC
7.5A AM2

In driverside interior fuse box:
7.5A ECU-IG
7.5A IGN
7.5A STOP
10A Gauge
25A ACC-B


All these fuses have "Push button start system and vehicle immobilizer system" listed as items they supply"

So I'm gonna check these fuses, if all good, will order a psc off ebay today.