Intermittent P Lock Malfunction

Consider replacing the transmission ECU under the AC unit on the passenger side.

 

Welcome! Intermittents can be such a pain!! Sounds like low voltage in the 12V system to me. Perhaps either something draining the battery when the car is off or else not driving far enough to keep is charged. After you drive a ways, the voltage gets high enough to turn off the alarm.

The "more often when it's raining" part would lead me to make sure water isn't accumulating in the battery compartment. While Gen 2 is kind of famous for leaking in that area, I don't think Gen 3 is necessarily immune.

 

iirc, soetimes the wire connections to the ecu can corrode

 

Water does leaking into battery compartment in Gen 3 Prius, I found water in my 2010 fix upper I recently purchased and drained the water by clean out the drainage grommet..
But I'm assuming it's the same issue as Gen 2, will look into it soon.

I have experience P-Lock when low voltage in 12V battery, you may want to check battery voltage if you haven't been driving it much..
And of course, I would also looking for corrosion in area related to 12V if there's moisture and other related components if all else failed..

Good luck!

Posted via the PriusChat mobile app.

 

Connect Techstream and ask it whassup?.

You'll be able to see freeze frames of what key voltages and P lock motor parameters were from the most recent time (maybe even more than one time) when it set a trouble code.

Connector and wiring issues are not out of the question as possible causes. The freeze frame voltage readings will give you ideas.

 

This conditions just screams "low battery" to me. Next time you drive after the car has been sitting for a few days, reach in from the passenger door and pop the hood. Then put a meter on the jump points in the fuse box. I'm 99.99% sure it'll be under 12V. @ChapmanF has great advice in having you connect Techstream to see what's really going on.

 

yes, toyota has the software, hopefully, they checked for trouble codes. but with dealers, who knows?

it's not a hybrid battery issue. check the 12v health, even though new, might need a charge.

i got the p-lock after washing the car once. sure seems like a moisture related issue

 

About the same odds as a dirty windshield causing it. That component is powered by the 12V battery.

Let me repeat. This is most likely a low 12V. It happens a LOT. Or maybe something with the P Lock mechanism or the ECU that controls it. Check the 12V first. That's the low hanging fruit. Takes about a half a minute. If it's well over 12V, then break out the code reading equipment. If you'd done that right away, you'd almost for sure know by now what's causing it. Stop fretting over your 7-year-old traction battery.

 

after you take thereading again, turn the headlights on for 30 seconds, and see what it drops to

 

I have Prius 2010. Now facing the same P Lock error for the past few weeks. After reading all the above threads, i also replaced my battery but that evil P error is still there. Even the replaced battery is perfectly fine. I have also get it checked quite a few times but that P error is now getting on my nerves.
I have also tried to remove the 7.5 fuse from the switch box but P error is still there.
Whenever P error appears, I simply apply the parking brake and turn the vehicle off. After 5 minutes wait, i turn it on the vehicle and every back to normal like nothing would had happened.
Please help me out. May i need to replace that 7.5 fuse or connect some cable between the 7.5 fuse to blue wire. Or what.
If anyone know the permanent solution of this problem, please do let me know
Let me reiterate that 12V battery is perfectly fine.
HELP needed.
SOS

 

Through different experiments, i have finally learned that this error has something to do with the horn. Whenever i use horn at idle mode, this P error appears. There is a chance that the Horn relay/fuse is not working properly or malfunction. I guess, at idle mode horn is consuming more current than usual. Owing to this reason, Parking motor is not taking required current level. Anyway, i will find out in a couple of days.
Btw you have rightly pointed out that this P Error has some connection with Horn. So lets see. Anyway, thanks for your help.

 

All fuse and other devices/accessories should be checked as some component is consuming more current than usual. After my detailed deliberations, i will post my final findings soon.
Meanwhile those who are facing the same problem, please check all the accessories and devices attached to the vehicle and check their voltage consumption. Check all the Fuse and Relays in switch box located in the engine and recheck consumption levels. This error only occurs when battery suddenly drops the Volts. It doesn't mean that the battery is malfunction. Do not replace 12V battery without checking the fuse and relays.

 

If you do a youtube search for intermittent P lock malfunction on 20XX Prius, you'll
find several solutions.