Replaced fuse box housing - transmission "P" lock mechanism appears

Brought a rebuilt 2007 Prius and have been driving it for about a month while replacing a few parts.

The fuse box housing was cracked from previous hood damage, so I picked up a replacement fuse box from a junkyard. I did not swap the actual fuse box electronics or connectors, only the plastic housing.

The process was simple. I unclipped all connectors from the damaged housing, slid everything out, and snapped it into the replacement housing. Everything went back exactly where it was.

After finishing, I reconnected both the 12V and hybrid battery.

The car powers up fine, but now I get a red triangle warning and a message on the display saying there is a problem with the transmission "P" lock mechanism.

Here’s the strange part. There is no check engine light and no trouble codes showing. The car shifts into Drive, Reverse, and Park normally and drives perfectly fine.

I have checked all fuses and everything looks good.

Has anyone run into this before or have any idea what could cause a "P" lock warning when everything seems to function normally?

Thanks in advance.

 

I plugged in Techstream and here’s what I found so far.

The initial codes were B1210 and B1271, which appear to be related to the Gateway. From what I understand (and what AI suggested), these don’t directly cause the “P” warning but may indicate the ECU isn’t fully satisfied with system conditions.

I then checked the Hybrid Control system and found code P0A0D (High Voltage System Interlock Circuit High). I’m not entirely sure how to interpret that yet, especially since the car still drives fine in both Drive and Reverse.

One thing I did notice while testing: a few times when I shut the car down and restarted it, all the warning lights came on and the car would not go into Drive or Reverse. After shutting it down again and waiting a bit, it would start normally and drive, but the “P” warning still shows.

Still scratching my head on this one. Any thoughts would be appreciated.

 

I can't remember but I will run the test again with car ready on and report back.

Thanks

 

Still at work, but on my lunch break I did a little research and it looks like this might be a common issue with the P lock and fuse box. Some people are finding corrosion on the terminal for the 7.5 fuse that feeds the P lock.

A few said they fixed it by adding a jumper wire from the fuse to the connector that goes to the P lock module.

When I get home, I’m going to check the voltage on that wire to see if it’s getting power.

Has anyone else run into this issue, and was that the cause?

Thanks

 

I only replace the housing. no wires.

 

Tonight I added a jumper wire and it initially removed the P lock warning. However, as soon as I shifted into Drive, the P lock warning came back on the display. When I put it back into Park, the warning went away again. So it feels like I am getting closer.

I was able to find a wiring diagram online, so my next step is to study how that 7.5A fuse is connected and what circuits it feeds.

I also looked at the wiring on the junkyard fuse box. The wire appears to be the same color and gauge, but it does not seem to connect directly from the 7.5A fuse to the pin on the top connector. Instead, it runs into the harness. Unfortunately, I had cut that section when removing the fuse box from the junkyard car, so I do not know exactly where it routes or connects.

I am hoping the wiring diagram will help me trace the full path of that circuit and figure out where the break or missing connection might be.

 

I went ahead took fuse box apart again and found something interesting.

Taking a break to post this photos.