Where exactly is the transponder on 2005 model?

Okay. I had power issues with my prius about a month ago. Swapped psc, it began working a week later so psc was not the issue However it's once again not working. Next step in service manual is to test connection between transponder and psc. I believe my transponder is malfunctioning due to moisture. I just need to know where it is, i cannot find it for the life of me.

Symptoms are On button does nothing, no lights on button. car worked yesterday. Battery is charged, the key detection symbol stopped flashing like it should. Sks smart key works for entry. I had a previous thread about this issue.

I need to know where, i read it's on the passenger side by or behind the heater. Where exactly is it and how do i access it? From above or below? My father and I took off all kinds of stuff under the dash like air ducts and could not find it when we tried a couple weeks ago.

Thanks in advance.

I have a 2nd prius with 299k that burns way too much oil and I'm tempted to swap the four ecus, smart key, transponder, hv and ecus if cleaning my vehicles transponder board off doesn't work.

 

Yes the vehicle has sks, keyless. The sks system works for opening doors like normal. The immobilizer aka transponder key ecu is what I'm trying to locate and how to exactly access it.

My dad has alldata from being a chrysler tech and we see it's basically behind the center air vent but cannot find it. Is it on the firewall? Is it buried by the heater?

 

Voltage off the front jump point is 12.4v

Basically this afternoon i went to the car, immobilizer/security light was flashing like normal. I pressed the button and the light went out, vehicle did not start.

I unplugged 12v ground and now a couple hours later went outside to measure front jump point. The security light was flashing like normal, pressed the button and the light went out, no start.

Im asking for details on transponder key ecu, like is it under the heater? On the firewall? So i can go to the next diagnostic step. I have the alldata diagrams but i do not see it behind the vent, nor like against the firewall.


My goal is to try cleaning the transponder key ecu as it's not a sealed unit.

I have a worn out donor prius. I can basically pull all kinds of stuff off, i just can't swap the transponder key ecu if i can't find it. When i last pulled codes when it wasn't working the can bus was down if i recall.

 

It's not a loose connection. At least not at the 12v. It's secure, dash gets power. Once i press the start button the security light goes away. It still shows the door ajar symbol, etc. I measured front jump point at 12.4v. Headlights work, keyless doors work.


The car had the famous trunk leak a few months ago with our crazy rain. Then on a hot day the car looked very humid inside, i aired it out with a fan and a week or two later this issue occured.

After leaving it with the dash out for two weeks in defeat the problem went away. I swapped the power source control module but it did not solve the issue.

I removed the 12v ground connection earlier for a couple hours, and the light came back flashing like normal. However pressing the button causes the light to go out.

While the dash was taken out we cleaned all of the major grounds we could find.

 

I unbolted it. I apologize for my terminology. I was more focused on describing the issue and not the ground connection description. I assure you i understand which connection is the ground and that the positive has a plug under the red cover near the voltage sense wire

The issue is not related to my 12v battery connection point.


Previous codes during this issue was b2287, b2289. I put over 200 miles on it until this just showed back up.

Power source control ecu is good i even swapped it with a known good part. Next step according to the manual is locating the transponder key ecu and testing between the two connections.

 

I found the answer regarding the key transponder aka engine immobilizer ecu. I hope this helps other people as the question has gone unanswered and poorly answered in many posts.

It's not in the right center of the dash above the junction like the diagrams lead you to believe.

It's directly behind the white hvac box that leads up from the glovebox against the fire wall. To access it, you remove the dash like normal. Then remove the black duct tubes. Use a ratchet and extension to remove the single 10mm bolt.

 

Swapped am2 and sadly did not fix the issue.

Reconnected battery and the immobilizer light isn't coming on again. Door ajar light works. I'll pull the dash back out in the next couple days and test the connection between psc and key transponder ecu per the manuals diagnostic flowchart. I will also use contact cleaner on the transponder ecu, as it is located close to where all the humidity was building up on the dash and is not sealed.

Once i have the grounds tested and harness checked for corrosion and shorts between connections I'm likely gonna pull the all the required ecus out of my worn out(and working) 285+k prius to swap into this 146,000 mile prius. It's like 4 ecus that are needed to swap the whole immobilizer system. Both cars are sks.

If that doesn't work i give up on it. Also tempted to swap the body ecu(which is the fuse box/brains on drivers side) though the autel said it was working properly. The manual says the body ecu controls the light lol

I'm tempted to pickup a cheap laptop and mini vci cable but i'm honestly tired of putting money into this thing. I can junk the car with the lithium nexcell battery removed(and sell private party or horde)for $800 to a local prius place.

I'm hoping one of the ecus is moisture damaged and swapping them from my donor prius solves the issue or we find a corroded connection. If so I'll pickup a replacement set from ebay, i see people selling all the required ecus with smart key from used priuses.

We already cleaned the 2 or 3 major ground points under the dash that we found with a wirewheel. This weekend is gonna be my last attempt with my dad, a mastertech, to solve this. Otherwise someone else can try figuring it out

 

The autel i was using can only see 5 modules on a 100% functional prius with the vehicle not powered on.

The autel on the broken prius shows an error with the psc. Giving codes b2287 and b2289. It only shows 3 modules. Body ecu, smart key, and psc.

Psc has been swapped. Next step in service manual is to test connection between psc and immobilizer ecu(transponder key)

I bit the bullet this morning and ordered a mini vci cable and an old lenovo thinkpad windows 10 laptop from amazon. Comes tonight. I'll setup techstream and find out.

You're saying techstream can in theory communicate with every module even in an off state?

None the less techstream is better than the autel so hopefully it'll help diagnostics and hey maybe my 2010 camry will need it one day.