Open Back Door Sets Off Alarm

**TonyPSchaefer** · 01-17-2009, 07:59 PM

I'm posting this for a friend who explained some strange behavior. I have to apologize for my lack of complete and thorough knowledge of the whole situation. I promised him that I would post the issue for collective review. I can ask him any follow-up questions if needed.

He has SKS and apparently only the driver's door unlocks. He opens the driver's door and presses the armrest button to unlock all doors. Then he opens the back door. That's when the alarm goes off.

He says that he's tried variations but that almost always result in the alarm going off. He thought that he had found a way around it but eventually, apparently, even that started causing the alarm to go off.

All I could suggest was that he take it to the dealer and have the dealer go through the process. Other than that, there was nothing I could suggest. The behavior is so odd to me that I'm completely stumped.

What do you all think?

Patrick Wong · 01-17-2009, 08:34 PM

Hi Tony,

What model year?
What does your friend do to turn off the alarm?
After the alarm is turned off, is he able to start the vehicle?

In any event, I agree that a dealer visit is in order. Two ECUs are primarily involved in the door lock/unlock process. The smart key ECU receives the signal from the device that communicates with the fob; while the hatch and the door locks are controlled by the multiplex network body ECU. Since only the driver's door is unlocked and subsequently the alarm is triggered, this implies a problem within the multiplex network body ECU.

Since the system does not recognize the fob when your friend approaches the hatch, this implies that the luggage electrical key oscillator (outer) or the smart key ECU are also having trouble.

RobH · 01-17-2009, 08:36 PM

What condition is the 12V battery? If it's low, computers start going wonky.

**Tideland Prius** · 01-17-2009, 08:43 PM

Couldn't he just open the hatch with SKS directly?

Something's fishy. See what the dealer says.

**TonyPSchaefer** · 01-26-2009, 04:11 PM

It's not the hatch that's doing it - though I didn't ask about that. It's the rear door on the driver's side that's setting it off.

It's an '08.
I guess he hits the alarm button on the fob.

Shoot, I might ask if he'd mind that I shoot some video.

qbee42 · 01-26-2009, 04:44 PM

Is this the standard alarm, or some sort of optional package?

Tom

01-17-2009, 07:59 PM	#1
TonyPSchaefer Your Friendly Moderator Join Date: May 2004 Location: Far-North Chicagoland Posts: 10,512 My Car: 2004 Prius Model: Package: #9 Thanks: 39 Thanked 168 Times in 109 Posts Friends: 23	Open Back Door Sets Off Alarm I'm posting this for a friend who explained some strange behavior. I have to apologize for my lack of complete and thorough knowledge of the whole situation. I promised him that I would post the issue for collective review. I can ask him any follow-up questions if needed. He has SKS and apparently only the driver's door unlocks. He opens the driver's door and presses the armrest button to unlock all doors. Then he opens the back door. That's when the alarm goes off. He says that he's tried variations but that almost always result in the alarm going off. He thought that he had found a way around it but eventually, apparently, even that started causing the alarm to go off. All I could suggest was that he take it to the dealer and have the dealer go through the process. Other than that, there was nothing I could suggest. The behavior is so odd to me that I'm completely stumped. What do you all think? __________________ Proud father of Priapus: the '04 Tideland BC9 with an OEM EV button and sense of self-righteousness Current Mileage Chicago Prius Group Website Chicago Hybrid Group on FaceBook Find me on faceBook

01-17-2009, 08:34 PM	#2
Patrick Wong DIY Enthusiast Join Date: Mar 2008 Location: Green Valley, AZ Posts: 4,059 My Car: 2004 Prius Model: N/A Package: #9 Thanks: 21 Thanked 213 Times in 184 Posts Friends: 44	Re: Open Back Door Sets Off Alarm Hi Tony, What model year? What does your friend do to turn off the alarm? After the alarm is turned off, is he able to start the vehicle? In any event, I agree that a dealer visit is in order. Two ECUs are primarily involved in the door lock/unlock process. The smart key ECU receives the signal from the device that communicates with the fob; while the hatch and the door locks are controlled by the multiplex network body ECU. Since only the driver's door is unlocked and subsequently the alarm is triggered, this implies a problem within the multiplex network body ECU. Since the system does not recognize the fob when your friend approaches the hatch, this implies that the luggage electrical key oscillator (outer) or the smart key ECU are also having trouble. __________________ 2006 Highlander Hybrid 4WD-i 2004 Prius 2001 Prius (sold Feb. 2008, 75K miles) 2000 Ford Mustang GT conv. Last edited by Patrick Wong; 01-17-2009 at 08:48 PM.

01-17-2009, 08:36 PM	#3
RobH Senior Member Join Date: Sep 2006 Location: Sunnyvale, California Posts: 678 My Car: 2006 Prius Model: Package: #8 Thanks: 23 Thanked 46 Times in 29 Posts Friends: 0	Re: Open Back Door Sets Off Alarm What condition is the 12V battery? If it's low, computers start going wonky.

01-17-2009, 08:43 PM	#4
Tideland Prius Moderator of the North Join Date: Oct 2004 Location: Canada Posts: 19,633 My Car: 2010 Prius Model: N/A Package: Technology Package (Canada) Thanks: 229 Thanked 346 Times in 245 Posts Friends: 23	Re: Open Back Door Sets Off Alarm Couldn't he just open the hatch with SKS directly? Something's fishy. See what the dealer says.

01-26-2009, 04:11 PM	#5
TonyPSchaefer Your Friendly Moderator Join Date: May 2004 Location: Far-North Chicagoland Posts: 10,512 My Car: 2004 Prius Model: Package: #9 Thanks: 39 Thanked 168 Times in 109 Posts Friends: 23	Re: Open Back Door Sets Off Alarm It's not the hatch that's doing it - though I didn't ask about that. It's the rear door on the driver's side that's setting it off. It's an '08. I guess he hits the alarm button on the fob. Shoot, I might ask if he'd mind that I shoot some video.

01-26-2009, 04:44 PM	#6
qbee42 Senior Member Join Date: Mar 2006 Location: Northern Michigan Posts: 10,492 My Car: 2006 Prius Model: Package: #7 Thanks: 95 Thanked 392 Times in 290 Posts Friends: 10	Re: Open Back Door Sets Off Alarm Is this the standard alarm, or some sort of optional package? Tom

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