Hybrid vehicle immobilizer / Theft deterrent system indicator stays on and drains battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Mariah MacDonald, Mar 18, 2018.

  1. Mariah MacDonald

    Mariah MacDonald New Member

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    The Hybrid vehicle immobilizer / Theft deterrent system indicator for my 2004 Prius stays on after I have removed the key from the cabin and locked the car doors. Every time that this happens (it has now happened 5 times), I find the car to be dead the next day.
    The key fob seems to be functioning normally (unlocking the doors with the buttons, unlocking driver door by putting hand behind the handle, starting car without inserting the key fob into the slot), but I replaced the battery just in case. I've also tested my auxiliary battery, and it was running at 12.3V, so I'm fairly certain it isn't that.
    Is this light (and the constant searching for the key) what is draining my battery? If so, how do I disable it? I turned off the smart key system, but the light still remains on after existing the car. I was considering that maybe the antenna is damaged? But I have no idea how to go about investigating that. Please help :(
     
  2. SFO

    SFO Senior Member

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    Welcome to PriusChat!!

    How far (miles) do you drive the vehicle per day/week?
     
  3. Mariah MacDonald

    Mariah MacDonald New Member

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    Thank you!
    And it depends. When I am not traveling, it is about 70 miles per week. About every month or so, I drive trips of ~300-500 miles. Why?
     
  4. SFO

    SFO Senior Member

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    The 12v battery charges very slowly while driving or when in 'Ready' mode, 70 miles a week isn't all that much and you could be slowly draining the 12v over time.

    When was the last time the 12v battery was replaced?
     
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  5. bisco

    bisco cookie crumbler

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    what do you do when the car is dead?
     
  6. Mariah MacDonald

    Mariah MacDonald New Member

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    I just get a jump from someone. The diagnostics screen of the car says the 12V is doing fine, though.
     
  7. bisco

    bisco cookie crumbler

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    does it actually say 'doing fine'?
     
  8. jerrymildred

    jerrymildred Senior Member

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    Welcome!

    The immobilizer is supposed to be on when you shut down the car and it will not run down a healthy battery unless you let it sit for weeks and weeks. So, either you're taking too many short trips and it's not getting recharged or it's not holding a charge.

    The car doesn't really do a diagnostic of the 12V. The MFD will display the battery voltage but, iirc, the car must be in ready mode for that and that would mean the inverter is charging the 12V battery, so the display would show around 14 V give or take a couple tenths. I tried that once a couple years ago just out of curiosity. But it's not helpful unless you think the charging system is malfunctioning.

    You said in your original post that you tested it at 12.3 volts. Was that immediately after shutting down or had it set overnight? Either way, that's a little low but especially if you just shut it down. If you put a load on it like headlights and got that reading, that's not so bad.

    One more thought. You didn't say how long you've had the car. If it's new-to-you, there may be something that the previous owner installed that's draining the battery.

    Also, please be hyper careful when jumping a Prius. Getting the cables reversed can cost thousands of dollars in damage to the inverter system.
     
  9. exstudent

    exstudent Senior Member

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    1) Your method of getting the 12.3V battery reading is suspect. A load test is needed. Follow post #5 below.
    Is my inverter coolant pump slowly failing? | PriusChat
    Post 5-quick easy way to load test the 12V battery
    Post 8-SOC (State of Charge) chart, some smart, AGM compatible 12V battery chargers.​

    2) How many times have you had to get a jump, and over what time period? You give the impression that this is multiple times. A discharged battery will live a shortened life, which is probably your battery's case.

    3) 70miles/wk ~ 14miles/work day, may not be enough. 14 miles/work day in Los Angeles would be sufficient, as that short distance could easily be 1hour+ in traffic = 1 hour+ for the 12V battery to get charged. A better gauge is how many minutes/hours is the car in READY mode per week?

    4) Do you listen to the radio in ACC (Accessory) mode? Esp for long periods? This will obviously contribute to drain the 12V battery faster, and leave it in a discharged SOC, which will shorten its lifespan.

    5) When was the 12V battery last replaced?

    6) Should you need to replace the 12V battery , do NOT get an Optima. Why? It is a 38Amp Hour battery; you are loosing 7Amp Hour. Your SKS equipped Prius came with a 45Amp Hour battery. Also, recharge the 12V battery prior to installation; sitting on the parts shelf collecting dust can lead to the battery being partially to severely discharged.

    Get a Prius battery from the dealer; price shop this, ask for discounts (AAA, Costco, etc), dealer coupons (online, mailers, other dealers
    Camelback Toyota has it for $183.65, 7 year pro-rated warranty; no dealer can ship it, as it is it is considered Hazardous Material, and would require cost prohibitive Hazardous Material Shipping. Maybe your local dealer will price match Camelback?
    2007 Toyota Prius Parts - Camelback Toyota Parts - Genuine OEM Parts - Free Shipping

    A Bosch AGM Prius battery is a great buy from PepBoys. $142.49, 4year straight warranty; not pro-rated, same 45Amp Hour capacity, fits the Gen2 Prius, has the vent tube hole, and JIS battery terminal posts (IIRC). Hopefully there is a PepBoys near you.
    Car Batteries | Auto Batteries For Trucks & SUV's | Pep Boys
     
    #9 exstudent, Mar 19, 2018
    Last edited: Mar 19, 2018
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  10. Mariah MacDonald

    Mariah MacDonald New Member

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    To all,
    The car is in ready mode about 1 hour per day; four days ago it was in ready mode for 7 hours.
    I bought the car two years ago. The battery had been replaced right before I bought it.
    I do not listen to the radio in accessory mode. I don't do anything in accessory mode.
    To test the battery, I used the car's built-in diagnostics menu. Here are the values it read:
    Off 12.4V
    Accessory 12.2V
    On 14.4V
    These values were after it had been sitting for 5 hours. So not overnight, but not immediately after running the car.

    I understand that there might be something up with the battery, but that still does not explain why the Hybrid vehicle immobilizer / Theft deterrent system indicator stays on. I'm not sure how best to explain this. Yes, the light should blink to indicate that the car is armed, and yes this blinking will not drain the battery except after months. That is not the problem. The light is not blinking; it is staying on. I open the car door, the light stays on and the car starts beeping, like it does when it does not detect a key or when I leave the key in the car. I understand that the tiny pull of the light is not sufficient to brain the battery, but the constant searching for the key might be enough, especially with colder temperatures. So my question is, what would cause this indicator to stay on instead of blink? Follow-up question, could whatever this light indicates be draining the battery?
     
  11. exstudent

    exstudent Senior Member

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    12.2V in ACC mode is a small load and this battery is weak. (50% SOC at best).
    Best to take a reading with a DVM (Digital Volt Meter); borrow/buy one if you can. I think you should be able to still do the test w/ the built in menu function with IG-ON, vent fan on HIGH, NO A/C, radio on low. This will be a better load, and provide a better indication of the current battery's SOC. That 12.2 will most likely drop into 11V range or lower.

    Get the battery recharged with an AGM compatible charger. Why an AGM compatible charger? AGM chargers will recharge to a higher voltage that an AGM needs. Non AGM battery chargers will cut off before an AGM battery is fully charged, b/c regular battery chargers charge to a lower threshold, that is sufficient for wet cell and maintenance free batteries.

    1) Maybe the weakened 12V battery is the cause of the light staying on? People report the Prius doing weird things when the 12V gets weak. Recharge the battery first, then continue below.
    2) Try resetting the car by disconnecting the 12V battery ground for a minute or two, then reconnect.
    3) Maybe there is a lost FOB in the car, the previous owner(s) could not find?
    4) Just deactivate SKS?
    5) You'll need to see the dealer. The solution will be costly.

    Just a guess, but seems like the SKS ECU remains engaged all the time, and does not "sleep," like it is supposed to after a period of time when the FOB is not in proximity. Even in sleep mode, it will periodically "call/listen" for your FOB.
     
    #11 exstudent, Mar 19, 2018
    Last edited: Mar 19, 2018
  12. jerrymildred

    jerrymildred Senior Member

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    Ahhh! Now I get it. :) I'm not sure if a low fob battery will do that. Here's what I found in my wife's '07 owner's manual. If it's not the fob battery, then I think I'd take it to the shop. :(
    Screen Shot 2018-03-19 at 1.18.26 PM.png
     
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  13. dolj

    dolj Senior Member

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    While this is generally interesting information, it does nothing to address your issues. It really is a red-herring as the voltages you reported are not going to cause any faults related to a bad or irregular 12 V supply. For that the battery would have to drop well south of 10 V.

    The thought that the immobiliser or SKS ECUs not going to sleep may be relevant.

    jerrymildred has the best advise so far. I wonder if reading pages on the Theft Deterrent System starting at page 46 would shed any light or give you some more clues.

    If you don't have a hard copy of the OM (owner's manual), you can download a PDF copy from the Toyota owner's section of their website.

    Let us know if any further information come to light.
     
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