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2008 Prius ABS Control Module Failure - Questions w/ Diagnostic Screenshots

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Geedis, Jun 17, 2019.

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  1. Geedis

    Geedis New Member

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    Hello,

    I'm seeking advice regarding a possible ABS control module failure on my 2008 Prius. Attached, you'll find the dash lights as well as a series of photos a mechanic sent me of the the car's diagnostic report. Can you help me understand what I'm looking at? Here's some context/questions:

    • After the dash lights came on, I took the car to a trusted mechanic. He ran the diagnostics and initially told me that the code suggested a dying hybrid battery, not an ABS issue. He reset the dash warnings, and our plan was to drive the car until the battery died.
    • A couple of days thereafter, the lights came back on. I took the car back in, and this time he said that the diagnostic report showed an ABS failure.
    • I asked for pictures of the diagnostics, which are attached. In addition to the the ABS failure, these photos appears to show problems with the A/C, the transmission, and the engine. He did not mention any of these problems, but if true, I'm not sure I want to spend the money fixing the ABS problem.
    Can you help me:

    1. Understand these diagnostic reports?
    2. Understand why the first test might have shown a hybrid battery failure?
    I appreciate any help and advice you can provide.
     
  2. Geedis

    Geedis New Member

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  3. bisco

    bisco cookie crumbler

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    welcome!

    idk if that reader can be trusted with a prius. how many miles on her?

    would it be worth paying a dealer to get the correct codes?
     
  4. ChapmanF

    ChapmanF Senior Member

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    Too funny ... his Autel gadget confuses the brake ACCumulator with "adaptive cruise control". Good luck solving that cruise control leakage there. :)

    One thing worth knowing about the computers in a Prius is they talk to each other, and sometimes one computer will set a trouble code that's just for trouble it heard about from a different one. For example, you might have an engine controller code for some problem with the engine, and also a hybrid-control code saying the engine failed to start. That doesn't mean you've got any separate problem in the hybrid system too.

    The B1421 is a code you will always have if strong light isn't shining on the solar sensor at the moment you have the codes read. So it's nothing to worry about (unless you know the car was in strong light at the time).

    You have a code complaining about the voltage reaching the ABS controller. That does not always (or even most of the time) refer to the condition of the 12 V battery, but rather to the condition of wiring or connectors on the way to the ABS controller. But I won't say it's never the 12 V battery, either. You have two codes about lost communication with two different controllers. There will be somebody along sooner or later to suggest you should check the health of the 12 V battery, and this time I won't even object. :)

    I see nothing in this group of codes to suggest any problem with the traction (big) battery, and if I had to guess why the mechanic might have thought so the first time, I'd probably say jumping to conclusions without looking up the codes much.
     
  5. Geedis

    Geedis New Member

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    I sincerely appreciate all of this information!
     
  6. BLNT

    BLNT Junior Member

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    Hi Geedis,

    I had the following errors and codes (C1256 - ACCumulator Low Pressure - is a match with yours) that was all solved by replacing the ABS actuator on my 2005. Might be worth checking with another mechanic for codes to make sure the right kind of diagnostics is performed, and the real issue identified.

    ABS module errors.jpg ABS.jpg
     
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    x2 with Chap......with all the inconsistent and unusual codes in there, it would definitely be in your best interest to verify the 12v system/battery is good prior to any other "recommended repairs".

    One thing to keep in mind is the Prius is sometimes more like a computer than a normal car. The 12v system does not start the engine, but instead boots up all the computers and electronics (and various pumps, like the ABS). A crappy 12v sometimes = a crappy boot up and a lot of chasing your tail for ghost faults.
     
    #7 TMR-JWAP, Jun 18, 2019
    Last edited: Jun 18, 2019
  8. Geedis

    Geedis New Member

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    Is there a particular reason why that reader wouldn't be trusted?

    Thanks to all for the replies and info -- it's super helpful.
     
  9. BLNT

    BLNT Junior Member

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    Hope you found something useful - let us know in the end how it was solved. What I meant with checking with other mechanic is that replacing the ABS actuator might be costly and it is better to be on the safe side to replace something that is for sure broken.

     
  10. Geedis

    Geedis New Member

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    Gotcha. I'm definitely going to take it to get a second opinion.
    If the readouts look similar, my general plan is to buy a used actuator -- is there a way to identify ones that came from later years?
     
  11. Skibob

    Skibob Senior Member

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    Check the 12v voltage when the car has sat overnight, BEFORE you start it. You can do that yourself search the site and there are posts on how to do it. You don’t even need a meter, you can read it from the MFD.

    As far as the reader it’s Autel software talking to Toyota software. Doesn’t always jive 100%. The basic emissions codes do by law but your codes are not emissions codes. Some of them at least. Chapman pointed out a glaring error. Was adaptive cruse control even an option in 2008?
     
    #11 Skibob, Jun 18, 2019
    Last edited: Jun 18, 2019
  12. Skibob

    Skibob Senior Member

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    The newest one has a different part number than the first 3. Don’t know it off the top of my head but you can find it here.
     
  13. Geedis

    Geedis New Member

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    For anyone who finds this thread later, here's a clear YouTube video I discovered after reading Skibob's reply, which shows how to check the 12V Battery from the MFD (multi-function display):
     
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  14. Skibob

    Skibob Senior Member

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    There is another way to access that menu also. You press the display button then press 2 points on the screen several times in succession. Saves on turning the headlight switch. If you look around you can find the two points. It would be hard to verbally describe them.
     
  15. ChapmanF

    ChapmanF Senior Member

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    My guess involved some poor underpaid Autel employee trying to copy code definitions from some abbreviated cheat list found by google, seeing something about "acc leakage" and adaptive cruise was just the first thing that came to mind. Probably hadn't heard of a brake accumulator.

    When I use the voltage shown in the MFD signal check, I typically find it to be a bit more than half a volt lower than measurements elsewhere at the same time. It's fairly consistent with itself, so I use it often enough, but I tend to avoid drawing dire conclusions when comparing it to anybody else's "your battery is done for if it's below x" charts.
     
  16. Skibob

    Skibob Senior Member

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    True but it is something anyone can check themselves. 11.5v perhaps you investigate more, 10v and you pretty much know there is a problem. After that comes 2 groups of people. The chargers and the replacers. Toyota dealer always seems to say replace. As far as charging I would like to know how much the car is driven and time the car is in ready mode. 2-3 five minute trips a week won’t keep the charge up but if someone is driving 30 minutes or more 5 days a week my guess would be bad battery.
     
  17. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Can the car be driven in its current condition?
    If it can be driven, do you find that the brake actuator pump is running more than normal? (this pump sounds like a rattlesnake when the pump is running. Repeatedly press the brake pedal to force this pump to run while the Prius is READY, so you can identify when it is running.)

    If yes, that is an excellent indication that the brake actuator needs to be replaced and confirms that DTC C1256 and C1391 are correct.

    If that does not seem to be a problem, DTC C1300 means that the skid control ECU needs to be replaced. If the 12V battery is not weak, it could be that errors within the ECU are causing the other DTC logged by that unit.

    Besides that it appears that you need new TPMS sensors to be installed next time you buy tires, if not sooner.
     
    #17 Patrick Wong, Jun 19, 2019
    Last edited: Jun 19, 2019
  18. Geedis

    Geedis New Member

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    Thanks for this. YES, I have been noticing this for a long time; it's much more frequent than it used to be. But I had no idea what it was.

    Checked the battery today. Readouts were:

    Ready: 12.3
    IG ON: 11.7
    Car on: 14.3

    So, all things considered, it seems like the main issue is in fact the actuator.

    Next Key Question:
    Is there a reasonable way to determine whether the other codes are legitimate? For example, I see "Transmission Control: Fault." If this car has a transmission problem, it probably does not make sense to fix the actuator.
     
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I would not worry about the other fault codes besides the ones that relate to the TPMS system. The transmission control fault is just saying that ECU is aware of a hybrid system fault. The fault is that the braking system is impaired.
     
  20. Geedis

    Geedis New Member

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    Got it! Thank you.

    For the record, the quote I just received is:
    • $425 for used ABD control module with a 1 year warranty.
    • $275 for installing
    • $100 for programming -- says sometimes this has to be done through the dealer, which would be $200
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    • $800 to $900 total cost