PRE-COLLISION SYSTEM UNAVAILABLE

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by PriusRos, Aug 28, 2017.

  1. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    Thanks for the description of the codes. But I'm not sure what it means when you say that the DTCs from the radar assembly were not recorded. I didn't understand the original printout either- What does YES or NO in the FFD column mean? Does YES mean error or no error? Also, as you noted, they were all marked as History. So did the printout tell you anything useful?

    I hope it is just the battery, but the airport is 30 miles from my house. Wouldn't that drive alone be enough to recharge it? I've also driven it every day since I got back on the 20th.
     
    #21 PriusRos, Sep 1, 2017
    Last edited: Sep 1, 2017
  2. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    If it isn't due to a low battery and the sensor is actually malfunctioning because of external damage, I still don't understand how or when the damage could have occurred. Husband insists that nothing happened between here and the airport. It was definitely parked in the driveway the whole time I was away (and he always parks face forward unless there's a need to back in to load luggage or something) and the chance of something hitting horizontally across the nose is next to zero.

    My only theory is that something happened before that I didn't know about, such as a shopping cart running into it in a parking lot, or the body or paint shop messing it up when I was having it worked on last year for hail damage (they messed up my interior headliner, broke a window, and the paint job doesn't exactly match - another long story) but the sensor was okay at first but got dislodged after being driven for a while. Think that might it?
     
    #22 PriusRos, Sep 1, 2017
    Last edited: Sep 1, 2017
  3. Elektroingenieur

    Elektroingenieur Senior Member

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    You’re welcome.
    Like all modern cars, a Prius has several computers, called electronic control units (ECUs), each designed to perform certain functions. The radar sensor assembly is one such ECU. When a technician uses the Health Check feature of the Toyota Techstream diagnostic system to produce a report like the one you shared, Techstream communicates with each ECU in the car and asks it to report the DTCs recorded in its memory.

    None of the DTCs listed in your report came from radar sensor assembly itself. This may be significant: if the radar sensor assembly’s self-monitoring feature had detected that it was malfunctioning or misaligned, it probably would have recorded DTCs C1A10, C1A11, or C1A14, none of which are in the report.
    Two ECUs, the forward recognition camera (LKA/LDA and Front Recognition Camera in the report), and the driving support ECU assembly (Pre-Collision 2 in the report), recorded DTC U0235, meaning they were unable to communicate with the radar sensor assembly. These are history DTCs, indicated by an X in the Hist column, so the communication problem occurred some time in the past, but the report doesn’t tell us when or how often.

    During the Health Check, Techstream was able to communicate with the radar sensor assembly, since it was able to retrieve the Calibration ID from it. This is the software version code, 8821F4702000, shown in the Calibration column, in the row for the “Front Radar Sensor” system. This proves that the radar sensor assembly wasn’t disconnected or completely dead.
    FFD stands for freeze frame data. When ECUs record a DTC, they might also store some additional information about what was happening at the time; these snapshots can be useful for diagnosis. YES in the FFD column means that Freeze Frame Data were available from the ECU when the Health Check report was run.
    The battery voltage was probably fine immediately after the car was parked. Remember that the auxiliary battery is always discharging, though, even when the car is off, since the ECUs and other components continue to draw current, called the parasitic load. If there weren’t any aftermarket accessories or other unusual conditions, I wouldn’t expect the battery voltage to have dropped enough after 12 days to cause trouble, but it is one possible explanation when there are several seemingly-unrelated electronic problems.

    If the car has been in a body shop, it’s also possible that the DTCs are from that work. Toyota asks body shops to check for and clear DTCs (PDF), but if the shop that repaired your car was as clueless as you describe, they may not have followed this recommendation.
    It’s possible. I think you’re unlikely to get a warranty repair for the radar sensor assembly with any nearby damage, no matter how it was caused, or if the car has a history of body repairs.
    If you’ve tried waiting, then it’s time for proper diagnosis and repair to restore the pre-collision system, an important safety feature.

    The first problem is the history of communication failures (U0235). If the DTCs weren’t cleared after the Health Check, the dealer should do this and road test the car. If U0235 or any other DTC returns, then they should follow the diagnostic procedures in the Repair Manual, starting with checks for CAN bus or wiring problems.

    If the radar sensor assembly is loose, there’s no sense adjusting it if it will drift out of alignment later. Hopefully this can be fixed just by tightening bolts or screws or by replacing the bracket (88201-60010, list price $12.35), not the entire assembly (88210-07010 or 88210-47090, list price $791.20).

    The next step would be to do the millimeter wave radar sensor assembly adjustment procedure, which the dealer called “calibration.” If the adjustment is successful, the problem should be fixed; if not, the radar sensor assembly may have to be replaced.

    Some tips for negotiating for the repairs:
    • Ask that you’ll only be charged once for the adjustment procedure, even if it fails the first time and they have to stop and replace the radar sensor assembly and adjust the new one, too.
    • If you’re paying for the work, it could be done at an independent shop, if they have the necessary tools and knowledge. If you call any shops, ask if they have the “Reflector C special service tool needed to adjust the radar cruise control on a Toyota”—I’d be surprised if anyone other than a dealer says they do, but if so, it’s a very good sign they could do the job.
    • If you have to buy a new radar sensor assembly, they are available from Japanese exporters (¥39,100, no U.S. warranty) and from dealers selling online ($540 or so from one near me) for much less than the list price—though it’s also reasonable for a dealer or shop to insist on furnishing the parts if they are to make a warranty for the repair. Nothing says they can’t give you a discount, though.
     
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  4. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    Elektroingenie, thank you so much for your detailed response.

    Guess what? Today, the message didn't come on! The only differences today are: first I wiped off the emblem with a paper towel, then was going to wipe of the windshield where the other sensors are located but couldn't reach. But it was raining, and the windshield wipers came on anyway. I don't know whether the wiping fixed it, the "loose" sensor had settled back into position after being driven for a while, or what.

    I don't know what it means and I expect it will come back on sooner or later. All I know is that the "damage" was not caused by a recent hit because the message wasn't there before. If the message returns, I'll ask them to start by tightening it, as you suggested.

    The second shop told me they wouldn't charge for the first calibration if the sensor has to be replaced. However, they wouldn't give me an estimate for the sensor because they said it all depends on what part is failing. So since I have a quote for the calibration but not for the sensor assembly, if it has to be replaced, it would be difficult to compare prices from an independent shop.
     
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  5. bestmapman

    bestmapman 04, 07 ,08, 09, 10 and 16 Pri

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    Hmmm, Glad to hear it. Mine did the same thing. It might be operating time instead of total days for a reset. It has happened to me 3 times I think, and each time it "reset" after a while.
     
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  6. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    I drove my car about 11 days since I first saw the message, for a total of 150+ miles, before the message turned itself off. I suspect that the sensor, if it is loose, as the dealer claimed, settled back into operating position and is therefore likely to become dislodged again. How long/how many miles did it take yours to reset each time it happened?
     
  7. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    I'm glad I didn't just fork over the $350 to get it re-calibrated. Now I know that it can reset all by itself, next time it happens I'll can at least tell them to start by tightening up the housing. But how much would that cost? I'm assuming they would have to open up the front of the car, which in itself usually costs a bunch.
     
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  8. bestmapman

    bestmapman 04, 07 ,08, 09, 10 and 16 Pri

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    Next time it happens to me, I will record miles and run time until the reset to see if there is any correlation.
     
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  9. ETP

    ETP 2019Prius(Limited),Highlander HYB Plat,B52-D,G,F,H

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    It's the squirrel in your picture. He likes the wires in your car.
    I had a "sensor dirty" message one day and the radar cruise would not work. It eventually went away.
     
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  10. dziadek1818

    dziadek1818 Junior Member

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    I have the same problem now :/
    no damage, but massages appear - precollision, LDA and DCC are unavailable.

    OBD shows C1AA9 code.
    did you check your with any scanner?

    Hope it can goes off as in yours
     
    #30 dziadek1818, Mar 19, 2018
    Last edited: Mar 19, 2018
  11. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    Well, the message has remained off since it went off last September, so I hope yours goes off by itself too. I posted a printout of the diagnostic codes I got from the shop earlier.
     
  12. dziadek1818

    dziadek1818 Junior Member

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    thanks for reply.
    I can see mine code is different than yours but in overall you had 10 diagnostic codes (DTC)?

    so, you just did nothing apart from this whipe you mentioned earlier and it just went off? :)
     
  13. Elektroingenieur

    Elektroingenieur Senior Member

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    DTC C1AA9 (Front Camera Module Beam Axis Not Adjusted) means there is a problem with the forward recognition camera; it’s unrelated to the millimeter wave radar, except that both are sensors used by TSS-P.

    Specifically, the Repair Manual (available by subscription to techinfo.toyota.com or toyota-tech.eu) says DTC C1AA9 is stored when “2 seconds after the power switch is turned on (IG), the forward recognition camera detects that Forward Recognition Camera Learning has not been completed.”

    The Repair Manual says to do the forward recognition camera learning procedure (about which I’ve written before, on April 29, April 30, and September 21), and if that doesn’t work, to replace the camera, and then to do the learning procedure with the new camera. I don’t think the code is likely to go away on its own.
     
  14. alanclarkeau

    alanclarkeau Senior Member

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    If it's under warranty, it should be covered.
     
  15. dziadek1818

    dziadek1818 Junior Member

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    This is just great!
    The car is out of warranty now thats why i am looking for own solutiona. Much appreciate contribution!
    We talking about front camera that is in the whindshield?
    I have tss-p package. Three things are unavailable - LDA, DCC and Precollision.

    What might be the reason for this? I know this is quite open question, but there was a time a month ago that front bumper needed to be taken off. Can it be that somehow guys at shop moved it or touched?

    Calibration now might be solution.
     
  16. James F Hooper

    James F Hooper New Member

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    Well, I have a variant. Someone stole the Toyota logo from my Prius - God knows why, they just pried it out. Toyota said I should pay $500 to replace the radar unit - seemed a bit much. Especially since when I bought this car, I declined the multi thousand dollar PCS system, and didn't pay for it. But with the logo gone, guess what was behind it? A radar unit!
    I bought a new logo (Also called the grill garnish some places) from ebay for $20. But it didn't have the tabs that fit my car, even tho it was supposed to fit my VIN #. so I broke off the tabs and glued the logo in place. Worked fine for 2 months, now the PCS light is on. Didn't come on when logo was taken, or when I replaced it.
    Any thoughts on where to go? Just learning that replace is first option before calibration gives me some leverage.
     
  17. Tideland Prius

    Tideland Prius Moderator of the North
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    Pre-Collision is standard on all 2017 Prius models as part of the TSS-P safety suite. (so all 2017 models will have a radar)
     
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  18. Elektroingenieur

    Elektroingenieur Senior Member

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    I’d suggest checking for DTCs using a Toyota Techstream diagnostic system or equivalent. If a warning light is on, there should be one or more codes, for which you can then follow the Repair Manual troubleshooting procedures. Without this information, repairing the pre-collision system is an expensive guessing game. Indeed, the trouble this time might not be with the millimeter wave radar unit at all.
     
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  19. Beachbummm

    Beachbummm Senior Member

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    rent one for the weekend and take the parts you want... put your defective ones on the rental.. if they didnt see it you didnt do it.. ... now ive never done this myself but I did see it in a movie once.
     
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  20. ETP

    ETP 2019Prius(Limited),Highlander HYB Plat,B52-D,G,F,H

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    Moved to a new house recently and it auto stops at the flowers near the drive way when backing up. My wife is happy.

    That squirrel is getting fat on your Prius wires.
     
    #40 ETP, Jun 18, 2018
    Last edited by a moderator: Jun 18, 2018
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