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    Eric Bruni New Member

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    Ok so long story short I had someone who claimed they could replace the front brake pads and rotors on my Prius, however apparently he couldnt because shortly after all of the above mentioned lights came on and I lost ABS in my car. In a panic I took my car to a near by shop who was able to pull the codes and reset them. The codes are as followed:

    C0200 = Right Front Wheel Speed Sensor Faulty
    C0205 = Left Front Wheel Speed Sensor Faulty
    C1300 = Fault inside ECU - Skid Control ECU Malfunction
    C1342 = Fault in Hydraulic System (FL) Front Left

    Car was back to normal until the next morning when the same thing happened again. I guess the question I have is does anyone know what could be wrong? In talking with the guy who reset the codes, from what I understand you need to disengage the ABS sensor before replacing the brakes, and I dont think that was done.

    Is this a easy fix or something much more expensive? Can you damage your ECU from a brake job? I appreciate in advance for any help or advice. Basically Im sitting here paranoid that this guy may have caused major damage to my car because he did something wrong during the brake replacement.
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    Eric Bruni New Member

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    nh7o Off grid since 1980

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    I can offer what I see in other posts here. One possibility is that the wheel speed sensors are unplugged, or not fully seated in their proper positions. Yes, it is important to disable the ABS by unplugging the relays, or by disconnecting the 12V system. Moving the pistons without doing that can trigger DTC's, but I don't believe that there would be any way to harm the ECU by doing this. Also, a sagging 12V battery can cause ABS issues, so make sure your 12V is good. The Prius brake system is complex, and requires Techstream to completely sort it out. More info here:

    100K maint - 1
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    Britprius Senior Member

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    It is possible that when the pads and rotors were replaced the mechanic did not disconnect the 12v battery, "this is a minimum requirement with the Prius when carrying out brake work," this can easily cause one or both of the caliper pistons to be pushed out by the electric hydraulic pump.

    If this happened (you need to ask) the brakes need to be bled by either a Toyota agent or someone with the know how and computer equipment. This will through the C1342 code. The brakes cannot be bled by normal means.

    It is not required to remove or disconnect speed sensors when doing rotor and pad change but your mechanic may have disconnected them or damaged the cables to them, inspection will tell.

    It is unlikely the ECU will have been damaged.

    At 5 years old we do not know the millage I would have the brake fluid changed if indeed the brakes need to be bled. The only extra cost should be the extra fluid used as Toyota recommend a fluid change when brake work is carried out.

    Hope this helps.

    John.
    Last edited by Britprius, Aug 26, 2012
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    Eric Bruni New Member

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    Thanks for the responses guys, the milage is aprox 106k, and I know that the mechanic didnt disconnect the battery. And when I took it to the shop the second time he did hook it up to a computer to bleed the breaks but I dont know if it was the right one i guess. Only thing I can imagine is that if the guy knew that it needed to be hooked up to the computer to bleed the breaks and reset the codes that it was the right one... Which is a good and bad thing, good because it was done right but bad because it didnt fix the problem for long.

    My thing is that the tech took the car for a test drive after and even I drove it for a good 30 miles the next morning before the christmas lights started again and I lost ABS. Im far from a mechanic but if it was a speed sensor or something like that, is it normal that I would be able to drive that far before it started up again?

    On the bright side Its good to know that its unlikely that the ECU was damaged. I just find it hard to believe that my battery went bad the exact moment my brakes went bad so Im hoping that its just the speed sensors. I called a Toyota dealer today because mine is still closed until monday, and thats what they thought it might be as well. Any additional responses based on this extra info would be great.

    Thanks again!
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    Britprius Senior Member

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    Was the door or the hatch left open while the work was being done or the radio left on as this would discharge a battery that may have already been in a poor state. I am not entirely convinced it is the 12v battery but this does cause some strange things to happen on the Prius when it gives up.

    Sorry I cannot be more precise, and please let us know the final outcome as this helps everyone with the pool of knowledge.
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    Eric Bruni New Member

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    No the car was off and the doors locked and closed. Like a dumbass I had a mechanic do the work on the side so its not like I dropped the car off at the shop and they could have done something like that.
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    Britprius Senior Member

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    Nothing dumb about trying to save some cash but unfortunately for you it did not work this time. The Prius brakes look like those on any other car but there the similarity ends. They are not difficult to work on provided the battery has been disconnected also there are two light blue relays in the fuse box that should also be removed. I do not know why the abs sensors have been affected as they are on the inside of the hub well away from the rotors and pads.

    I wish you well and hope it does not cost to much to put back in working order.

    John.
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    Eric Bruni New Member

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    Ok guys thanks for all the help, got everything taken care of so I figured Id update anyone still interested in the problem. From what I can tell the original problem was air in the brake lines that caused the lights to come on in the first place. And apparently the second time around the issue was much simpler. Low brake fluid (Only code that came up); caused by a leak on one of my rear brakes. I guess when the second tech did a check the first time he loosened and tightened the rear brake lines and due to dirt/rust when he tightened it back, it didnt get a good seal which caused the fluid to get low because of a small leak. Also the bleeding of the brakes the first time used up some of the fluid.

    I had them clean and adjust my rear brakes and Im back to normal. Thanks again and hope this can be of use to someone down the road.
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    graham hendren Geeman .. taximan

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    so what was the end cost? did it go back to toyota?
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    Helio Member

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    I'm having the same warning lights: parking brake, brakes, ABS, and VSC on my 2007 with 103K miles but haven't even touched the brakes. I was changing out the Denso Iridium spark plugs for the NGK Iridium IX and don't remember any warnings there. Then I moved on to the ICE coolant; dumped it and refilled with distilled water to begin a flush process, that's when the codes started. After a couple times of engaging the thermos pump to get all the air out (yes, it threw a couple codes that self corrected) I started getting rhythmically flashing brake warning lights. By the time I had done a flush three times, filled with coolant, and ensured the system was air free the lights were on permanently. I went for a test drive and could tell a big difference in brakes. The braking system is not regenerating the HV battery (no little cars on the display and no motor whine when braking); are increasingly sensitive the slower one goes; and clamp fairly hard with minimal pressure at stop with an audible release when the brake is let off. That car has some incredible braking power! The only issue I've ever had with the brakes was there annoying ability to set off traction control and ABS when braking across a bump in the road, I now read this is a recall.
    The 12 V battery is reading 12.3-12.4 from the hidden screen and goes down to 12.1V with IG-ON. The headlights are a little dimmer with the car not in ready, but nothing I would expect out of the ordinary.
    Going to undo the 12V to see if I can clear the codes and get a better reading with a volt meter.

    Any ideas?
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    Helio Member

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    Battery reads 12.71 V with the voltmeter and it did not clear the lights. I reckon I'm at the mercy of the dealer.
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    vskid3 Member

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    How long did you have the battery unhooked? It usually takes a few minutes for everything to clear, I usually do about 30 minutes to be sure. I would try clearing the codes with a scanner if you have access to one.
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    Helio Member

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    I had it unhooked for about 15. I'll try again Saturday. Strangely, the scanner isn't pulling any codes. I can see "readiness codes" that were generated when the car couldn't find coolant (I did not run the car without coolant, just activated the thermos pump) and some emission codes but those don't sit where the active codes are and can only be found in the "enhanced code" section. Also don't see any codes in the "hidden screen." I did run the "clear DTC" option several times but since there really weren't any it hasn't helped.

    Thanks!
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    Patrick Wong DIY Enthusiast

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    My first idea is that skid control ECU DTC will not clear when you disconnect the 12V battery. You have to follow a procedure that involves using a jumper on pins 4 and 13 of the OBD-II diagnostic connector, there are several posts here that describe how to do that. Further, a generic OBD-II scanner will not read the skid control ECU DTC.

    My second idea: Is it possible that you drained the inverter coolant in error and that an overheating inverter is causing the skid control ECU warning lights to come on?

    My third idea is that it is not a good idea to flush the engine coolant with water unless you actually saw significant rust or other deposits in the drained engine coolant, since the capacity of the system is ~9 US quarts but not more than around 6 US quarts will come out when you drain. The coolant heat recovery canister alone will store around 3 quarts.

    Since Toyota SLLC is already premixed 50% with distilled water, you'll end up with a lower % of coolant in the system if it already contains some distilled water prior to your adding coolant.
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    Helio Member

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    Thanks Patrick!

    The inverter coolant was changed two weeks ago and went very smooth; I found it far less work than the ICE coolant change! You're right, it was overkill to flush like that but I tend to be meticulous and an overengineer; I did find a few tiny pieces of what appeared to be calcium deposits but were cleared after the flushes. I already had full strength Toyota Red from when my coolant valve threw a P1121 so I went with what I had and measured the residual (9 qts. - the coolant dump) and calculated how to mix and achieve a final 50/50 solution. With the ICE coolant dump, I found that applying slight air pressure, with an upper limit of 3-5 PSI, through the radiator fill cap with only the thermos stopcock open will dump all but about 1.5 quarts. In retrospect I would not do that again, the thermos pump is somewhat difficult to get air out of and I do not want to damage the pump. The only obvious link with the alarms are the ICE coolant change and the spark plug change; those are the only two maintenance tasks I performed on that day. Two weeks prior was the inverter coolant change, oil change, air filter, MAF cleaned (used MAF cleaner); throttle body, intake manifold and valves cleaned (Sea Foam Spray and Cleaner).
    Additionally the tires were changed about 6,000 miles ago to Michelin MXV4 P205/65 (same size as the previous Goodyear's) and the dealer performed the recall on the steering shaft and...shoot, can't remember the other recall. I have not taken it in for the brake recall which this car had that issue; whenever the brakes are applied and I hit a bump or pothole it felt like I the brakes released and the traction control would initiate and you would hear the hydraulic pump activate.

    I appreciate everyone's input; hopefully we can narrow this down to a process and others can benefit.

    Thanks again! I will post as questions are asked or I get new info.
    Last edited by Helio, Aug 8, 2013
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    Helio Member

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    Adding some additional info:

    It is possible I drained the 12V battery below an acceptable level as I used the maintenance mode to cool the coolant down in-between flushes. This process involved running the heater on high with the car in maintenance mode for about 20-25 minutes until the coolant registered 110 degrees F. The car would have charged the battery again during the flush circulation while I forced the ICE to run until the coolant temp. would reach 180. I repeated this process 3 times for the coolant and once to cool the ICE enough to comfortably change the plugs.
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    Helio Member

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    SKID ECU reset per pins 4 & 13, Ready mode, press brakes 8 Xs in 5 seconds cleared the !, ABS, VSC lights for about 3 seconds; the "BRAKE" light remained lit.
    Also attempted this in IG-ON mode.
    Checked ABS wires to brakes and all appear and feel ok.
    Flashing lights are in series:
    ! = 6, 6, 9, 5
    ABS = 4, 2
    VSC = 4, 5
    BRAKE = constant
    TPS = flashing
    Seatbelt driver = flashing
    Last edited by Helio, Aug 9, 2013
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    Patrick Wong DIY Enthusiast

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    I suggest that you seek professional assistance as your skid control ECU may have failed. You'll need to have your local Toyota dealer or competent independent pull the DTC and provide you a diagnosis.
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    Helio Member

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    I thought I might be heading down that road...
    Do you think it was something I could have done? I'm completely baffled why it coincidentally happened during the coolant change.

    Thanks for the assistance! I'll post what I find out next week.

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