My daughter's 2005 Prius recently developed an ABS issue. If anyone can provide any insight, I would be grateful. Details below. Car: 2005 Prius Miles: 77k Problem: Recently the above lights showed on the dashboard. There has been NO recent brake work, no recent accidents, no known reasons that I know of would have introduced air into the system. Dashboard lights(Note - VSC and "Slip Indicator Lights" are NOT lit.): 1 - BRAKE 2 - Brake System Warning light (Circle with parenthesis and exclamation point) 3 - ABS Note: If I clear the ABS code, it comes back only "when" I press the brake pedal the first time after clearing the code, but to be clear, not until I press the brake pedal. Codes (as read by "Kingbollen Ediag Elite"): C1344 Hydraulic System(RL) Indications: 1 - The brake reservoir is slightly over full. With the reservoir slight overfull, I wondered if some issue is pulling air into the system. 2 - With the reservoir slightly over full, it suggests there is no brake fluid leak… unless the system is sucking more air in than is leaking… but I have seen no leak indications. 3 - The reservoir level has come down slightly when I unsuccessfully tried to bleed the brakes, now it is maybe only 1/4" above full. 4 - When bleeding the rear brakes, a small amount would drain out the rear brakes, but I could not get the pump to actuate. I was using a "Kingbollen Ediag Elite" OBD2 Bluetooth scanner, which has ABS bleed capability, but maybe I was not using it correctly, or maybe this issue prevents the pump from operating. Other things checked: 1 - both rear wheels removed, and brakes inspected, no visible leaks, brake pads appear normal (suggesting no pads are dragging), everything looks perfectly fine. Diagnosis with "Kingbollen Ediag Elite" OBD2 Bluetooth scanner: --Wheel cylinder voltage diagrams 1 - Diagram 1 - At rest, brake pedal NOT pressed, both left and right rear wheel cylinder voltages look like this at 0.43 volts: 2 - Diagram 2 - With brake pedal pressed, the other 3 wheel cylinder voltages respond. Take note that both front brakes show about 2.8 volts. The RR(Right Rear) cylinder voltage rises to 1.3 volts, BUT… the RL (Rear Left) brake cylinder volts stays low at 0.43 volts. See orange arrow. 2 - Diagram 2 - With brake pedal pressed, the other 3 wheel cylinder voltages respond. Take note that both front brakes show about 2.8 volts. The RR(Right Rear) cylinder voltage rises to 1.3 volts, BUT… the RL (Rear Left) brake cylinder volts stays low at 0.43 volts. See orange arrow. 3 - Diagram 3 - Shows RR wheel cylinder voltage shows good fluctuations with brake pedal pressure when brakes are pumped several times: 4 - Diagram 4 - Shows RL wheel cylinder voltage DOES NOT fluctuate when brakes pressed, but merely shows a small "blip" in voltage, and stays low at 0.43 volts: I had posted earlier on another post named "Help Diagnosing Persistent BRAKE, ABS, VCS, and ((!)) Lights", and Tombukt2 had said " This is all actuator control and that lil pump looking thing on pass side firewall . I believe is rear brake pump or control.". I think Tombukt2 may be referring to the "Stroke Simulator". Thank you Tombukt2, I was not even much aware of that until you mentioned it. And Brian1954 said I should create a new thread, so that is why I have created this new, and more detailed, thread. Thank you Brian1954. Meanwhile I am trying to learn more about the system so I can narrow things down, and prove which component failed, before I start replacing things. Thank you all for your help, and patience reading this long post. Mdixon1
Generally at the end of the day you're you're generally doing actuator for a few months I was doing 4 a week . I never looked to see what that thing was on the firewall mine was making a racket at one point . Actuator replacement fixed all that
it might be helpful to get a prius aware code reader and get the actual trouble codes to begin the diagnosis
I had a car here that the rear brakes had been done. I believe this was the code after much looking and fussing around what I found was the brake shoe trailing on rt side was not in the slot on wheel cylinder . This caused the tab on shoe to dig into rubber boot of cylinder push in incorrectly and cause fluid loss round the boot saw it run inside of backing plate looked at cylinder saw issue immediately put tab in slot Wella..
The OP included the trouble code in post #1. "Codes (as read by "Kingbollen Ediag Elite"): C1344 Hydraulic System(RL)" Why would the OP need a different scanner? The screenshots in post #1 look like they are from the "Kingbollen Ediag Elite" that the OP used. It looks like a very capable scanner for the brake problem in his daughter's Prius.
Funny, both bisco and I missed it, tucked into the middle of that post there. I saw all the later data stream screenshots, and thought it seemed odd to post all that and not the code(s).
I am very sorry for the delay in responding. I am very grateful for your commentary, help and interest in this problem. Contributing to my delay is this… I was carefully writing all my responses in Microsoft word, responding to every comment, and just had not posted yet… and then when I looked tonight… the document is now gone. I have no idea what happened to it. So, starting again, more abbreviated this time. Tombukt2 said: "at the end of the day you're you're generally doing actuator" Agreed. I am still researching, studying the ABS system, just in case there is something than can be done, but yes, I am 99% resolved to changing it out. Bisco said: "this thread is interesting, especially post 13. brake-code-c1344-and-warning-lights.160013" Thank you, I intend to carefully read that thread. Tombukt2 said: "… I found was the brake shoe trailing on rt side was not in the slot on wheel cylinder…" I have inspected both sides, and didn’t see any leakage… both sides are very dry, and no recent brake work has been done. Brian1954, ChapmanF, bisco: <various commentary on the scanner> Thank you all for your guidance. Bisco said: "aren't there possible sub codes?" Yes, apparently there are advanced ABS codes. I scraped the internet and found a document with the following on the bottom of each page "2004 Prius – Preliminary Release (RM1075U)". I only have about 8 pages of that doc, but apparently it is called "Toyota Prius 2004 Service Repair Manual + Wiring Diagrams". On page 05–1079 of that document, I see this indicating there are indeed advanced codes: However, based on my indications, with the Rear Left brake "cylinder volts" not responding like the Rear Right cylinder volts, I think those advanced codes aren't going to tell me much. With those 5 advanced codes, they all look like it implies rebuilding (I am assuming rebuild kits are not available), or replacing the whole assembly... just like Tombukt2 initially suggested. Even if there are other advanced codes, my reader doesn’t show any of the advanced codes. I suppose that the is the advantage of paying hundreds/thousands for the professional level scanners. Meanwhile today, I did some more analysis with my scanner, and discovered another clue… when brake pedal pressure is applied the "Left rear solenoid current" stays low at 0.0 volts instead of responding like the right rear solenoid current. However, I don’t think this additional clue tells me much, as it still suggests a problem in the ABS control module on the ABS assembly… again supporting what Tombukt2 said regarding replacing the assembly. I have been hoping to discover a bad electrical connection, or some other issue, but that seems increasingly unlikely. At this point I am just trying to turn over every stone looking for clues before replacing the module. I suspect there is a failed electronic component inside the ABS control module, but without a circuit diagram of the control board, and more info to support it, I am still looking at replacement of the ABS assembly.
In gen 2, those are two different things: the brake ECU is inside the cabin under the dash, and the brake actuator is out on the firewall. So that "Left rear solenoid current" does need to pass through a wired connection between them. But pay close attention to the circumstances. After the ECU has reported a RL hydraulic pressure issue, it is likely to lock out power to that solenoid on purpose (to avoid, say, pumping all the brake fluid out in case a leak in that line was the problem), and so the reading staying at 0.0 would be as expected. It might be most interesting to see what happens there on the first pedal press after clearing—the one that causes the code to be logged again. It might happen quickly enough for datalogging to be the only way to see it. (Even datalogging by a scan tool depends on repeated polling over the multiplex network, so if anything happens so quickly it fits in one polling interval, even scan tool datalogging might not show it, and actual instruments inserted into the solenoid and pressure-sensor circuits might work better.)
Wow, that is extremely helpful information. It gives me more info to analyze with, thank you so much. My intent is to study the Toyota/Prius shop manual and gather whatever information I can on the theory of operation so I can narrow the issue down... and there is a big fear of doing a painful replacement and finding out it did not fix the problem. As always understanding the clues and their implications is important. Thank you ChapmanF.
