LS400_96

Hi,
I need some help with a ABS brake actuator replacement on a 2008 Lexus LS460 w/ 65k miles. I have had an issue with the ABS brake actuator for some time. I have been getting the brake and VSC Christmas lights with a host of codes (C1203, C1241, C1256, C1336, C1345, C1368, C1391, C1392). The car had a harsh brake symptom where it felt like it was on and off vs a gradual stop. The accumulator built up pressure and could hear the motor running when getting in the vehicle and starting. I had an instance where I did not have a charger on the battery when I was using Techstream to bleed/reset the brakes.

I purchased a used ABS brake actuator hearing lot of these go bad and replaced it over the weekend. The install went fairly well in the beginning except for a minor brake fluid leak in a couple of the brake lines which I am still pinpointing). I used the link below and had a charger on the battery this time and ran through the instructions using the link below to bleed brake/clear out the codes.

https://www.clublexus.com/forums/ls-...ssages-10.html

I was able to clear most of the codes except C1345 (Linear Solenoid Valve Offset Learning undone) and C1368 (Linear Solenoid Valve Offset). I tried numerous times with the charger on the battery. I zero down front and rear, bled brakes with actuator removed procedure, reset memory, linear valve offset. I am having issues with the Linear Solenoid Valve Offset where the ABS and brake warning lights are not blinking after completing. I still had the same lights on the dash so I drove the car around and it stopped more linearly and other than the lights seemed to be functioning correctly.

I tried clearing the two codes again C1345 and C1368 numerous times again. In one of the process of zero out the accumulator, I ran into a situation where the accumulator will not build pressure any more.

I do not hear the pump running and hear a beeping noise (low accumulator pressure) every time I get in the vehicle/turn the vehicle on. The brakes have a delay to braking when I start the vehicle and try to stop. The following are the codes I now see: C1253 (Pump Motor Relay), C1256 (Accumulator Low Pressure), C1345 (Linear Solenoid Valve Offset Learning undone) and C1368 (Linear Solenoid Valve Offset).

Can someone help with my issues? I am in the processing of reinstalling the old ABS brake actuator to see if I run into the same issue. I pulled apart the brake pump to see if the commutor and brushes are in good condition and don't see them having an issue. Any assistance would be greatly appreciated. Thank you.

swfla

iTrader: (1)

I see several possibilities. You point to a thread about the RX, LS may be different procedure. It's not clear to me you chose the correct procedure on Techstream. Used part may be defective. There may be more components in the brake system that are malfunctioning. I could be wrong about all the above but hope that giving it some thought will help you.

Boykie

If replacement unit is good, bleeding was done using 'actuator replaced' utility correctly following procedure - there should be no problem calibrating linear valve afterwards using according utility. Failure to calibrate offset indicates a failed unit 99% of times.

LS400_96

Thanks for the reply. I am contemplating whether the ABS, TRAC, VSC ecu may be bad as well causing the accumulator pump to not run??

LS400_96

Yes, that may be the case. I will replace with my original unit and see if I am able to get the accumulator pump to run again and have some driveability.

Boykie

I assume you have fsm. If not - get one. You need to verify everything is kosher - all connectors are attached etc, then attempt offset cal following fsm steps really carefully. Yes, you should have pump priming acc pressure before attempting cal. You said you have leaks? Offset cal procedure uses high pressure to pressurize all lines, all leaks should be eliminated prior, brake mechanics should be all good and car should be assembled and on wheels.
If offset cal fails after everything - it's a junk unit. Plenty of those in rotation, return it for a refund.

LS400_96

No, I do not have an FSM. Need to get one. Is there a section that I should be looking at for the offset cal procedure?

Boykie

Brake -> brake control -> brake actuator -> installation
brake -> brake control -> ecb system -> initialization, then calibration

LS400_96

Is there a specific condition where the accumulator pump would not run at all? Is there a relay or fuse potentially?

miket000

You can probe the 2 wires going directly to the motor. I pushed my probe leads through the insulation directly into the wire. With the car turned on they should be hot, 12v or so. In my case they had voltage, my motor was dead. I think that is the most direct way to check. If you plan on replacing it anyway making holes in the wires won't matter.

LS400_96

Copy, I will check the wires. I have the old ABS brake actuator installed now. Going to see if the accumulator pump is going to run. I have not put in any fluid as I am trying to see if the pump will run prior to filling the tank. I will keep you all posted. This will be a temporary fix until I can get a hold of another brake actuator.

LS400_96

Just plugged in the battery and opened the door and the car is beeping without the accumulator running.

miket000

..... deleted

yyymmm31

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Sorry to hear that your brake actuator replacement didn't go through. I experienced this situation once. I posted my experience/solution when dealing with this issue the link below:
Tutorial LS460: Clear “Brake Malfunction, Check VSC System” Dash Error Messages - Page 7 - ClubLexus - Lexus Forum Discussion
I am also attaching the Lexus Technical Service Bulletin for performing this procedure as a reference.
BTW, what VCI/OBD2 interface are you using? I tried several cheap Mini VCI J2534 simulated USB cables (about $25 each). I found that they could perform some basic Techstream functions but were often unreliable (lost communication, etc.) when performing more advanced functions such as programming TPMS sensors. Eventually, I settled with a VXDiag VCX NANO connector (about $80), which performed all the advanced Techstream functions that I needed to do. So, check your VCI/OBD2 interface and make sure that it can communicate with your car reliably and consistently.
Disclaimer: I am not a professional mechanic. I am just sharing my DIY experience of maintaining my LS460.
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LS400_96

Thanks for your inputs. I have tried your procedure without any luck. I ensured I had the battery charger on while performing the bleeding procedure. Even did a mock dry-run as you indicated without any luck. Now the accumulator pump is not running. The accumulator sensor voltage is 0.45V (it should be ~4.5V?). I feel like it may be a fuse and/or relay but cannot find any burnt. Something is not allowing the pump to run. I am using a VCI/OBD2 connector. May need to get a VXDiag cable but need to troubleshoot the pump issue prior.