brake/ABS module bleed issue

[deejayh]

in the final stages of getting my car back together - I had to manually walk back the e-brakes in the rear calipers due to low voltage from my battery dying while I wrapped my car - dont ask.

In taking those calipers off, I must've lost most of the brake fluid in the hard line. I successfully bled the rear passenger caliper, but can not get any fluid out of the line on the driver rear.

Took the caliper off and let the brake line hang, pressed brake pedal and it firmed up almost instantly. No fluid...

Went under the hood and cracked the rear driver abs module connection line, which I also found bone dry.

Is a solenoid stuck shut in the ABS module? I am thinking I need to pull the module and blow some alcohol through with some compressed air if i have a stuck valve.

No I dont have a vacuum pump but will go get one if that is the way to fix the issue.

Anyone have any solutions or ideas?

[SwankPeRFection]

You’re probably going to need to go through the ABS bleed procedure via VCDS if you ran any of the lines completely dry. Why did you disconnect the brake line from the caliper to simply deal with the parking brake retraction?

[deejayh]

Hey I said dont ask! my battery was low voltage and i didn't check before running the ebrake commands, so somehow things got really goofed up. I had to pull the calipers off to manually turn the rear side of the piston (where the e-brake engages) back all the way so the e-brake motor detected a "home" position. E-brake seems to work fine now - no codes.

ABS bleed procedure via VCDS wont let me hit the "go" button. I am reading channel 10 on the ABS Basic Settings and all the fields are green, but it wont let me hit the go button.

Wondering if I should pick up a vacuum filler and try to feed fluid into the caliper all the way back through the ABS module.

I am concerned I might have a stuck solenoid in the module though, so my current plan is to pull the ABS module off the car and see if I can get the valve working again. I do have a used ABS module (same PN) from a 2010 s4 that is on it's way to me, in case I can't resolve the issue. I hope I dont end up in a worse situation with air/solenoids stuck trying to swap in a new module

[SwankPeRFection]

If there’s any codes stored in the modules due to the ebrake back off procedure not completing, you’ve going to need to clear them and I would again, issue the commands a couple of times to put them in service mode and take them out. If that’s not working, then it’s quite possible that’s the root of your problem. The system may not be allowing the caliper to work in order not to damage the parking brake or cause other safety issues. This sounds like a “current state” issue and not necessarily a physical problem where something is broken higher up. If you didn’t have issues before and you ran into that ebrake service position problem, that’s should have been fixed properly first and from the sounds of it, you didn’t do that. They don’t require fully taking them apart to fix a mid-failure like that, but it does require some resets and interaction with the parking brake and VCDS to get them to respond again. It’s the same issue that happens if you try to back them off or put them back in service but you forgot to hook the plug back up on them. They’ll be in a state of unknown and then anything to do with ABS/traction control/ESP will be fucked up and not working due to the system not knowing what their current state is.

In super rare instances, where the system still doesn’t respond but physically you are absolutely sure the calipers are where they should be parking brake wise, a full voltage cut for several minutes may be required to fully clear and reset any current states the car thinks it’s in. You may need to pull battery for at least 10-15 min, then hook back up without stating the car and do a Gateway List poll and see what you have. Clear all codes and then power/accessory cycle the car and then do the service mode retract and back to normal position.

Also, FYI, bleeding on these cars, especially THOUGH the ABS module requires a pressure based brake bleeder on the master cylinder. You need a lot of pressure on there to bleed properly via the ABS bleed procedure. It’s possible it’s not initiating if it’s not seeing any (if you were doing the bs pedal pump bleed old school process), but definitely check the first part described above first.

[deejayh]

Thanks Swank - you are the man! such an asset to the audizine community!!!

just disconnected battery - going to wait 15-20min and VCDS the e-brake open/close to make sure everything is working properly.

Will report back if that doesn't work - will run and get pressure bleeder today and try that.

[deejayh]

OK - just verified the parking brake is working properly - cycled open/closed 2x and did a function test. Everything is good in the p brake module.

Just tried to run the abs partial bleed group 10 in basic settings and got this:
Saturday,10,February,2024,11:31:42:08883
VCDS Version: Release 23.11.0 Running on Windows 10 x64
www.Ross-Tech.com

Address 03: ABS Brakes Labels: 8K0-907-379-V1.CLB
Control Module Part Number: 8K0 907 379 CA HW: 8K0 907 379 CA
Component and/or Version: ESP8 quattro H04 0030
Software Coding: 280D1A
Work Shop Code: WSC 06325 000 00000
VCID: 7AAEF8607CDD72EA617-802E
2 Faults Found:

01486 - System Function Test Activated
000 - -
Freeze Frame:
Fault Status: 01100000
Fault Priority: 4
Fault Frequency: 1
Reset counter: 159
Mileage: 244164 km
Time Indication: 0
Date: 2009.06.26
Time: 00:06:49

Freeze Frame:
Hex Value: 0x0000
Hex Value: 0x0722
Hex Value: 0x0031
Hex Value: 0x3196
Hex Value: 0x00FF

00473 - Control Module for Elect. Park/Hand Brake (J540)
013 - Check DTC Memory - Intermittent
Freeze Frame:
Fault Status: 00101101
Fault Priority: 6
Fault Frequency: 1
Reset counter: 199
Mileage: 244164 km
Time Indication: 0
Date: 2009.06.26
Time: 00:08:47

Freeze Frame:
Hex Value: 0x0000
Hex Value: 0x02A2
Hex Value: 0x0032
Hex Value: 0x0295
Hex Value: 0x00FF

[deejayh]

I went through the sequential output test for ABS. Ran through all the steps without fault. Rear driver sequential test i didn't feel the vibration in brake pedal like i did for the other corners. wondering if this is because the line is dry, or if it's due to the e-brake motor not working properly. I dont have any codes in e brake module now - that intermittent one did not come back, and the only code I get on ABS is this:

Saturday,10,February,2024,12:43:32:08883
VCDS Version: Release 23.11.0 Running on Windows 10 x64
www.Ross-Tech.com

Address 03: ABS Brakes Labels: 8K0-907-379-V1.clb
Control Module Part Number: 8K0 907 379 CA HW: 8K0 907 379 CA
Component and/or Version: ESP8 quattro H04 0030
Software Coding: 280D1A
Work Shop Code: WSC 06325 000 00000
VCID: 7AAEF8607CDD72EA617-802E
1 Fault Found:

01486 - System Function Test Activated
000 - -
Freeze Frame:
Fault Status: 01100000
Fault Priority: 4
Fault Frequency: 1
Reset counter: 159
Mileage: 0 km
Time Indication: 0

Freeze Frame:
Hex Value: 0x0000
Hex Value: 0x0702
Hex Value: 0x0031
Hex Value: 0x3193
Hex Value: 0x00FF



Any ideas? the brake pedal is still super firm when I crack the driver rear caliper bleed screw. No fluid coming out

[deejayh]

couldn't resist cracking the abs module line to the driver rear caliper - I found brake fluid!!! was bone dry before - do I need to be patient and cycle the pump a bunch?

[deejayh]

If there’s any codes stored in the modules due to the ebrake back off procedure not completing, you’ve going to need to clear them and I would again, issue the commands a couple of times to put them in service mode and take them out. If that’s not working, then it’s quite possible that’s the root of your problem. The system may not be allowing the caliper to work in order not to damage the parking brake or cause other safety issues. This sounds like a “current state” issue and not necessarily a physical problem where something is broken higher up. If you didn’t have issues before and you ran into that ebrake service position problem, that’s should have been fixed properly first and from the sounds of it, you didn’t do that. They don’t require fully taking them apart to fix a mid-failure like that, but it does require some resets and interaction with the parking brake and VCDS to get them to respond again. It’s the same issue that happens if you try to back them off or put them back in service but you forgot to hook the plug back up on them. They’ll be in a state of unknown and then anything to do with ABS/traction control/ESP will be fucked up and not working due to the system not knowing what their current state is.

In super rare instances, where the system still doesn’t respond but physically you are absolutely sure the calipers are where they should be parking brake wise, a full voltage cut for several minutes may be required to fully clear and reset any current states the car thinks it’s in. You may need to pull battery for at least 10-15 min, then hook back up without stating the car and do a Gateway List poll and see what you have. Clear all codes and then power/accessory cycle the car and then do the service mode retract and back to normal position.

Also, FYI, bleeding on these cars, especially THOUGH the ABS module requires a pressure based brake bleeder on the master cylinder. You need a lot of pressure on there to bleed properly via the ABS bleed procedure. It’s possible it’s not initiating if it’s not seeing any (if you were doing the bs pedal pump bleed old school process), but definitely check the first part described above first.

maybe the smart move is to go get pressure bleeder tool and bleed the ABS module via manual

[SwankPeRFection]

You have to do a not a bleed on that line with pressure on the system on the master. Brake stiffness won’t go away unless you start the car for a few seconds at least. The ABS module test error is because it needs to cycle through the drive cycle for ABS and stability control. This is don’t once the car is operational and you basically drive around at slow speed 5-15 MPH straight and then in a circle both ways (left and right) and eventually it passes that test and it’s done and clears.

Focus on bleeding that line. FYI, when I had issues with mine on the same side is was due to a bad brake line from the hard line to the caliper. I replaced all of them with braided ones and was able to bleed without issue. Not saying that’s what it is for you, but if you can get fluid to come out at the hard line connection at that corner but not through the rubber brake line, then it’s that line.

[deejayh]

You have to do a not a bleed on that line with pressure on the system on the master. Brake stiffness won’t go away unless you start the car for a few seconds at least. The ABS module test error is because it needs to cycle through the drive cycle for ABS and stability control. This is don’t once the car is operational and you basically drive around at slow speed 5-15 MPH straight and then in a circle both ways (left and right) and eventually it passes that test and it’s done and clears.

Focus on bleeding that line. FYI, when I had issues with mine on the same side is was due to a bad brake line from the hard line to the caliper. I replaced all of them with braided ones and was able to bleed without issue. Not saying that’s what it is for you, but if you can get fluid to come out at the hard line connection at that corner but not through the rubber brake line, then it’s that line.

OK I still can't get fluid to come out of the hard line. I ran the ABS pump a few times and cycled through each wheel after removing the ABS module and cleaning it out. I am completely stuck. Pedal is now super soft, and will need to pretty much start over with the bleed, still no fluid coming through the driver rear caliper.

[SwankPeRFection]

Do you have a pressure bleeder on the master cylinder? If not, you’re wasting your time. You CANNOT do the ABS bleed without that setup. You have to maintain a certain amount of pressure on the system to do it right. I have never see a single version of the write up on the factory procedure for doing this that didn’t entail a pressure bleeder being used.

[SwankPeRFection]

Also, you cannot expect anything to build up in the hard line if it’s disconnected. All you’re doing is sucking air back up into it. Put the brake line back on the caliper and pressure bleed the entire system per the correct writeups and then worry about the ABS module (if there’s air in it).

[deejayh]

well I bled via pressure bleeder and still didn't get fluid out of driver rear caliper - swapped the valve body on the abs module and got fluid!!! success!!!