Author Topic: Brake Test fail  (Read 17282 times)

Alexm1

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Brake Test fail
« on: July 17, 2013, 06:44:21 AM »
Hello, New user and first post so it could well be something I am doing. I have a 2003 K1200 GT.
Plugged the GS 911 in for the first time today, Engine section showed all was well, no stored errors.
ABS section showed some old stored errors but no faults present, cleared and all was well. Took the bike for a run and no errors appeared.
The problem: I performed a brake test on both the front and the rear brakes, red line appears and begins to move to the right across the screen, I can squeeze the lever or push  the pedal as hard as I like, it will not turn green.  After I cancel the rear brake test I get a message indicating no signal from the controller, no such message when I cancel the front test.
The brakes work perfectly, no dash lights, no fading that I have noticed.
I will have to bleed the wheel and control circuits to prove to my self that all is well but has anyone experienced this issue?
Appreciate any advice.
Alex.

UPDATE:
I think I like this GS 911!
I recorded a CSV log file whilst I was performing this test and have now had a chance to digest the results.
with the front brake off the control pressure is 19.7 and front wheel pressure is 18.7.
with the front brake on the control pressure is 31.6 and front wheel pressure is 56.99.

with the rear brake off the control pressure is 19.57 and rear wheel pressure is 17.32.
with the rear brake on the control pressure is 44.57 and rear wheel pressure is 44.51.

Through all of this the battery voltage varies between 10.04 and 10.86.

My guess is I have a faulty battery.
I keep the bike on a maintenance charger so would not notice a weak battery initially.

Can anyone with a little more experience with the GS 911 confirm my thinking? (or give me other readings to check)
Thanks

Alex.
« Last Edit: July 17, 2013, 07:46:25 AM by Alexm1 »
Alex

kobus

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Re: Brake Test fail
« Reply #1 on: July 17, 2013, 03:46:21 PM »
Alex, the Battery voltage can influence the pressure reading (and cause a lot of other problems). 10.x V is definitely too low (if it falls this low after being on a maintenance charger, I would also suspect the battery).

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bikecrazy5

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Re: Brake Test fail
« Reply #2 on: July 17, 2013, 09:15:05 PM »
agreed with Kobus the bikes with all the electronics bits and bobs do not like low voltages...one of the first things the ecu switches off when riding with a flat battery is the abs ,thus meaning you would only be riding with normal hydraulic brake pressure...

Alexm1

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Re: Brake Test fail
« Reply #3 on: July 18, 2013, 04:57:50 AM »
Thank you both for the feedback, good to get confirmation.
I did some more tests this morning and I appear to have a voltage drop between the battery and the ABS test point.
Voltage at battery 13.11 , ignition off.
Voltage as indicated by GS 911 viewing engine outputs 13.66 to 13.90. (Engine running)
Voltage as indicated by GS 911 viewing ABS outputs 10.8 to 10.9.(engine running)
I am assuming at this point that the ABS module connector has corroded terminals. I have yet to take it apart to see.
Anyone know where the battery voltage is sampled for the engine and for the ABS unit?
Note through all of this I have no error indicators, I would not be looking at this except the brake test failed on the GS 911. Great preventative maintenance.
Alex

kobus

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Re: Brake Test fail
« Reply #4 on: July 18, 2013, 11:16:31 AM »
Alex, there are a few voltages measured here.

1) The voltage on the battery terminal as sampled by the GS-911 ADC itself
2) The voltage as sampled by the engine controller ADC (somewhere on the ECU pc board) and reported to GS-911.
3) The voltage as sampled by the ABS controller ADC (somewhere on the ABS pc board) and reported to GS-911.

It's normal for these voltages to differ a bit (I would say up to 500mV would be OK) as there are scaling factors, calibrations and voltage drops involved.

If you have a decent volt meter with needle probe, measuring on the connector to the ABS would also be useful for analysis.

Please send an AutoScan of your bike so we know exactly what we are talking about here.

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... and then the company fleet.

Alexm1

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Re: Brake Test fail
« Reply #5 on: July 18, 2013, 11:35:15 AM »
Kobus, thanks for the response.
The battery voltage I referenced is taken with a fluke meter at the battery. The other two are taken from reports generated via the GS 911, one on the engine and the other on the ABS, CSV logs of each.
As indicated, no error codes, so I don't actually have a problem yet. I went for a ride today and all is well.
I plan to bleed both the wheel circuits and the control circuit this weekend and clean the electrical connections, with luck that will solve it.
I will post an update once complete.
Thanks again for the interest, much appreciated.
Alex

Roddos

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Re: Brake Test fail
« Reply #6 on: July 18, 2013, 11:42:56 AM »
Hi Alex

As you say this may be a "software feature" between the Gs911 and ABS ECU.

Would be helpful if others could check and report the voltage shown in the ABS ECU through their GS911
and report back  ;)


Alexm1

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Re: Brake Test fail
« Reply #7 on: July 19, 2013, 03:36:03 AM »
Just an update; reading the I BMW forum last night noticed that people commented on how hard they had to pull the brake lever (or push for the foot brake) to the extent that they felt the lever may break when performing the bleed test. So, armed with this new knowledge I re-did the test this morning; both front and rear turned green, front passed the test, rear would not get high enough pressure but did move well to the right on the graph.
It would seem that the voltage issue is a red herring. I will bleed the control and wheel circuits anyway and clean the connections that I can access. Will update further at that time.
« Last Edit: August 07, 2013, 01:26:49 PM by Alexm1 »
Alex

kobus

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Re: Brake Test fail
« Reply #8 on: July 19, 2013, 09:44:21 AM »
Yup, while implementing the bleed tests, I developed some serious forearm muscles. ;D
But this is on par with the official BMW tool.
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... and then the company fleet.

Alexm1

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Re: Brake Test fail
« Reply #9 on: August 07, 2013, 08:29:07 AM »
So, have completed a full brake service. Bled the front and rear wheel circuits and the front and rear control circuits. Everything works as it should.
While I was at the control module I removed and cleaned the electrical plug with CRC. (The contacts were clean before I started so it was not actually necessary.)
When I connect the gs911 and check the battery voltage on the engine tests it is just below 14 volts, engine running, when I check the battery voltage on the ABS tests it shows 11.1 volts or less, engine running.
I also redid the brake tests with the gs911, the front passes with no issues, (says adequately bled) the rear will turn green and the line moves into the second division but will not move all the way to the right, the report says insufficient pressure.
Following the tests I get an error code on the front and the rear indicating over pressure in the control module ( greater than 5.5 bar), I assume this is normal, it clears and does not come back so it is the tests that cause it.
Any one experienced the voltage issue or have thoughts on the rear brake not getting high enough pressure?
Alex

bikecrazy5

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Re: Brake Test fail
« Reply #10 on: August 07, 2013, 09:25:03 PM »
hi alex

is it only showing these faults on the brake test or in the autoscan

please post a auto scan so we can have a look.

regards
mike

Alexm1

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Re: Brake Test fail
« Reply #11 on: August 08, 2013, 03:25:19 AM »
Mike, thanks for the response. The faults show in the auto scan, I have attached two files. (one in the following note)
1/ auto scan before any tests, 2013-08-08 10.55
2/ auto scan following both tests, 2013-08-08 11.00. Both faults are present. Note that the front brakes passed the test, the rear brakes did not pass the test. On the graph both turned green and the graph moved to within 2mm of the third division. Cannot find how to attach a second attachment so will add an extra note with the second autoscan.
« Last Edit: August 08, 2013, 03:36:14 AM by Alexm1 »
Alex

Alexm1

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Re: Brake Test fail
« Reply #12 on: August 08, 2013, 03:33:15 AM »
second auto scan
Alex

bikecrazy5

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Re: Brake Test fail
« Reply #13 on: August 10, 2013, 09:51:43 PM »
hi alex
am I correct by assuming this is the servo assisted  abs unit[in other words makes a noise when applying brakes
have a look at the pressure valves they tend to get stuck with crud
http://forum.hexcode.co.za/forum/index.php/topic,4.msg177.html#msg177

Alexm1

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Re: Brake Test fail
« Reply #14 on: August 11, 2013, 07:15:23 AM »
Bikecrazy5, thanks. I had seen that post of jugheads but had not thought to link it with my symptoms. I will continue to pursue a fix but given that I do not have any error conditions other than when I bring them on with the bleed test I won't take the ABS unit out yet.
Yes it is the servo assist model, 2003 K1200GT.
My current plan is to find the source of the low voltage, I am just waiting for the circuit diagrams.
Thanks for your input, appreciated.
Alex