The bloody lights went on again. I had the issue before but intermittent, they come times to times and then go after restart. Now they are permanent. Code reader suggests those are brake pressure sensors located on master cylinder. Datagram show that there is about 20-30psi pressure even when pedal is not pressed (it used to be 0 previously). Seems have to replace both of them, at about £100 each... Booked to local garage for code read and advice...
Amber handbrake and DSC light.
- Thread starter ppavuk
- Start date
this morning I found them off. After driving 500 yards - on again. Hate those lights on instrument cluster! Ok, Monday will get this fixed!
Well, I certainly hate them when they aren't working as expected. When they were OK I was 100% fine with them
Did some research on the topic. This could be sensors (one or both) or ABS/DSC unit itself. Second option is way more expensive - new unit cost slightly less then 2 grands from BMW and needs to be coded to vehicle for extra 150 quid. Not something I am going to do with 12 years old car for sure.
So ordered two used sensors @30 quid pair to swap and see if any better. My idea is to connect sensors to the wire looms while not installing them to master cylinder. If motor tester will say there is 0 pressure I'll install them then. If tester will see pressure on not installed to master cylinder sensors - that would mean ABS unit is at fault. What I've done so far - I've swapped a loom from sensor 2 to 1 and from 1 to 2, and tester actually swapped pressure values as well. ABS unit know nothing is it sensor 1 or 2 (they are identical, same part number) - it all depends on wire, so seems ABS unit is able to read sensor values correctly and there is good chance that sensors itself are at blame. I also assume there is 0 pressure on master cylinder when brake pedal not applied - otherwise my wheels would be locked. At this time both sensors report pressure - one reads 5 psi - second 20 psi. What also I found - after certain time (about 20H) both sensors returns to normality, motor tester reports 0 pressure on both but once I press brake - they broken again. It seems to me they just stuck. I am pretty certain there is no pressure in master cylinder as no matter if ABS/DSC unit is dead or alive - pressure in master is applied straight to slaves, and wheel locks, which is not a case as car runs just OK. I'd feel if system brake at 30psi pressure while I am driving for sure!
I don't want to experiment with expensive brand new sensors so will try used for first go.
IF that won't work - will then take the whole thing to garage and shell out whatever money to get the bloody thing fixed. There is a company @Derbyshire which mastered to rebuild ABS/DSC units (mechanically and electronically) at about 250 quid. The culprit is that unit has to be sent to them which would mean car parked for a while. Though they can't test sensors as they aren't on ABS unit, but on master cylinder.
So worst forecast is 200 for brand new sensors + 250 for ABS unit rebuild + whatever garage will charge for labour.
What I know for sure - it is nothing to do with abs wheel sensors - they are fine on my car according both to code reader and my manual measurements with voltmeter. Other sensors like G-sensor and steering sensors does not report any failure too. Must be the bloody pressure sensors so I see good chance I'll get away with 30 quids and can of brake fluid.
So ordered two used sensors @30 quid pair to swap and see if any better. My idea is to connect sensors to the wire looms while not installing them to master cylinder. If motor tester will say there is 0 pressure I'll install them then. If tester will see pressure on not installed to master cylinder sensors - that would mean ABS unit is at fault. What I've done so far - I've swapped a loom from sensor 2 to 1 and from 1 to 2, and tester actually swapped pressure values as well. ABS unit know nothing is it sensor 1 or 2 (they are identical, same part number) - it all depends on wire, so seems ABS unit is able to read sensor values correctly and there is good chance that sensors itself are at blame. I also assume there is 0 pressure on master cylinder when brake pedal not applied - otherwise my wheels would be locked. At this time both sensors report pressure - one reads 5 psi - second 20 psi. What also I found - after certain time (about 20H) both sensors returns to normality, motor tester reports 0 pressure on both but once I press brake - they broken again. It seems to me they just stuck. I am pretty certain there is no pressure in master cylinder as no matter if ABS/DSC unit is dead or alive - pressure in master is applied straight to slaves, and wheel locks, which is not a case as car runs just OK. I'd feel if system brake at 30psi pressure while I am driving for sure!
I don't want to experiment with expensive brand new sensors so will try used for first go.
IF that won't work - will then take the whole thing to garage and shell out whatever money to get the bloody thing fixed. There is a company @Derbyshire which mastered to rebuild ABS/DSC units (mechanically and electronically) at about 250 quid. The culprit is that unit has to be sent to them which would mean car parked for a while. Though they can't test sensors as they aren't on ABS unit, but on master cylinder.
So worst forecast is 200 for brand new sensors + 250 for ABS unit rebuild + whatever garage will charge for labour.
What I know for sure - it is nothing to do with abs wheel sensors - they are fine on my car according both to code reader and my manual measurements with voltmeter. Other sensors like G-sensor and steering sensors does not report any failure too. Must be the bloody pressure sensors so I see good chance I'll get away with 30 quids and can of brake fluid.
Here's hoping you can get away with the cheaper option.
Tony.
Tony.
Thanks mate! I hope so too, though booked to local garage for proper code reading and overall diagnostic. Who knows what else bomb ticking in this car! I am actually not that concerned about bill rather about fact that I am not sure garage will go round same circles as myself but charge me for every hour of investigationHere's hoping you can get away with the cheaper option.
Tony.
Being software engineer myself I precisely know what is bug-fixing and I have no hope garage guys any better on bug-fix rather we, software guys, are. That's all simple if one had a problem before and know how-to-resolve-for-sure, but I am not convinced yet based on phone conversation with garage that they exactly know what is going on. I don't want to swap expensive parts until fixed - surely this is most expensive way.that's original Bmw part, there is no alternatives. Cheap as used. New ones 200 quid pair.
the sensors are straight on master, two small barrels with wires between brake lines. On different versions of abs there could be also setup when sensor is only one located on abs unit, but in my case two on master.
Of course lights went off yesterday, so I went to garage this morning with no evidence of issue. Had ABS error codes read and deleted at Clintons Garage in Kenilworth. On my way back lights went back. Another code read - pressure sensor 1 it is! So issue isolated then. Will wait for sensors to arrive and swap them both (I had sensor 2 recorded before as well so assume it may be not good too). At least scary error - "No connection to CAN bus" not manifestoing anymore, so most likely it is not ABS unit.
You need to eliminate the possibility that this could be the ABS module (black box bolted to the side of ABS pump) as they are a common fault and can show a variety of warnings / codes that are phantom. If I was you I would take it off (disconnect the electrical plug carefully then simply remove the 4 little bolts that hold it on). Then send it to BBA Reman in Kent and they will test it for you. They have a fast turnaround and if there is nothing wrong you just pay a £35 test fee and they send it back. If there is something wrong they will repair for you for just shy of £200 (but they waive the test fee) and I think they provide a lifetime warranty for as long as you own the car. The solder joints fail in these modules, my fault codes were showing a defective ABS pump but it was the module giving false readouts. Repaired, refitted and no more lights and codes.. happy days!!
Thanks for suggesting those guys!
I already done some research on this - there is number of companies offering same service, I've contacted few of them and they want full unit (electronics + pump) to be sent to them for testing. That would require a full system bleed after installed back - which is a hassle. For now I am waiting for replacement sensors, as they are cheap from e-bay and if this won't help - I'll send the unit out for rebuild for sure. I understand there is number of different ABS unit has been installed on Z4, some with internal pressure sensors, some with external, like my one. I know that for those with internal the only way is ABS unit rebuild, but for those with external sensors on master brake cylinder - sensors itself can be at fault. I still hoping this is not unit fault as errors I have read only suggest pressure sensors, not any other sensors, so I still hope to get away with cheap and fast fix. I have read tons of forums/blogposts on this and found that in case of ABS unit fault 3 lights come on - amber handbrake, amber DSC and amber ABS. In my case it is only two - handbrake and DSC. There is even a words "bifecta" and "trifecta" on bimmerfest.com to describe this common issues. So far it seems most of people with "bifecta" sorted issue by replacing pressure sensors.
Still waiting for replacement sensors, though made a bit more research. I do have a code scanner, pretty capable device - it can show the datastream. Normal value (no pressure applied) is -1.6 bar. I don't think this represent real pressure, but it what reads for good sensor. For sensor 1 pressure value can be anything at any time - in range of -1.6 (that's when bloody lights off) to +30. When I lightly knocked the sensor with a spanner - the pressure changes, and actually go to -1.6 after couple of hits. Although no changes on healthy sensor. So I think this must be as simple as sensor problem. It also seems to me I maybe will be able to replace it with no full bleeding, the sensor oriented slightly down off horizon, perhaps 30 degree or so, so if I quickly swap it maybe will be enough to depress brake pedal before finally tightening new sensor to get rid of any small air bubbles...
I'll update the tread once get the sensor replaced. Shame I've ordered it from e-bay, still to wait! I must be ordering it from amazon with next day delivery, but 80 quid difference though!
It also seems that sensor 2 has been replaced before - it seems to me a little cleaner, and different colour that sensor 1. Shame I don't have full service history.
I'll update the tread once get the sensor replaced. Shame I've ordered it from e-bay, still to wait! I must be ordering it from amazon with next day delivery, but 80 quid difference though!
It also seems that sensor 2 has been replaced before - it seems to me a little cleaner, and different colour that sensor 1. Shame I don't have full service history.
Seems fixed. Pressure sensor 1 it was. Since I replaced it - no more lights so far. I didn't had a big mileage since, but before swap lights went on every second time I start the car. Not anymore.
So, £49 for code read (I could avoid this, but my reader can't delete ABS codes for some reason) and £30 for pair of used sensors delivered. I've also managed to avoid full system bleed - I've just put sensor in place not tightening fully and depressed brake pedal. A little of fluid escaped - and I tightened the sensor. Pedal stiff and no bloody lights!
So, £49 for code read (I could avoid this, but my reader can't delete ABS codes for some reason) and £30 for pair of used sensors delivered. I've also managed to avoid full system bleed - I've just put sensor in place not tightening fully and depressed brake pedal. A little of fluid escaped - and I tightened the sensor. Pedal stiff and no bloody lights!
Today the second sensor packed up. Seems they die together Luckily I had another second-hand sensor so bolted it on the place in 5 minutes!
Luckily I had another second-hand sensor so bolted it on the place in 5 minutes!
if this continues read thread - asc/abs. if it is the module it is not as bad as you think.
Yeah, this could be module. Refurbished are on sale for pretty reasonable money. I am not excluding this is the module, but according to datastream likely sensors it is.
hope so, i brought my second hand unit for around £35, so either way its not that bad.
Does second-hand need to be coded to vehicle? Or it is just hydro part of the module?
yes needs recoding but there is a how to in the asc/abs thread.