ABS light stays on

[Finn]

Car has been working nicely the whole winter until I put the missing radio back on a week back. I had to remove the boost gauge for that and the gauge lamp caused a short to blow a fuse. It could be totally irrelevant for the problem at hand. Then this tuesday morning apparently the installed radio caused the old battery to die which I replaced for a new one. But after the battery replacement the ABS -system stopped working and the warning light stays on. A while back there was an occasion where the alternator and ABS -warning lights didn't go off but that problem had fixed itself the following morning. I checked the fuse beside the power block in drivers side strut but it was okay. I also measured the charging voltage which shows a healthy 14 volts.

[Steve Webb]

On its own I would have said a broken wire somewhere in the ABS system, but with all the other issues I would say you've blown a fuse somewhere. Maybe take a check of the relevant fuses in the main fuse box.
It sounds as though the radio / boost gauge lamp is causing problems.

[Suzumushi]

On its own I would have said a broken wire somewhere in the ABS system, but with all the other issues I would say you've blown a fuse somewhere. Maybe take a check of the relevant fuses in the main fuse box.
It sounds as though the radio / boost gauge lamp is causing problems.

Thee is another fuse, but to get there you have to remove some interior plastic parts



there is an relay with fuse on it, check these fuse, think this is the first thing to do.
because i also had some issues with ABS i found a dedra service manual for abs unit (4x4) but it's only in polish, so if You will not be able to sort this out i will try to translate it.
There is also service procedure in workshop manual that you can download from berlinasportivo site (these one in french). but it's in fench only, so not usable for me

regards

W

[Finn]

Thanks for the info guys.

Just checked the fuses which are all ok in the main and auxiliary fuseboxes. I also measured the resistances on the wheel sensors which are 1,5k in front and 1k at the back.

I can't find the test connector (T1) anywhere. I looked under the back seat and beside the strut near the abs hydraulic unit. Is there a diagnostics procedure where you earth pin 1 in the test connector and the ABS -light blinks to indicate where the problem might be?

[Suzumushi]

Thanks for the info guys.

Just checked the fuses which are all ok in the main and auxiliary fuseboxes. I also measured the resistances on the wheel sensors which are 1,5k in front and 1k at the back.

I can't find the test connector (T1) anywhere. I looked under the back seat and beside the strut near the abs hydraulic unit. Is there a diagnostics procedure where you earth pin 1 in the test connector and the ABS -light blinks to indicate where the problem might be?

Check the gaps:
gap between sensor and impulsator teeth on front wheel should be = 0.2-0.9mm
gap between sensor and impulsator teeth on rear wheel should be = 0.2-1.2mm

Check the impedance of sensors:
(for safety reasons disconnect battery)
Disconnect big connector from abs unit:
front left - pins 4 & 5 resistance = 900-2000 ohm
front right - pins 11 & 12 resistance = 900-2000 ohm
rear left - pins 7 & 9 resistance = 900-2000 ohm
rear right - pins 24 & 26 resistance = 900-2000 ohm

Checking voltages generated by sensors :
FL - pins 4 & 5 voltage min = 0.1V AC (turn Fl wheel)
FR - pins 11& 12 voltage min = 0.1V AC (turn FR wheel)
RL - pins 7 & 9 voltage min = 0.1V AC (turn RL wheel)
RR - pins 24 & 26 voltage min = 0.1V AC (turn RR wheel)

You can get more accurate readings when using osciloscope... if You have

Measuring voltage and earths ECU-ABS:

pin 10,20,34 & body (earth) = 0 ohm
connect battery,
pin 1 & earth = 12V ( ignition key in MAR position)


Mainly when:
1. conrtol lights on when ignition is on (engine running) = there is problem with ABS unit, earth, or power supplu to unit, or relays
2 control lights on after few meters of ride = 90% of chance that one of the sensors is dead

hope this helps.

regards

WS

[Finn]

Brilliant! Thanks

Tested the resistances and earths and pin 1 voltage and all tested ok. Seems like the next step is to test with a new ABS ecu. Noticed also there's one for sale in the shop

[Xti]

Same problem here, ABS light stays on and can't fint test connector T1...

Also (!) brake fluid level /hand brake light is on and it goes off only when braking during traveling. Will check fluid level to see if that might be the problem.

[Suzumushi]

Brilliant! Thanks

Tested the resistances and earths and pin 1 voltage and all tested ok. Seems like the next step is to test with a new ABS ecu. Noticed also there's one for sale in the shop

ok last things to check

1) on engine running check 12v on pin 15 (it;s connected to alternator)

2) pin 29 and 33 are operated by connector on brake pedal

3) and last one (beside accelerometer sensors) -> try to disconnect pin 3 (that comming from ecu pin 14) and instead connect 1k ohm resistor connected to earts (body for example)

if that will not show where error is, you can check to replace accelerometers for test, and if it's not resolving problem abs unit is probably broken... or abs pump

regards

w

[Alfa Patch]

My car also has and ABS issue which I found recently when I swapped the dash over. Seems a previous owner did a nice fix and removed the bulb. I had to smile when I realised!