Alfa Romeo Forum banner

ABS light does NOT come on!

7K views 31 replies 9 participants last post by  Tacconi 
#1 ·
Mentioned this in a previous thread but still can't get to the bottom of it!

My ABS light does not come on at all when the key is in the MAR position.

I have checked the indicator bulb and even swapped speedo binnacles over but still the light does not come on.

Even creating a fault by detaching one of the wheel sensor connectors does not cause it to come on.

However the brakes won't lock up on emergency braking so the system appears to be working.

Can only assume it's a wiring fault somewhere but where to look?

Any ideas anyone please? :confused:
 
#2 · (Edited)
The ABS warning light is not a bulb, it is a LED in the instrument cluster.

The LED is connected to the switched 12V and pulled to ground at Connector A pin 18. See wiring diagram for instrument cluster.

The control is done by the ABS unit. I don't know if your car is a PH1 or PH2 so I have attache the wiring diagram for both.
 

Attachments

#6 ·
Somethings happening. A resistance check in the led socket as you turn the ignition on should show a closed circuit, if not do the same check following the wire back through each connector until you get to the ECU pin. Hopefully digging around under the dash will restore continuity to the circuit. Last resort would be to put your own wire in, but I would shy away from that idea. Its most likely a miss crimped spade in there somewhere, or unlikely a failed board component(diode, dry joint) in the ABS ECU. Has the ECU got a dedicated earth path for the ABS light? Just be methodical and use your eyes!
 
#9 ·
Its a one off fault that can be sorted, just a bit of an adventure I'm sure you can sort out. Make yourself some fine pointy probe tips and start looking for the coloured wire at the respective connections, theres only a couple by the looks of things! You are spoilt by having a wire diagram.
 
#10 ·
Earth the contact on A18 at C10 the instrument cluster whilst the engines running, led for ABS should then illuminate.

Connector A is the white one lower left on the instruments.

Should be able to disconnect pull it forward and get a probe on the contact.

Good luck.
 
#14 ·
If you recall, I tested the resistance between ABS unit and car body. It was fine. That doesn't rule out an intermittent problem of course, but the fact that the ABS light came on when pin 1 was connected to the ABS unit body and that the ABS appears to function in a brake test is indicative that the earth isn't a problem.
 
#15 ·
That's what I thought but who knows with Alfa electrics! lol Was unable to strip the ECU down in situ inspite of removing the brake fluid reservoir and relay fuse box so will have to take it to Marco.

Air-bag light is back on again - after changing the headlight dip beam bulb!!! arrrrrrrrgh!:cry:
 
#17 ·
You'll learn where all the connectors are in time lol. Take the ECU out, if you're careful with the reservoir you won't have to bleed the brakes! Sounds like you have some damp issues with the electrics and earths, lots of electrical cleaner n copper grease, maybe crimp in some new earth terminals?
 
#21 ·
Just a update on the above, on investigation i've found pins 3 and 4 are incorrect on the phase 1 wiring diagram they should be transposed to be correct. signal LTB-WHT wire is on pin4, earth BLK wire is pin3 of the square ECU connector G272.

Alfa_Awfulsod Thanks for the original post, I hadn't even noticed my ABS had no warning light on startup.

New ABS module ECU sorted mine. Bought the 0 265 204 001 block and ECU off Ebay in Tokyo! only one i could find :)

MOT next!!!
 
#24 ·
Can't you bend the taps up and ply it apart, or is it molded into a block of resin? Ring around ECU repairers, some may take on the work FOC, but you may have to pay their postage rates? Not a shared part that could be reprogrammed for your car? Good luck with the hen's teeth, they aren't that rare!
 
#29 ·
Hello

I still have a problem with my ABS unit not iluminating the warning light on the dash, I also have a simular problem With the charging light not iluminating, the battery are charing With 14,2 V so ok there

Anyone know if the two problems can be the same?

Does anyone have a wiring diagram for the binnacles and the charging system ? I am interested where the 12V to the light bulbs/ LED comes from ? ,

If anyone want to sell me a copy of a repair CD I would like that ;-)

Regards

Chris
 
#30 ·
You haven't mentioned what model your car is.
Is it a Ph1 or and Ph2? The instrument cluster is different between the two models.

Do you have problem with other indicator lights.
The 12V for the ABS and Generator light come from the same line.
It is the key-operated 12V on pin 2 on the B connector on the instrument cluster.
If this voltage isn't present you will also have problem with the following warning lights:


  • Airbag light
  • Door open lights
  • Passenger Airbag deactivation light
  • Check Engine light
  • Luggage Compartment open light
  • Bonnet open light
  • Oil Pressure light
  • Brake Pad light
  • Code light
 
#32 ·
Hello
Problem solved.
Both my binnacle and the ABS ECU had to be changed, but left me With a ABS illuminating on the dash, then I put Earth to the ABS testerplug and read out the code on the ABS light , it said ABS sensor defectiv, measures the sensors they where oki, the it was the wiring left, found a broken wire where it Connects to the ABS ecu, solded and all OK, thanks to Henrik for help ;-)

Regards
CHris
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top