ABS Warning Light permanently on

  • Hi I'm new to the club having bought an MX-3 1 week ago.
    She's a 1.8 V6 1998 model and in good nick apart from the ABS problem.
    I've read all relevant posts regarding ABS and wonder if anyone can help.
    I've taken each wheel off in turn and the front N/S sensor looks as if it has been replaced. It was easy to remove the 2 12mm (spanner size) bolts.
    The other 3 sensor fixing bolts are well rusted in and my 12mm socket wouldn't undo them.
    I've got a Chilton manual but for 1990 / 1993 cars (mines 1998). The book shows fault codes 11,12,13,14,15,22,51,53,61 for ABS sensor / harness / relay and control unit checks. But with my car do these codes appear on the diagnostics unit mounted on the bulkhead behind the battery or is there a separate ABS diagnostics unit somewhere else in the car?
    An article I've read for the Ford Laser advises short pins TEN and Ground and put an LED with a 1k resistor in series across +B and FEN sockets in that diagnostics unit. Is the MX-3 similar?
    Also Marco advises measure 1.5K across each sensor. I'll check that too.
    Has anybody checked the above MX-3 ABS fault codes?

  • the main abs electics are under the passenger seat if that help

  • usually it is the sensors, mine comes on when its been raining nowt I can do really as I dont know which one it is.
    Best thing to do is get another sensor and just keep changing them for the new one until the light goes off, if there is more than one gone then it wont fix it, so it then may be a case of replace all of them and if that doesnt work then look towards other bits.
    Check the pipe too coming from the inlet manifold to the servo, the servo needs a good vacuum to work, if that pipe is leaking I think that sets it off too.
    Yours will be an OBD2 loom and I have an electronic tester for that which will bring the codes up for you

  • Since opening the post I found the MX-3 1995 workshop manual on this website and have printed off the relevant ABS pages. Thanks for advising where the ABS control unit is. I'll start checking it tomorrow.
    I used to work for Philips Electronics selling electronic components to the autos industry (in the good old days when we had one…) I'm looking forward to playing again...
    Thanks again

  • Now removed the passenger seat (3 bolts easy, 4th needed drilling out..)
    Got the ECU out and checked all 4 sensors working fine (each reads 1.3Kohms and gives 1v ish when wheel rotated)
    Now trying to check ECU / relay / and hydraulic unit.
    Anybody got any ideas how to check these out without too much removal??
    Can't wait to get my new car on the road

  • Heres a couple of ideas I have found online

    1, someone found that the alternator wasnt producing the correct voltage and made the ABS light come on, put a tester on the battery with the car running, it should say 14.1v for a correct working alternator
    Also it states that another cause is the battery not working properly so check the battery too

    2, marco found the ABS motor had packed up and he changed that and it worked fine

    3 Sensors covered in crap, this is a biggy, you need to go round 1 by 1 taking off the calipers and the discs and the sensor is hidden behind the disc, make sure all the sensors and teeth are clean ( they collect a lot of crap in there.

    4, try the checklist below and the relay, could be the relay is faulty and not giving current through to the ABS unit


  • Had another go today. Removed the battery tray (or rather chiseled 2 of the rusty 4 6mm bolt heads round until they submitted and loosened..) Unplugged the motor connector , applied 12v but nothing. So I guess its a new hydraulic unit unless its something daft like worn out brushes. I haven't taken the unit out yet. Antbody got any tips? Also should I just let the fluid drain out or is there a way of plugging the pipes? Will the unit lift out without removing gearbox support mount etc?
    Also would the motor have died due to something else failing ie ECU or do they keel over by themselves?
    Has anybody got a not too expensive hydraulic unit I could buy? I'll also check ebay!!
    Thanks for your replies. I'm getting there..

  • If the pipes are rubber, clamp them otherwise let it run out and give it a full bleed through

  • No mention of checking the fuse, might be best to rule that one out first :)

  • Got the hydraulic unit out today.
    I let the fluid seep out the pipes and then washed down with hot water + detergent then rinsed off .
    I took the motor apart.
    2 items have failed:-

    1. The brush connected to the +12v lead was stuck in the brass housing.This was easy to free up.
    2. The ABS pump works by an eccentric cam on the armature pushing against 2 spring loaded plungers on opposite sides of the aluminium housing where the motor fits into the housing itself.

    These plungers are pretty rusted up and I guess it's a replacement unit.
    I'll have a go at freeing them up but I'm not optimistic.
    I've seen these ABS pump units on ebay from dismantlers for around £40 to £50 so this is my next move.

  • The guy I bought my mx3 from offered me a bundle of ABS parts, 3 sensors control unit and the pump, plus a few other odds and sods, wanted 80quid for the lot inc delivery, if you want i can ask him for a number? Hes in birmingham if you needed them in a hurry

  • Hi Jesta,
    I doubt if I'll be able to free up the plungers (or valves) in my unit so I need to get a hydraulic unit from somewhere. The problem is even if the unit looks good it may not function so I need to find a way to test before I fill up and bleed the system etc. (unless the seller does know the unit works fine.)
    I'd be grateful if you would contact him or let me have his number

  • pm'ed

  • any luck?

  • Hi,
    I decided to get the ABS hydraulic pump unit from a scrappie and this arrived last Friday.
    I fitted the unit Saturday without any real problems although spannering up the 6 hydraulic pipes is fiddly.
    On Sunday I bought a Vizibleed brake bleed unit, which is just a length of clear plastic pipe plus a one-way valve, from Halfords for £4.99. I bled the system thoroughly and the pressure on the pedal came up to normal.
    Started the engine and the ABS warning light came on and stayed on…..DAMN.....
    As I started driving the car the warning light then went off... yippee.....
    I have my car back again. MOT is next.

    Thanks to all for the above replies


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