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ABS Warning Light


bishbosh
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The Bishtail just failed its MOT because the ABS warning light is not illuminating and then extinguishing on start up.

I am hoping it is just the bulb - anyone know what part number? 92 RR on a JA chassis.

If it isn't the bulb what do I investigate next?

Cheers,

Bish.

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The Bishtail just failed its MOT because the ABS warning light is not illuminating and then extinguishing on start up.

I am hoping it is just the bulb - anyone know what part number? 92 RR on a JA chassis.

If it isn't the bulb what do I investigate next?

Cheers,

Bish.

There are some relays - under the passenger seat? - relating to the ABS. I presume that the rest of it operates properly? Have you looked at all the fuses?

Chris

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Another MOT station ;)

Or rig the bulb in parallel with the charge light or oil warning light ;)

a savvy MOT man should be able to spot that bodge; you would need a simple timer circuit that lightsthe LED each time the igntion is turned on.

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OK so you want to know why the bulb doesn't light?

Simple - no frikin bulb! The to$$er who had the car before me must have removed the bulb. Of course, as soon as you replace it the ABS light shines nice and bright and doesn't go out when driven :angry::angry::angry::angry:

The scary bit is it's been through 3 previous MOT's in my ownership atr the same garage and passed them all!!! Do I have any comeback? No, I didn't think so. :angry::angry:

So, looks like an expensive bit of diagnosis and bit replacement coming up :(

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OK so you want to know why the bulb doesn't light?

Simple - no frikin bulb! The to$$er who had the car before me must have removed the bulb. Of course, as soon as you replace it the ABS light shines nice and bright and doesn't go out when driven :angry::angry::angry::angry:

The scary bit is it's been through 3 previous MOT's in my ownership atr the same garage and passed them all!!! Do I have any comeback? No, I didn't think so. :angry::angry:

So, looks like an expensive bit of diagnosis and bit replacement coming up :(

Nope - very cheap bit of diagnosis :) Can't make any promises about the repairs that follow it...

Grab a copy of the workshop manual and find the bit with the ABS codes and instructions for interogating it with a bit of wire (hi tec stuff, this). There are two bits in the manual that talk about diagnosing ABS faults - one just says plug it into a Testbook, the other gives full details of how to do it yourself, and they're in completely different sections of the manual.

I'll have a look and see if I've still got printouts around, but you remove a relay (green, from memory) which is behind the side cover of the passenger seat base, then short out two pins of the ABS diagnostic connector which is behind the inspection hatch at the front of the same seat base. Can't remember if you short it then turn the ignition on or the other way round, but this then causes the ABS light to flash error codes (which are in the manual) and will tell you exactly what it's unhappy about. It will flash the same code repeatedly until you clear that error by disconnecting the shorted pins while it's flashing the code. You then start the process again to get the next error and so on until all errors are cleared.

If you're really lucky you might not need to do anything else - at least take the truck for a spin and see if any new errors appear, as you could have errors which have been sat in the system for ages and are no longer relevent.

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.... and the chances are the fault code is pretty accurate at telling you the problem;

had the ABS lamp come on in the volvo, diagnosed it m'self and haynes listed is as brake pedal sensor (garage said, accompanied by the usual teeth sucking noises, you need new ABS, £ 500 to you blah blah) so I said replace the sensor and we'll see and that sorted it.

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Well,

Thanks to Geoff's info, I have managed to obtain the fault codes that the ABS system is giving. These have been read, cleared, road tested and re-read and they all come back :( :

2-6 Brake Light Switch

2-8 No voltage to ABS solenoid valves

3-0 Inlet front right

3-3 Outlet front left

3-5 Outlet rear right

3-8 Inlet isolating

4-2 Inlet front left

4-4 Inlet rear right

4-5 Outlet rear right

4-6 Inlet rear left

4-8 Inlet isolating

4-9 Outlet isolating

Interestingly, codes 3-5 and 3-8 didn't appear on the first run through - they appeared after I had removed the multiplug from the solenoid block, tested for continuity and voltage and refitted it.

All pins on the connector were OK for continuity and gave 6V on each pin (which kind of contradicts code 2-8. Dunno if that is good or bad, judging by the number of codes atributed to the solenoid block it looks more like the latter :( .

I think the best way forward for long term reliability and low maintenance costs is to fit the non ABS system from the Discovery I have I the garage. However, I would be interested to hear from anyone who thinks they know how to take these fault codes forward and remedy them....

As far as the MOT goes, I presume I only have to notify the testing house that the vehicle does not have ABS? I will of course notify my insurer as well if I do the swap...

Any opinions out there....?

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Hi,

In my opinion it would probably be easier to repair the ABS than take it out!

First things first, check the brake light switches and their adjustment, there's more than one.

Then test the ABS relays and fuses.

You will probably find all the other fault codes are "phantom" and caused by the lack of power to the valve block.

IIRC the system does not supply any power to the solenoids until the vehicle has achieved the 5mph mentioned, I think it's likely the valve relay that does this has failed (or the fuse has blown).

There are 3 relays in the system, the warning lamp relay which you have obviously found, the next one to it is the valve relay and the last is the pump relay.

HTH, Shaun.

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I have checked the relays and all is well (the two next to the lamp relay are interchangeable). It is true that the brake pedal switch may be the culprit as I don't think I get a click before the click accompanied by the hiss of the booster. However, I don't want to head off down the road of swapping out parts in an attempt to find out which bit is actually malfunctioning - it will get very expensive very quickly.

Anyhow, it shouldn't be that difficult to remove the ABS should it....? :unsure:

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not that difficult as you have a disco to Rob from but..

what about your insurance?

[harbinger of doom]have an accident and they find you've removed the ABS=a day in court at least=no insurance or worse being liable[/harbinger of doom]

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PS

I bet they ask for an engineers certificate (not a "I can swim a length" type certificate)

to do it properly you'll need to remove/plug all the sensor holes

or fit new swivel pins(front)

change all the brake lines/compensator(if fitted)

I'd use the complete Disco set up even consider using the front axle from the Disco complete

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Ah but watching the tdi's struggle on hills (no names to protect JST's reputation :unsure: ) while me and Tim simply powered up them with this ---> :D look on our faces is worth it B)

OK the water was a different matter though :rolleyes:

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You will probably find all the other fault codes are "phantom" and caused by the lack of power to the valve block.

I'm no expert on the ABS system, but I'm with Shaun on this one - I'd guess you have at most two problems (the brake light switch may well be separate - but that should be dead easy and cheap to fix). 2-8 No voltage to ABS solenoid valves will cause all the following errors, so at this stage you can reasonably assume there's nothing wrong with the valves themselves.

Might just be a dodgy earth or something like that?

Put a bit of effort into fixing the ABS before you ditch it - mine doesn't work at the moment, and it makes a big difference to both the distance I can stop the truck in and how much control I have under heavy breaking.

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