ABS Warning Light Staying On!!

[admiral51]

Have a look at this topic

Colin

Good topic Colin thank you. Only thing is I have to confess I'm a bit of a novice when it comes to cars and from looking at the pics it looks a bit too technical for me to be tackling!!!

Give me a computer any day and I'm well away ha ha!

I have the same problems with cars and computers

I had to check and see which one of my sensors were misbehaving and i managed to use the aforementioned picture to track it down so it cant be that hard if i can do it

Have the ignition off and remove the plug from the ABS ECU which is sat just in front of the LHM resevoir and behind the fusebox.Then with a multimeter set to ohms just test across the pins as dictated on the plug not the ecu .A reading of 1053 IIRC is a good reading anything else is not good.
Thanks to CitroJim for the above destructions as me and electronics just dont get on well

Colin

[brmartyn]

UPDATE

Just returned home from having a quick drive and about 30 seconds after I set off the ABS light went off - GREAT STUFF!!!

Or so I thought until a few minutes later it came back on again - TYPICAL!!

[CitroJim]

That's an almost classic symptom of a sensor going home or a dodgy connection.

Do you have a digital multimeter Brady as the tests are not hard to do.

Disconnect battery and remove the plug to the ABS ECU (between the LHM reservoir and fusebox)

Refer to the post-98 picture...



Set your digital meter to the ohms range that will read up to about 2K Ohms.

Place the probes on each pair of pins in the ECU plug (not the ECU itself!) that correspond to each sensor and read the value in ohms.

A good sensor will read around 1080 ohms or thereabouts. You'll likely see three reading very similar and one reading a little different. The one that reads a little different is the duff one.

the resistance value is critical and they don't need to drift far from 1080 ohms before the ECU rejects them as good sensors. If one reads say 1100 ohms, that'll be enough to make it duff in the eyes of the ECU.

If you do find one reading a little high, check its connector.

[brmartyn]

That's an almost classic symptom of a sensor going home or a dodgy connection.

Do you have a digital multimeter Brady as the tests are not hard to do.

Disconnect battery and remove the plug to the ABS ECU (between the LHM reservoir and fusebox)

Refer to the post-98 picture...



Set your digital meter to the ohms range that will read up to about 2K Ohms.

Place the probes on each pair of pins in the ECU plug (not the ECU itself!) that correspond to each sensor and read the value in ohms.

A good sensor will read around 1080 ohms or thereabouts. You'll likely see three reading very similar and one reading a little different. The one that reads a little different is the duff one.

the resistance value is critical and they don't need to drift far from 1080 ohms before the ECU rejects them as good sensors. If one reads say 1100 ohms, that'll be enough to make it duff in the eyes of the ECU.

If you do find one reading a little high, check its connector.

Thanks once again Jim that really helps. Again I don't want to sound like a novice but when disconnecting the battery do I disconnect the positive or the negitive first or doesn't it matter? and how about connecting them back up?

Also will disconnecting the battery effect other things in the car like the radio for example?

I just need to find a digital multimeter now!

[CitroJim]

Disconnecting the battery will cause the radio to loose its code but that's about all.. be sure to have the radio code to hand.

Disconnect just the battery negative lead and tuck it well out of the way. All will be perfectly safe then.

On reconnection, the alarm will go off but this can be reset using the plip.

If you really don't want to disconnect eh battery, you may be OK just pulling out the ABS fuse. This is F1 (20A - yellow) in the engine bay fusebox but to be 100% safe I'd disconnect the battery.

[brmartyn]

Disconnecting the battery will cause the radio to loose its code but that's about all.. be sure to have the radio code to hand.

Disconnect just the battery negative lead and tuck it well out of the way. All will be perfectly safe then.

On reconnection, the alarm will go off but this can be reset using the plip.

If you really don't want to disconnect eh battery, you may be OK just pulling out the ABS fuse. This is F1 (20A - yellow) in the engine bay fusebox but to be 100% safe I'd disconnect the battery.

Now there's a thing - the radio code
What could happen if I didn't disconnect the battery

[CitroJim]

You risk damaging the ABS ECU.

As I say, you should be OK just pulling the ABS fuse. I'm going to check the wiring diagrams to see if just removing F1 does in fact fully isolate the ABS ECU...

Be right back...

[brmartyn]

You risk damaging the ABS ECU.

As I say, you should be OK just pulling the ABS fuse. I'm going to check the wiring diagrams to see if just removing F1 does in fact fully isolate the ABS ECU...

Be right back...

Cheers Jim

[CitroJim]

Checked the circuit. If you pull F1 in the engine bay fuse box and F6 (10A - red) in the dashboard fusebox (under the cover by the your right knee), the ECU will be totally isolated and it will be safe to disconnect the ABS ECU plug.

To disconnect the plug, pull up the red plate on the side of the plug facing you. This plate locks the plug to the ECU and it can be quite a pull. As you pull the red plate up, the plug will start to slide off. You can just se bits of this red plate in the picture.

Replacement is a reversal.

Radio code is a problem. Visit a Stealer with your VIN and proof of ownership (V5C) and he will furnish you with it for a small sum. Before that, look in your owners handbook pack for a card with it on (a four digit number) and look on all pages of all books as it is often scribbled down somewhere... Try the audio book...

[Peter.N.]

Won't it be isolated when he pulls the plug out Jim?

[CitroJim]

Won't it be isolated when he pulls the plug out Jim?

Yes, trouble is Peter, it will be when the plug is reconnected. There will be 12v there and it could "spike" the ECU and upset it.

Normally, it's Ok to pull the plug out when power is on but the harm can be done when reconnecting it...

I'm not a fan of "hot-swapping"...

[brmartyn]

I've sourced a multimeter from a friend so I will give this ago tomorrow

Wish me luck

[xantia_v6]

Radio code is a problem. Visit a Stealer with your VIN and proof of ownership (V5C) and he will furnish you with it for a small sum.

As I have said before, it is worth trying the dealer who sold the car new, as they often kept a private note of the code (in case they later disconnected the battery while servicing the car), and some will give this for free.

[Peter.N.]

Won't it be isolated when he pulls the plug out Jim?

Yes, trouble is Peter, it will be when the plug is reconnected. There will be 12v there and it could "spike" the ECU and upset it.

Normally, it's Ok to pull the plug out when power is on but the harm can be done when reconnecting it...

I'm not a fan of "hot-swapping"...

Oh right! Perhaps I'm braver than you - or more foolhardy

[brmartyn]

Disconnecting the battery will cause the radio to loose its code but that's about all.. be sure to have the radio code to hand.

Disconnect just the battery negative lead and tuck it well out of the way. All will be perfectly safe then.

On reconnection, the alarm will go off but this can be reset using the plip.

If you really don't want to disconnect eh battery, you may be OK just pulling out the ABS fuse. This is F1 (20A - yellow) in the engine bay fusebox but to be 100% safe I'd disconnect the battery.

OK I've got some readings

Rear Left - 1020
Front Left - 1033
Rear Right - 1022
Front Right - For some reason I couldn't get an accurate reading on this one but it never read more than 400

Looks like front right is at fault would you agree?

What's the next stage