Brake warning light on dashboard.

[bongoroy63]

I had the ABS warning light come on on the dashboard just before Christmas.
Does this light come on when the brake pads are low as a warning to change them or is this likely to be something more sinister?
I’ve never had this before so a little bit concerned. I can cope with changing the brake pads. I know some will say ‘just have a look at the pads’ but I really don’t want to be taking the wheels off this time of year if I don’t need to.

[g8dhe]

ABS is the Anti-lock Braking System, its when one wheel (or more) locks and starts to skid, it releases the braking and allows it to gain a grip again, hence the rapid juddering when it operates. It doesn't tell you anything about the brake pads themselves at all.

[bongoroy63]

Thanks for the reply. 2 further questions:

1/ The ABS light is permanently on. Should this be the case if what you say is correct?

2/ How do I diagnose the problem?

The brakes do feel a bit spongy, this is what made me think it might be the brake pads wearing down.

[Roy748]

I recently had the ABS light illuminated on my citroen berlingo, turned out to be a worn wheel bearing triggering the sensor. Might be worth examining.

[g8dhe]

If the light is on then the computer is reporting a problem you need to read the error code from the diagnostic socket;
http://www.philmcfadden.co.uk/MazdaDiagnosticBox.htm

[Ian]

95% of the time it is a sensor that needs replacing. To establish which sensor is faulty use the diagnostic instructions as above. Alternatively you can test each sensor by using a multi-meter on the sensor leads. If you don't get a reading of between 1600 and 1640 ohms you have found the culprit.

[bongoroy63]

Thanks Ian, that sounds like a plan.

Nothing is ever straight forward with a Bongo is it? I have a basic diagnostic tool and this afternoon I decided to give it a go. No, it’s a completely different fitting isn’t it?
Do garages have a variety if fittings for different vehicles? I thought they were all the same!!

[TheLongRoad]

Thanks Ian, that sounds like a plan.

Nothing is ever straight forward with a Bongo is it?

Just defending the old Bongo’s, any older (or newer) vehicle can suffer an ABS sensor failure. However, at least the Bongo computers store history data that hopefully tells you which wheel to check. Sometimes you just need to unplug and clean the contacts then plug back in. Then clear the fault code and take the Bongo for a spin

[Mrs Feynmans Bongos]

My ABS orange warning light never went off, a month ago.

Since removing headlights, fairly sure I have now found the front wheels' ABS connectors O-03, O-04 (although I couldn't find the Control Unit connector O-01, buried too deep under leisure battery etc for bonnet access).

Unplugging O-03 N/S/F, my cheap multimeter across pins in socket (bright yellow inside) reads 1440 ohms. Whereas aross pins on O-04 O/S/F is always open circuit.

So it seems fairly clear drivers side ABS sensor has failed. I have 2 questions:
.
- 1440 ohms on N/S/F is 12% below the healthy range 1600-1640 quoted here on Fury. My cheap meter, something else in parallel, or unhealthy so may also be failing?

- Are the RTG sensors on eBay ok https://ebay.us/m/e9aABL, is it best to pay £60 with new brackets, or £40 without?

Advice appreciated

[g8dhe]

Its a fairly common problem, the resistance values do seem to vary quite a bit but that can be part of the problem if the cable is damaged then moisture gets in causing the value to read lower than expected! The drivers side seems to suffer this problem or at least gets reported more often! Mine went earlier this year but diagnosed by using the diagnostic box and counting the flashes etc.

[Mrs Feynmans Bongos]

Thanks for replying Geoff.

O/S/F is open circuit thus DEAD, indeed looks like connector O-04 has suffered some ingress.
For N/S/F, connector O-03 looks fine but only 1440 ohms across pins. Maybe shows ingress has started here too?

Can't see my ABS brackets, but would I be daft not to get a new one bundled with O/S/F sensor, in case the garage finds original bracket too corroded for reuse?

[g8dhe]

Can't really advise on that, sometimes you can get just the sensor other times the whole lot is advertised. The actual sensor is identical for nearly all vehicles and its just the plug and cable length that varies hence lots of Youtubes showing using "different" sensors being used by altering the plug.