[Mk2] [Turbo] ABS Sensor Issue....

[willfinch36]

First of all my ABS light came on, so I did error code check, and it came up with the REAR RIGHT abs sensor was fooked, after managing to get it off, I installed the new one I bought from camskill, however the ABS light is still on? I have reset the ECU and pressed the brake pedal 8 times within 3 seconds etc, but its still on? and when you do an error code check still comes up with 3 3 ??

Any Ideas?

[Si_Crewe]

I just posted summat about a similar thing a couple of weeks ago.

Thing is, the 4 wheel sensors give off a signal and the amplitude AND frequency are measured.
If three wheels are giving similar signals and one is different the ECU assumes the one that's different is at fault.

Here's what happened to me...

ABS light came on.
I got fault 34. Left rear speed sensor.
Garage fitted new sensor.
ABS light continued to come on almost all the time.
12 month interlude.
Decided I needed to fix it for MOT.
Removed left rear sensor and checked it. Noticed that it had some rust particles stuck to it.
Cleaned em off and refitted it.
ABS warning still on.
Had a bit of a think about it.
Removed right rear sensor and discovered a HUGE clump of rust particles stuck to it.
Cleaned em off and refitted it.
Checked front sensors.
Found rust stuck to em all.
Cleaned em off and refitted em.
No more ABS fault.

Thing is, all your ABS sensors get fitted at the same time.
They all pick up crap at roughly the same rate and the metallic crap that sticks to the sensors will make the signal weaker.
Now, the clever bit is that as long as all 4 are giving a roughly similar signal the ECU remains happy.
If one of your sensors packs up and you replace it you end up with one sensor with no crap on it and that sensor is giving a much bigger signal.
The ECU then sees 3 wheels giving similar signals and one giving a bigger signal and flags THAT one up as the fault when, in fact, there's nothing wrong with it.

I know it can be a bu88er removing the sensors. If you can't get them off at least try jet-washing the hubs with the wheel off to try and dislodge as much of the crud as possible off the sensors.

Try cleaning off the left rear one first. If that has any effect you know you're on the right track.

*EDIT*
Incidentally, if you're doing any good the ABS warning light will go off without you having to nonce about resetting the ECU.
It'll still report the fault until you reset the ECU but it won't light the ABS warning.

Also, christ I need to work on being more concise.

[willfinch36]

DOH - found out reason why it was bu88ered... the abs wire had been cut through by the intercooler as my mate didnt strap it out of the way!

[ChrisW]

I had the same thing, but I think in my case the wire had been cut through by the aircon belt. Very frustrating after spending an hour or so trying to change the sensor myself and then giving up and taking it to Rogue!

[willfinch36]

yeah thats basically what had happened to mine as well

[ChrisW]

Yeah you live and learn - 100-odd quid for a new ABS sensor (plus labour costs) when all that was needed was a bit of soldering!

[willfinch36]

£130 I think!! did it myself though.... and im no mechanic either

[ChrisW]

Mine was stuck in the hub, even Rogue had trouble getting the damn thing out!

[sam1176uk]

Mine is coming up with right rear abs sensor OPEN CIRCUIT whatever that means?! I have tried 2 sensors and waiting on a 3rd.

[ChrisW]

Sounds like the same thing - it's probably the wiring not the sensor.

[sam1176uk]

Does the wire not run up from the hub into the engine bay, doesnt seem to be anything it can catch on?

[ChrisW]

If it's not clipped in properly where it runs through the engine bay then it can rub against one of the belts. In my case I suspect I disturbed the wiring when I installed my intercooler fan.