P38A ABS & TC fault. - FIXED!

[DanClarke]

Only came up immediately after a very hefty plant of the right foot.
Looking in the logs with Nanocom it says front right sensor x 6 counts.
Cleared the logs but the fault pops straight back up again with ABS & TC messages.
Does the car need to go for a little drive to reset the WABCO-D ECU?
i.e. see valid inputs from the sensor again?

 

[wammers]

Only came up immediately after a very hefty plant of the right foot.
Looking in the logs with Nanocom it says front right sensor x 6 counts.
Cleared the logs but the fault pops straight back up again with ABS & TC messages.
Does the car need to go for a little drive to reset the WABCO-D ECU?
i.e. see valid inputs from the sensor again?

The hub bearing could be slightly worn and a sudden application has pushed the sensor away from the reluctor ring. Push the sensor in until it touches the reluctor ring. See what you get, if it sorts the problem think about a hub bearing.

 

[romanrob]

Nanocom has been known to apparently say left when it means right - at any rate, you may want to clean out and re-grease (anti-seize) the housings on both sides and not just assume you only need to do front right. Don't be tempted to whack the sensor with a hammer/ mallet, or you may damage the small dome on the end of the sensor, which is part of the all-important gap.
If you roll fwd at less than 2 or 3 mph you will see the live data on nano - all 4 wheels should flash up with the same speed, and the sensors should go live at the same time after you start moving. This should give you visual confirmation (or not) of what the fault reporting is telling you.
The diagnostic session will terminate when you're rolling (ie when the ABS light normally goes off on the dash)

 

[DanClarke]

Thanks both @wammers & @romanrob
Strangely, it was this self-same sensor that threw the wobbler last time, and was replaced.
Will pop the wheel off and see if the sensor has worked its way out a bit after a thump from the many potholes round here.

 

[romanrob]

Dan, you shouldn't need to take the wheel off, but of course you can if you want

 

[Grrrrrr]

Nanocom has been known to apparently say left when it means right - at any rate, you may want to clean out and re-grease (anti-seize) the housings on both sides and not just assume you only need to do front right. Don't be tempted to whack the sensor with a hammer/ mallet, or you may damage the small dome on the end of the sensor, which is part of the all-important gap.
If you roll fwd at less than 2 or 3 mph you will see the live data on nano - all 4 wheels should flash up with the same speed, and the sensors should go live at the same time after you start moving. This should give you visual confirmation (or not) of what the fault reporting is telling you.
The diagnostic session will terminate when you're rolling (ie when the ABS light normally goes off on the dash)

Yes, you're right and I think it was the WABCO-D that did it but not sure which screen. @martyuk did a post on it somewhere.

 

[wammers]

Yes, you're right and I think it was the WABCO-D that did it but not sure which screen. @martyuk did a post on it somewhere.

There were a couple of things transposed. One of them being the temp controls on the HEVAC.

 

[DanClarke]

Well I took the wheel off so that I could see things a bit more clearly. You are right @romanrob it can all be done withthe wheel in situ, but taking wheels off is so much fun isn't it?
I took the sensor out and slid it back in again with no drama.
Sensor looks to be in perfect nick, but, on looking at "Inputs" in Nanocom all are saying 2.33v except the front right which shows 0.0v.
I wondered if the connector had popped so I disconnected the sensor at the plug and then saw a fresh message in the error log "Front Right short to another". So it clearly knows which sensor the front right physically is.
Cleared all faults and reconnected the sensor; looked at inputs again, still 0.0v on front right. So, is the cost of a new sensor worth a gamble as the next step? I "could" swap front left & right , but that's inviting even more trouble I fear.

 

[wammers]

Well I took the wheel off so that I could see things a bit more clearly. You are right @romanrob it can all be done withthe wheel in situ, but taking wheels off is so much fun isn't it?
I took the sensor out and slid it back in again with no drama.
Sensor looks to be in perfect nick, but, on looking at "Inputs" in Nanocom all are saying 2.33v except the front right which shows 0.0v.
I wondered if the connector had popped so I disconnected the sensor at the plug and then saw a fresh message in the error log "Front Right short to another". So it clearly knows which sensor the front right physically is.
Cleared all faults and reconnected the sensor; looked at inputs again, still 0.0v on front right. So, is the cost of a new sensor worth a gamble as the next step? I "could" swap front left & right , but that's inviting even more trouble I fear.

Check the sensor feed for voltage should be around 5 volts. Check the sensor for continuity. Should have a small resistance. Cannot remember what that is but if you have continuity through it it is fine no continuity it's duff. The voltage creates a magnetic field the reluctor ring passing it causes the field to fluctuate and gives you a signal.

 

[DanClarke]

Check the sensor feed for voltage should be around 5 volts. Check the sensor for continuity. Should have a small resistance. Cannot remember what that is but if you have continuity through it it is fine no continuity it's duff. The voltage creates a magnetic field the reluctor ring passing it causes the field to fluctuate and gives you a signal.

Thanks @wammers Will do.
If I pull the connector that is on the inner wing bracket I should see 5v across the 2 pins then That's easy enough to check.

 

[Datatek]

Thanks @wammers Will do.
If I pull the connector that is on the inner wing bracket I should see 5v across the 2 pins then That's easy enough to check.

Not sure if you will 5 volts across the 2 pins, you should see 5 volts from one pin to chassis, the other pin is the signal return I have not checked to see if you get 5 volts across the pins.

 

[DanClarke]

Not sure if you will 5 volts across the 2 pins, you should see 5 volts from one pin to chassis, the other pin is the signal return I have not checked to see if you get 5 volts across the pins.

OK, will check both leads to ground.

 

[wammers]

Not sure if you will 5 volts across the 2 pins, you should see 5 volts from one pin to chassis, the other pin is the signal return I have not checked to see if you get 5 volts across the pins.

Would be across pins i would think.

 

[DanClarke]

OK, I put a test probe onto each of the 2 wires out of the harness.
One has 3V, the other has 0v.
Nanocom is seeing 0v returned from this ABS Sensor and all other sensors are presenting 2.33v when stationary.
I suspect the sensor has gone open circuit. Looked fine no apparent damage when I pulled it today.
Another is being delivered tomorrow. Will update after I have fitted it. Thanks all.

 

[Datatek]

OK, I put a test probe onto each of the 2 wires out of the harness.
One has 3V, the other has 0v.
Nanocom is seeing 0v returned from this ABS Sensor and all other sensors are presenting 2.33v when stationary.
I suspect the sensor has gone open circuit. Looked fine no apparent damage when I pulled it today.
Another is being delivered tomorrow. Will update after I have fitted it. Thanks all.

You might like to check the voltage on the other front sensor, 3 volts sounds low and the WABCO D ECU is known to suffer problems.

 

[DanClarke]

You might like to check the voltage on the other front sensor, 3 volts sounds low and the WABCO D ECU is known to suffer problems.

Thanks Keith, I shall do.

 

[DanClarke]

UPDATE:
Part arrived at lunchtime.
Did some further testing before fitting it (Front Right) sensor.
Pulled the connector on the Front left and probed for voltages there. Same as the Front Right Socket 3.3V on one pin.
Measured the resistance across the pins of the new part 1.4kOhms.
Pulled the old existing ABS sensor off the front right and measured the resistance across that, did not register any reading (other than Out of Range) until I put it on the 2Meg Ohm range , at which point it said 1.04 megOhms..
Put the new sensor on, cleared the faults with Nanocom, no more ABS/TC fault messages on ignition on. Test drove and all OK.
So definitely a duff sensor. Why it went kaput after a thrash I don't know.

Q. Why/how would thick black sooty grease get deposited on the end of a sensor? Does this imply a leak from the hub?
Other bad news to come.... the suspension bags look really gnarly and cracked.

 

[wammers]

UPDATE:
Part arrived at lunchtime.
Did some further testing before fitting it (Front Right) sensor.
Pulled the connector on the Front left and probed for voltages there. Same as the Front Right Socket 3.3V on one pin.
Measured the resistance across the pins of the new part 1.4kOhms.
Pulled the old existing ABS sensor off the front right and measured the resistance across that, did not register any reading (other than Out of Range) until I put it on the 2Meg Ohm range , at which point it said 1.04 megOhms..
Put the new sensor on, cleared the faults with Nanocom, no more ABS/TC fault messages on ignition on. Test drove and all OK.
So definitely a duff sensor. Why it went kaput after a thrash I don't know.

Q. Why/how would thick black sooty grease get deposited on the end of a sensor? Does this imply a leak from the hub?
Other bad news to come.... the suspension bags look really gnarly and cracked.

And there you jolly well go.

 

[Datatek]

UPDATE:
Part arrived at lunchtime.
Did some further testing before fitting it (Front Right) sensor.
Pulled the connector on the Front left and probed for voltages there. Same as the Front Right Socket 3.3V on one pin.
Measured the resistance across the pins of the new part 1.4kOhms.
Pulled the old existing ABS sensor off the front right and measured the resistance across that, did not register any reading (other than Out of Range) until I put it on the 2Meg Ohm range , at which point it said 1.04 megOhms..
Put the new sensor on, cleared the faults with Nanocom, no more ABS/TC fault messages on ignition on. Test drove and all OK.
So definitely a duff sensor. Why it went kaput after a thrash I don't know.

Q. Why/how would thick black sooty grease get deposited on the end of a sensor? Does this imply a leak from the hub?
Other bad news to come.... the suspension bags look really gnarly and cracked.

So, I have learnt something,it's not 5 volts at the sensor but 3.3 volts
Pleased you got it fixed.

 

[DanClarke]

So, I have learnt something,it's not 5 volts at the sensor but 3.3 volts
Pleased you got it fixed.

One other minor detail was that the 3 original ABS Sensors reported a perfect 2.33V in Nanocom on stationary vehicle ignition on (only time the Wabco-D module can be contacted by Nanocom). The new OEM one only reports 2.13V.
The Wabco ECU seems not to mind though.