P38A Front Wheel ABS Speed sensors

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awkwardbob

awkwardbob

Well-Known Member
Posts
590
Location
Glasgow
Hi,
I’m having a wee issue with my ABS.
I’ve the yellow warning lamp on the dash but no error message.

Nanocom reports no ABS faults but I did notice that, while the rear wheel
Sensors register road speed correctly, the fronts resolutely remain at 0mph.

Is this likely the source of the problem ? Ie. As part of its check, the system isn’t registering the road speed necessary to reset the warning indicator.
If so, is there a way of adjusting these ? (Where physically are they and what do they look like ?)
As it’s both front wheels, could it be something electrical like a fuse or relay common to both ?

thanks in advance for any help
Or advice !

Bob
 
awkwardbob said:
Hi,
I’m having a wee issue with my ABS.
I’ve the yellow warning lamp on the dash but no error message.

Nanocom reports no ABS faults but I did notice that, while the rear wheel
Sensors register road speed correctly, the fronts resolutely remain at 0mph.

Is this likely the source of the problem ? Ie. As part of its check, the system isn’t registering the road speed necessary to reset the warning indicator.
If so, is there a way of adjusting these ? (Where physically are they and what do they look like ?)
As it’s both front wheels, could it be something electrical like a fuse or relay common to both ?

thanks in advance for any help
Or advice !

Bob
Click to expand...
Could be wear in front wheel bearings causing working gap to go out of range. Push both sensors in until the are in contact with rotor and see what you get.
 
wammers said:
Could be wear in front wheel bearings causing working gap to go out of range. Push both sensors in until the are in contact with rotor and see what you get.
Click to expand...

I’ll have a go at that.
I’m just a wee bit suspicious as the issue only appeared after I had the dash out to re-bulb it, and odd that it’s both front sensors..

-that’s assuming, of course, that the yellow
ABS light hadn’t blown (or been removed) and the faults been there all along !
 
awkwardbob said:
I’ll have a go at that.
I’m just a wee bit suspicious as the issue only appeared after I had the dash out to re-bulb it, and odd that it’s both front sensors..

-that’s assuming, of course, that the yellow
ABS light hadn’t blown (or been removed) and the faults been there all along !
Click to expand...
ABS lamp should come with ignition flicker then stay on until road speed passes 5 MPH.
 
Yes, it does that now but stays on.
No fault codes in the ABS nor anything in the info centre so suspect it may be that it’s not registering speed.
Can’t remember if that bulb worked or not before replacement, I only remember the red handbrake one (I think)
 
awkwardbob said:
Yes, it does that now but stays on.
No fault codes in the ABS nor anything in the info centre so suspect it may be that it’s not registering speed.
Can’t remember if that bulb worked or not before replacement, I only remember the red handbrake one (I think)
Click to expand...

They won't register speed if the gaps are too large
 
What year car? Does it have 4W TC?

@wammers can you swap sensors front to back? Thinking he could see if the fault moves and check continuity and resistance at the same time. Sure someone posted expected resistance on here somewhere.
 
Grrrrrr said:
What year car? Does it have 4W TC?

@wammers can you swap sensors front to back? Thinking he could see if the fault moves and check continuity and resistance at the same time. Sure someone posted expected resistance on here somewhere.
Click to expand...

No. Early ones only go in the one position. Later ones can be swapped side to side but not front to rear.
 
It’s a ‘97 Gems 4.6, I’ll have a rummage around tomorrow.
You reckon the resistance from the sensor going to the ECU should be 100-1000 ohms ?
I can have a check of that if I can find where the connector lives !
 
wammers said:
No. Early ones only go in the one position. Later ones can be swapped side to side but not front to rear.
Click to expand...
Was talking EAS sensors there silly me. Suppose you can swap around speed sensors just different wire lengths front to rear. You need five volts to the sensor this pulses as wheel rotates giving the signal to the ECU.
 
wammers said:
Was talking EAS sensors there silly me. Suppose you can swap around speed sensors just different wire lengths front to rear. You need five volts to the sensor this pulses as wheel rotates giving the signal to the ECU.
Click to expand...

Is that 5V feed fused anywhere ?
It just seems a bit odd to lose both front sensors simultaneously, -or maybe a less than fully healthy battery ? -that said Nanocom reads 16V with the engine running
 
awkwardbob said:
Is that 5V feed fused anywhere ?
It just seems a bit odd to lose both front sensors simultaneously, -or maybe a less than fully healthy battery ? -that said Nanocom reads 16V with the engine running
Click to expand...
The voltage to the sensors is five. Check them for continuity and for voltage.
 
The 16volt read on nano is a known issue (actually i believe it's not nano but certain becm versions) ignore the 16v and measure yourself...
 
Last edited:
Remove the abs sensors and boots and clean the ****e off them, retrieve the metal cages carefully clean those up too. Lightly grease and replace. Dont hammer them, just a firm push fit... Before you replace them, check the end of the sensor is smooth, with a small convex bump in the middle...which indicates they have not been damaged previously
 
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