C70: ABS and TRACS OFF light on hard acceleration

[Juular]

1998 T5 2.3 C70 - as the title says these lights come on on hard acceleration especially when kickdown is used.

ABS and TRACS works totally fine when the light is not on.

I read the codes using VOL FCR and it gave ABS 141 EBD Pressure Switch fault.

The switch itself looks perfect and is not leaking. Plug has been removed and cleaned. The light never comes on when actually braking.

I've tried the clothes peg wedged into the ABS module plug trick without success.

Any ideas?

[Juular]

I'm still struggling with this.

The car has been plugged into both vol-fcr and Delphi software. The EBD pressure switch is functioning exactly as it should (reading 0 /off all the way down and 1 / on as the pedal is at the bottom of travel). Yet this ABS 141 is the recurring fault code.

ABS sensors are giving plausible speed readings through Delphi.

The car ran perfectly without any warning lights for 2 weeks. During that time I was using kickdown / hard acceleration quite a lot without any issues at all.

Yesterday it flagged up the ABS/TRACS OFF lights as soon as I put my foot down while exiting a roundabout.

Anything else to try?

[tony209]

Originally Posted by Juular

I'm still struggling with this.

The car has been plugged into both vol-fcr and Delphi software. The EBD pressure switch is functioning exactly as it should (reading 0 /off all the way down and 1 / on as the pedal is at the bottom of travel). Yet this ABS 141 is the recurring fault code.

ABS sensors are giving plausible speed readings through Delphi.

The car ran perfectly without any warning lights for 2 weeks. During that time I was using kickdown / hard acceleration quite a lot without any issues at all.

Yesterday it flagged up the ABS/TRACS OFF lights as soon as I put my foot down while exiting a roundabout.

Anything else to try?

It's worth having a look at the state of your reluctor rings, split or corroded ones can cause various ABS fault codes. A good indicator of a damaged ring is non- working cruise control. I've had 3 split rings so far, one on my V70 (with ABS warning light)caused a low ABS sound on tight lock, the other two on my C70 prevented the cruise control from working - neither through up an ABS warning light but the occasional ABS/TRACS OFF light on hard kickdown.

[cheshired5]

If you can graph the individual wheel speeds, it's a lot more accurate and easy to spot an anomaly with the senors if they are the cause.
Here are my 4 wheel speeds graphed with Vida which basically show that the speeds are so similar, the 4 individual plots merge into one.




If I then wheel spin to trigger the anti-skid, the mismatch in wheel speeds shows clearly.

[Juular]

Not sure why I never thought of checking the reluctor rings, I will give that a go - I have to do the rear brakes anyway.

Cruise control is working perfectly for what it's worth.

[CNGBiFuel]

I've seen this, rings crudded-up and sensor plugs dirty. Wire brush works and/or new rings are dirt cheap and easy to fit.

[Juular]

So I have checked and cleaned every reluctor ring. None were cracked and most were spotless. The driver's side front was quite rusty and the CV boot was torn so I just replaced the joint with a new one.

I also replaced all discs and pads and bled the brakes.

Finally I had the ABS module tested and some of the pins were resoldered.

Unfortunately none of this has helped, the fault still occurs at the same point.

I'm struggling to connect the fault with the function of the ebd pressure switch.. I mean the switch senses the fluid pressure in the reservoir, but the brake pedal is not involved whatsoever when the fault occurs?

[Juular]

Ok I've found it.

As you can see, wheel speeds are fine.



What I did notice whilst running live data during a drive is that the brake pressure switch value occasionally flicks between off and on.

It was hard to find as it works correctly at a standstill. Weird one!

These are discontinued parts now.. can I just install one with the same screw thread?

[Juular]

The saga is over. I found one from a scrap car.




No more abs light!

[aarongs]

I just wanted to say thanks Juular for posting all this.
My ABS and tracs off lights kept coming on whilst accelerating but nothing made sense. And I would not have known to look at this sensor and its wiring.

It was due in the garage for a proper scan when I read this thread.
Popped out to look at the wiring to this sensor as the pipe work below it has been replaced so a risk it was damaged. i discovered the plug was just not clipped in properly! So a really simple fix. No more lights coming on.