ABS Light Intermittent

[horhif]

hi

the ABS light is coming on intermittentky on my Focus 1.8 TDCi 2005.

When the light is OFF, and i brake, it's like the ABS is engaged i.e. you get the pushing back from the brake pedal

When the light is ON, when applying the brake, everything seems normal.

i just hooked up ForScan as recommended by some of the users on here, and i get this reading:

DTCS in ABS: C1142-A0

 

putting that in Google seems to suggest "C1142 wheel Speed Sensor RF Tone Ring Tooth Missing Fault"

 

any ideas on what wheel this would be?  and if i take the wheel off, what am i looking for exactly? i.e. is it something i could check is loose etc?

 

thanks!
 

[FatHead1979]

ABS system/ECU needs a constant accurate flow of speed measurements to be able to work properly.  If just 1 of the sensors (1 for each corner of the car) starts to act up it can cause all sorts of undesirable ABS behaviour.

The sensors are pretty cheap but bear in mind sometimes the sensor can be OK and it could be the wiring to and from the sensor that's at fault.  Have you tried using Forscan to record the reported speeds from the ABS/speed sensors, if one sensor is not reporting a consistently as the others than you'd have your starting point for investigation.

[Micro]

RF would be the o/s/f wheel sensor?

Check the wiring to it, I believe they're in the actual hub though rather than a separate sensor.

[horhif]

On 1/2/2018 at 11:57 AM, 1979Damian said:

ABS system/ECU needs a constant accurate flow of speed measurements to be able to work properly.  If just 1 of the sensors (1 for each corner of the car) starts to act up it can cause all sorts of undesirable ABS behaviour.

The sensors are pretty cheap but bear in mind sometimes the sensor can be OK and it could be the wiring to and from the sensor that's at fault.  Have you tried using Forscan to record the reported speeds from the ABS/speed sensors, if one sensor is not reporting a consistently as the others than you'd have your starting point for investigation.

hi,

i'v tried what you suggest with recording the speed in Forscan.

 

so as it looks, the front right sensor is the issue.

i have taken the wheel off, cleaned the sensor and used can of air to blow out dirt etc.  also checked the wiring and it seems fine.

can you advise on the next logical step please?

 

would you buy a new sensor or is it possible to swap sensors, re-run the check and then you could see if the original sensor is broken etc?

 

thanks for all your advice and the other posts from others!

[Micro]

If you wiggle the wiring does it affect the signal? 

[FatHead1979]

Wow, it's no wonder the ABS has been kicking in all the time.

I'd suggest swapping the 2 front ones around and see if the problem moves to the other corner of your car, if it does then you know it's a nice simple case of replacing 1 ABS sensor.  If it doesn't move then you can rule out the sensor and probably need to start looking at the wiring etc.

[horhif]

On 1/7/2018 at 3:53 PM, 1979Damian said:

Wow, it's no wonder the ABS has been kicking in all the time.

I'd suggest swapping the 2 front ones around and see if the problem moves to the other corner of your car, if it does then you know it's a nice simple case of replacing 1 ABS sensor.  If it doesn't move then you can rule out the sensor and probably need to start looking at the wiring etc.

so....i've finally got changing the sensors around.....and to be honest, its turning into an episode of Fawlty Towers lol

while taking the wheels off, 2 nuts rounded........i've been able to get them off by hammering a smaller sizer socket onto them.  Then the locking nut socket, the inside of it, snapped......and i'd to take the car to the garage to get these removed.  I got all 4 removed from the car.....just going back to normal nuts....just glad this never happened at the side of a road.

So now i've changed the sensors over, drivers to passenger, and vice versa. (The drivers side (right side) was the one giving the error on Forscan originally.)

Now here's what i have:

(OK) [12:56:52.037] Found module:  ABS - Anti-Lock Brake / Traction Control Module
(WARN) [12:56:52.135] DTCs in ABS: C1155-A0, C1142-A0

Previously i'd only the C1142-AO error.

So on ForScan, it says that "C1145 - Left front wheel sensor input circuit failure" but if you Google C1145 it says its an error with the right front wheel.

Anyhow.......here is the new scan, still showing an error with the right front.

I've inspected the cable, tried moving it etc. and can see no damage or problems (as per suggestion above)

Getting to the stage i think i need to leave this into the garage.

PS......on another note, my rear brake light is working intermittently.  Checked the bulb, bulb holder, and cabling and look fine.  ForScan showed this.....U0140....malfunction indicator lamp....would this be showing it up in ForScan?

anyhow thanks for your help!

[hutsi]

wheel bearing