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Matt, Engineer
Category: UK Ford
Satisfied Customers: 22001
Experience:  BEng hons Mech engineering, in auto industry 23 years
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Focus: wheel bearing..I have had the ABS warning light..seal..pulling

Customer Question

After renewing the wheel bearing on my Focus I have had the ABS warning light permanently illuminated and fault code C1233 (No input from Front LH wheel sensor). I have since put another wheel bearing in using a press with the orange seal facing the sensor and have also renewed the wheel sensor. Now pulling my hair out as MOT due in July.
Submitted: 6 years ago.
Category: UK Ford
Expert:  Matt replied 6 years ago.

I'd 1st check that the sensor is pointing at the toothed wheel on teh bearing / axle

remove the sensor and look down the hole as square to the hole axis as you can

you shoudl be able to see the square teeth bang in the middle of the hole

If this is out of position then the sensor won't work

If this is OK then I'd trace back along the speed sensor wire to locate the where it plugs into the hydraulic pump / modulator under the bonnet

and test for continuity between here and the sensor plug int he wheelarch

if you spin the wheel and measure for AC volts you should get a signal that increases with rpm
also worth giving all the contacts a good squirt of switch cleaner ( not WD40)
Customer: replied 6 years ago.
There is a bit of confusion regarding my car. There are no teeth on the drive shaft and I believe that the sensor picks up the signal from the magnetic strip in the wheel bearing, hence the orange seal facing towards the sensor. I have disconnected the ABS sensor cable at the wheel arch and checked for continuity at the fuse box, all seemed OK.

Expert:  Matt replied 6 years ago.
Hello Paul

have you tried the AC volt meter trick to see if the sensor is outputting anything?

Customer: replied 6 years ago.
Yes have already tried that and have done a continuity test from the ABS terminal (where the sensor plugs into) to the fuse box.


Expert:  Matt replied 6 years ago.

if the wheel sensor is working OK and the wire connection is good up to the fusebox then its possibly a fault with the ABS control unit under the bonnet

You've done as much as you can so far so unfortunatly the next step is to send the unit off for testing

I've used this firm in the past