After I did a front wheel bearing change on my 2000 Ford Taurus SE wagon, the ABS light on my dash lit. It showed a C1 233 code: “Left front wheel speed sensor input signal missing”. I replaced the sensor and the ABS light went out. After driving for 30 miles, and the ABS light lit again.
I am getting the same code as before - input signal missing for the left front wheel. I drove the car with live data on the scanner and saw where the other three wheels reported 30 MPH speed, the left front was reporting 2 to 4 MPH. The replacement sensor was manufactured by Dorman. Would OEM be better for this application? Or could the sensor be fine, and something else be causing this issue?
The wheel speed sensor began working again - I do not know why - it was nothing I did. With the sensor working, the ABS light remained on - which was odd because when I first installed the sensor, the ABS light went out immediately. I used the scanner to clear the ABS “no signal from the front left wheel” fault code because it clearly was now sending data.
After I cleared the code, the ABS light went out, which was good. But now the ABS system is activating the left front caliper at every stop. Not good. I guess I could try another sensor.
Did you clean the surface where the speed sensor mounts of any rust/dirt, and then apply a thin coat of grease to that surface before installing the new sensor?
I am going to uninstall it and clean the installation area. The previous sensor broke off in the opening in the steering knuckle. I spent most of my time extracting that piece of the sensor. I did use a dremel sandpaper drum to clean out the opening in which the sensor inserts, but did not do much to clean up the mounting surface. The connection seemed clean and tight. Someone advised me OEM is the most reliable option when it comes to wheel speed sensors, so if the clean-up and connection do not work, I might be looking at swapping sensors.
The wheel bearing is a new Moog unit with about 50 miles on it. When I installed it, I torqued the axle nut down to the specified torque value, which is supposed to help ensure the maximum life for the wheel bearing. I guess there is always the possibility that I got a bad wheel bearing out of the box.
I decided to get an OEM sensor. The left side sensor has been discontinued by Ford, so I ordered a new-old-stock Motorcraft sensor from an E-Bay seller. Auto parts stores had sensors for sedans, but not wagons, and this car is a wagon.
I went back and checked the Dorman sensor installation. It is sitting on clean metal and is flush with the knuckle. When I pulled it, I wiped it down to ensure it was clean. It did not fix the problem.
I changed front bearings and sensors in the last 2 yrs. did rotors this weekend and saw 1 wire is broke clean. I thought China at least knew how to make wire? Yes the abs light came within 6months of new bearings. Was nice to have it off for awhile.
Your “new” aftermarket sensor may be faulty… replacement one may be faulty again…
See here for the similar disaster:
Essentially: sensor was replaced 2 or 3 times only to discover that yet another aftermarket sensor is not conforming to the specs, OEM sensor immediately cured the issue.
I chaanged my daughters sensor on her CRV with aftermarket. Light came back on. Check for signal at sensor side with good signal. Checked for signal at other side of connector with signal. I had no signal at module. replaced wiring from connector to module. It worked for a few days and faulted again. This time when checking for signal at module there was no signal until I jiggled the connector. So i repaired connector and problem solved after kicking myself for doing all this over an intermittent connector problem. Coinsidently, the next ABS light I worked on from a different car had the same problem, but this time I made sure to check the connector first. All that to say it’s a good idea to jiggle test the connector before you get too involved.
Thanks everyone for relating your experiences with sensors and sharing the video. A mechanic who does a radio/podcast show that I listen to from time to time has a philosophy about parts that goes something like “new stands for never ever worked”. His advice is to keep in mind that even a new part can be defective right out of the box.
The connector looked good when I installed the Dorman sensor, and it must have been good for at least 30 miles. When I get the new old stock OEM sensor I will take a closer look at the connections.
The frustrating part to all of this is that I am getting a signal out of the left front sensor. Below are two frame grabs from my scanner. The first one is without the brakes being applies, the second is with the brakes being applied. When the brakes are applied you can see only the left front inlet valve has a value of “ON”, the other three oar “OFF”.
Someone earlier mentioned that a weak sensor signal can cause problems. I am hoping the scanner data means the sensor is working, but not working well enough for the system to work correctly.
Brakes not applied
ABS Pump Motor Relay OFF
ABS Valve Control Relay ON
Brake ON/OFF OFF
Continuous Codes 0
Left Front Inlet Valve State OFF
Left Front Outlet Valve State OFF
Left Rear Inlet Valve State OFF
Left Rear Outlet Valve State OFF Left front wheel speed sensor 21.13 mph Left rear wheel speed sensor 21.13 mph
Right Front Inlet Valve State OFF
Right Front Outlet Valve State OFF
Right Rear Inlet Valve State OFF
Right Rear Outlet Valve State OFF Right front wheel speed sensor 21.13 Right rear Wheel Speed Sensor 21.13
(WSS)
Brakes being applied
ABS Pump Motor Relay ON
ABS Valve Control Relay ON
Brake ON/OFF ON
Continuous Codes 0 Left Front Inlet Valve State ON
Left Front Outlet Valve State OFF
Left Rear Inlet Valve State OFF
Left Rear Outlet Valve State OFF Left front wheel speed sensor 9.94 mph Left rear wheel speed sensor 9.32 mph
Right Front Inlet Valve State OFF
Right Front Outlet Valve State OFF
Right Rear Inlet Valve State OFF
Right Rear Outlet Valve State OFF Right front wheel speed sensor 6.84 Right rear Wheel Speed Sensor 5.59
(WSS)
I replaced the Dorman sensor with a Motorcraft sensor. I still have the same issue. I did scan again and came up with code: “C1266 - ABS valve relay/valve relay supply voltage fault”. Since live data on the scanner shows the sensor is working, I will use the fault code as a staring point and start looking for problems with power to the ABS unit.
