Most modern vehicles have some type of ABS, traction control, and/or electronic stability systems to provide for safe braking and handling in a variety of conditions. One of the primary inputs for these systems is the data from wheel speed sensors.
The main symptom of a problem with a wheel speed sensor is usually an ABS warning light, traction control or electronic stability system warning light. Usually, there is one speed sensor per wheel, reading the wheel speed from a tone ring that rotates with the axle.
Usually, they are fairly easy to replace, but sometimes the wheel and brake assemblies need to be removed before they can be accessed.
Wheel Speed Sensor Replacement Costs
On average, it costs about £135 to have a speed sensor replaced on most vehicles.
To illustrate the speed sensor replacement cost, some estimates on common vehicles using a £70 an hour labour rate are presented below:
- 2008 Volkswagen Jetta with a 2.5-liter engine — The labour time to replace a front or rear-wheel speed sensor is 0.3 of an hour. A factory wheel speed sensor costs about £70 on either end, and a non-factory replacement part costs about £10 on either end. This makes the job about £90 using OE parts and about £30 using aftermarket parts.
- A 2005 Kia Optima with a 2.4-liter engine — The labour time to replace a front or rear-wheel speed sensor is 0.6 of an hour. A factory wheel speed sensor costs about £125 for the front and about £145 for the rear. Standard replacement parts cost about £60 for the front and about £87 for the rear. This would make replacing the front sensor cost about £165 with OE parts and about £100 with aftermarket parts. Replacing a rear speed sensor would be about £185 using OE parts and about £130 using aftermarket parts.
- 2004 Honda CR-V with a 2.4-liter engine — The labour time to replace a wheel speed sensor is 0.5 of an hour for the front and 0.4 of an hour for the rear. A factory wheel speed sensor costs about £200 on either end, and a non-OE replacement sensor costs about £68 for the front and about £55 for the rear. The total cost for replacing a front sensor is about £235 using OE parts and about £100 using aftermarket parts. Replacing a rear sensor would cost around £228 using OE parts and around £83 using aftermarket parts.
- 2007 Chevrolet 1500 with 4WD 5.3-liter engine – It would take 0.9 of an hour of labour for the front and 0.4 of an hour for the rear. A factory wheel speed sensor costs about £160 for the front and about £60 for the rear. On the other hand, an aftermarket replacement sensor costs about £24 for the front and about £43 for the rear. The total cost of replacing a front sensor would be about £225 using OE sensors and about £87 using aftermarket parts. Replacing a rear-wheel speed sensor would be about £88 using OE parts and about £70 using aftermarket parts.
Saving costs on a wheel speed sensor is probably limited to just making sure that the diagnosis is accurate. In most cases, a sensor problem will trigger a code and turn on the ABS light on the dash. Diagnosis of a speed sensor code is usually pretty straightforward, though it isn’t always, and it is customary to have a one-hour diagnostic charge tacked on to the bill.
There is also a good case to be made for using OE wheel speed sensors, as the exact clip placements and routing provisions are critical to the sensors being reliable, the air gap to the tone ring has to be exact, and the sensitivity of the sensor relies on very tight electrical specifications. Repairing speed sensor wiring is also usually not a good idea.
What Can Go Wrong with a Wheel Speed Sensor?
The sensor itself uses a magnetic field that fluctuates as a toothed metal ring moves through it, creating a small electrical signal from which rotating speed can be directly inferred.
One thing that can go wrong is that, in some designs where the toothed ring is exposed to the elements, debris can build up in the toothed ring (including metal particles attracted to the magnet) and create an unclear signal. A sensor and ring that have debris built up can be cleaned and checked for damage, and then re-tested to see if the operation is normal.
In other designs where the toothed ring is an internal part of a wheel bearing assembly, a problem in the bearing can change the distance between the sensor and the toothed ring, which also causes signal loss. In that case, the bearing and sensor are usually replaced as an assembly. Most wheel bearing assemblies of this type come with a new wheel speed sensor installed.
Another more common problem is the wiring. Most wheel speed sensors come with a length of wiring permanently attached, which is carefully routed and clipped along its path from the wheel hub and through the suspension to a connector in the wheel well.
A minor routing problem can cause a wire to rub through on a metal part or a tyre or pull apart during steering. The sensor signal is a low-voltage frequency modulation. Wiring repairs inevitably introduce resistance that can interfere with that, so wiring repairs are usually not recommended. Usually, a sensor with damaged wiring will need to be replaced.
In most cases, it takes about an hour, even including diagnostic time.
The ABS won’t work. Most of the time, a sensor failure will trigger the ABS light, and the ABS won’t function as long as it detects a fault in the system.
The most common other problem is a wheel bearing issue. The sensor relies on an exact air-gap spacing for a toothed ring in the bearing, and any wear or debris in that area can interfere with the signal.