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Pelican Technical Article:

ABS Sensor Replacement

Jared Fenton

Time:

1 hour1 hr

Tab:

$30 to $150

Talent:

***

Tools:

5mm hex driver, penetrant oil, silicone grease, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

Jetta MkIV 2.0L (1998-05)

Parts Required:

ABS sensor

Hot Tip:

Spray the area beforehand with penetrant oil

Performance Gain:

ABS system works as it should

Complementary Modification:

Replace brake pads

The ABS wheel speed sensor on the Mk4 Jetta monitors road wheel movement and sends an electronic signal to the ABS module. This signal is used to calculate road wheel speed to help with ABS braking and stability control features. When an ABS wheel speed sensor fails, the ABS module loses road wheel speed for the corresponding wheel and sets a fault code for ABS wheel speed signal. When a fault code is set, the ABS warning light will illuminate. You will have to scan the module with a diagnostic scanner or code reader and read the fault codes to determine which speed sensor is the problem. Keep in mind that other problems can illuminate the ABS warning light. Be sure to scan and read fault codes before you start replacing expensive parts.

Sometimes, you get lucky and the sensor only needs to be cleaned as brake dust and dirt can sometimes affect the operation of the sensor. If you get a fault code and it points out a failure with a sensor, you may want to remove and clean it before buying a new one. If the fault code re-appears, you may have to replace it.

Begin by jacking up and supporting the front of the car on jack stands, after putting on those stylish safety glasses. For more info please see our article on Jacking up your Mk4 Jetta. Remove the front wheels and look directly behind the rotor at the top. You will see a wire harness leading into the back of the wheel hub. You'll see a 5mm hex bolt holding the sensor into the hub. Remove the screw.

Usually, removing the sensor from the hub can either be a simple matter of pulling it up and out of the hub. More often, the sensor will be stuck and will require some force to remove it. If the sensor is stuck, spray a good penetrant spray around the base and let it soak in for a few hours. Use a pair of pliers and gently walk the sensor back and forth to break it free. If it is still stuck, you can remove the brake rotor and gain better access to pry the sensor out with an appropriately sized screwdriver. Please see our articles on Rear Brake Pad Replacement and Rear Rotor Replacement for more information.

Once the sensor is removed, press the tab on the electrical connector and pull it off. Now clean the inside of the housing with brake cleaner. If there is any corrosion inside the bore, clean it off using a wire brush. You'll want to install the new sensors with a thin coating of anti-seize compound to the ABS sensor and the inside of the housing. It's also a good idea to put a drop of blue Loctite on the Allen bolts before re-installing them. All that's left is to plug the electrical connectors back in and you're done.

Front Sensor, Left and Right Sides: Shown here is the front ABS sensor (green arrow) on the Mk4 Jetta.
Figure 1

Front Sensor, Left and Right Sides: Shown here is the front ABS sensor (green arrow) on the Mk4 Jetta. Press the tab on the electrical connector (purple arrow) and pull it off.

Front Sensor, Left and Right Sides: Loosen and remove the 5mm hex bolt securing the ABS sensor to the wheel hub.
Figure 2

Front Sensor, Left and Right Sides: Loosen and remove the 5mm hex bolt securing the ABS sensor to the wheel hub.

Front Sensor, Left and Right Sides: Getting the sensor out of the wheel hub can sometimes be a real chore.
Figure 3

Front Sensor, Left and Right Sides: Getting the sensor out of the wheel hub can sometimes be a real chore. Use penetrant oil and walk the sensor back and forth as you withdraw it. When fitting the new sensor, it helps to coat the outside with a little silicone grease.

Front Sensor, Left and Right Sides: As you can see here, there's lots of corrosion buildup on the ABS sensor (green arrow).
Figure 4

Front Sensor, Left and Right Sides: As you can see here, there's lots of corrosion buildup on the ABS sensor (green arrow). Either clean the sensor thoroughly or replace it with a new one. 

Rear Sensor, Left and Right Sides: The rear sensors are pretty similar to the front, however the positioning is a little different.
Figure 5

Rear Sensor, Left and Right Sides: The rear sensors are pretty similar to the front, however the positioning is a little different. Press the tab on the electrical connector (green arrow) and pull the connector off.

Rear Sensor, Left and Right Sides: Like the front sensors, loosen and remove the 5mm hex bolt and pull the sensor out.
Figure 6

Rear Sensor, Left and Right Sides: Like the front sensors, loosen and remove the 5mm hex bolt and pull the sensor out. Replacement is the same as the front.


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