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Audi A4 Brake Pressure Sensor Replacement
 
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Pelican Technical Article:

Audi A4 Brake Pressure Sensor Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$40 to $80

Talent:

*

Tools:

Audi scan tool, Philips head screwdriver, 23mm deep

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New brake pressure sensor, brake fluid

Hot Tip:

Be prepared to catch the brake fluid

Performance Gain:

Working brake system

Complementary Modification:

Bleed the brakes

The braking system on the Audi A4 uses a series of sensors to monitor and control the ABS system. Failure of the sensors can lead to problems with the system and unsafe braking. If you are getting an error code for the brake pressure sensor, you should replace it right way.

Replacing the sensor is not difficult, but you will be opening the system and introducing air into it. This means that you will have to completely bleed the braking system, including having the Audi scan tool to place the ABS control module into bleed mode. It is not safe to bleed the system without this tool, as the sensor is attached to the ABS control module. When you open the system, you will be introducing air into the module itself.

Do NOT attempt to perform this work without being prepared to properly and safely bleed the system afterwards.

The brake pressure sensor mounts in the ABS control unit.
Figure 1

The brake pressure sensor mounts in the ABS control unit. The control unit (green arrow) is located between the coolant overflow reservoir (red arrow) and the windshield washer reservoir (yellow arrow).

You will need to remove the coolant overflow reservoir (red arrow) to access the brake pressure sensor, but you do NOT need to drain the coolant to do this.
Figure 2

You will need to remove the coolant overflow reservoir (red arrow) to access the brake pressure sensor, but you do NOT need to drain the coolant to do this. Use a Philips head screwdriver and remove the single screw on the front of the reservoir (yellow arrow). Slip the reservoir forward and out from the two mounting points on the rear (green arrow). If you need additional assistance please see our article on coolant overflow reservoir replacement.

With the reservoir removed, you can see the sensor (red arrow).
Figure 3

With the reservoir removed, you can see the sensor (red arrow).

Disconnect the wiring connection (red arrow) by squeezing the tabs on the end and then pulling it straight off the sensor (yellow arrow).
Figure 4

Disconnect the wiring connection (red arrow) by squeezing the tabs on the end and then pulling it straight off the sensor (yellow arrow).

Use a 23mm deep socket to fit over the end of the sensor (red arrow) and remove the sensor.
Figure 5

Use a 23mm deep socket to fit over the end of the sensor (red arrow) and remove the sensor. While you may be able to use some other wrench or pliers to get the sensor off, it is a very tight fit between the brake lines. You will need to torque the sensor down to the correct value when reinstalling, so make sure you use the right tool.

This photo illustrates how the brake fluid will drip out from the ABS control unit (red arrow) so be prepared to catch it.
Figure 6

This photo illustrates how the brake fluid will drip out from the ABS control unit (red arrow) so be prepared to catch it. Even if you are quick replacing the sensor and not much fluid drips out, you still will have allowed air to enter the system and MUST bleed the brakes.

When installing the new sensor, never place any type of Teflon tape or sealing compound on the threads of the sensor.
Figure 7

When installing the new sensor, never place any type of Teflon tape or sealing compound on the threads of the sensor. Installation is the reverse of removal. Even though I said it before, it bears repeating. You must bleed the brake system using the Audi scan tool.

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Comments and Suggestions:
JACK Comments: THANK U FOR THE WANDERFUL INFORMATION MATE
April 11, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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