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Audi A4 Crankshaft Positioning Sensor Replacement
 
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Pelican Technical Article:

Audi A4 Crankshaft Positioning Sensor Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$35

Talent:

*

Tools:

10mm Allen, universal joint and extensions

Applicable Models:

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

Parts Required:

New CPS

Hot Tip:

Use a mirror

Performance Gain:

Smoother running car

Complementary Modification:

Replace Camshaft positioning sensor

Modern cars use a very complex system of sensors to pass smog requirements and achieve the MPG's that they do. All of these sensors transmit data to a central computer that determines the amount and temperature of the air entering the engine, the placement of the valve train in relation to the crankshaft, the amount of fuel distributed to each cylinder along with the timing and duration of the spark. The sensor that will be covered in this article is the crankshaft positioning sensor, which is also referred to as the engine speed sensor. If the crankshaft position sensor is not operating properly, your car will run very erratically or perhaps not at all.

Your fuel injection computer (DME) may output a code that indicates a faulty crankshaft position sensor (CPS or engine speed sensor RPM). This important sensor tells the car's computer where the flywheel is located in relation to the combustion cycle. The DME takes the signals from both the cam position sensor and crankshaft position sensor and calculates when to fire the fuel injectors and spark plugs.

To replace the sensor you will need to safely raise and support the vehicle as well as remove the under body trays.

Begin by safely raising and supporting the vehicle and removing the under body engine tray. Please see our articles on jacking up and supporting your vehicle as well as removing the under body trays.

The CPS sensor is relatively easy to remove but very difficult to photograph while in the motor.
Figure 1

The CPS sensor is relatively easy to remove but very difficult to photograph while in the motor. The connection for the CPS or engine speed sensor is located behind the over flow reservoir (red arrow). You can move the reservoir out of the way without removing the fluid if you are careful; if you are worried take a turkey baster or fluid pump and remove a little fluid. Next, use a Philips head screwdriver and remove the single screw on the front of the reservoir (yellow arrow). The reservoir sits in two brackets on the rear but you can lift it up and move it forward to remove it from the brackets.

The CPS or engine speed sensor connection is directly under the reservoir brackets and is the gray connection (red arrow).
Figure 2

The CPS or engine speed sensor connection is directly under the reservoir brackets and is the gray connection (red arrow). Slip it out from the plastic mount and separate the connection. The cable is long and does not run straight to the sensor, which is located beside the oil filter. You will need to follow the path of the cable and clip the series of zip ties.

You will need to remove the under body tray (red, yellow and green arrows).
Figure 3

You will need to remove the under body tray (red, yellow and green arrows). If you need additional assistance with this please see our article on under body tray removal.

The sensor is located on the block (red arrow) just behind the oil filter.
Figure 4

The sensor is located on the block (red arrow) just behind the oil filter. Reach up with your 10mm Allen and remove the single bolt and pull the sensor from the block.

Here is a picture of the sensor.
Figure 5

Here is a picture of the sensor. You can see where the single bolt goes through to attach the sensor to the engine (red arrow) making it impossible to install the senor other than one way. Make sure to route the cable back up to the connection. It does not need to take the exact same route as from the factory. What is of utmost importance is to make sure it is safe and zip tied off where needed. Installation is the reverse of removal.

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