Mercedes-Benz E-Class and E-Class AMG: Why Does My Alarm Keep Going Off?

Gain control over an unpredictable vehicle alarm using these incredible DIY tips.

By Charlie Gaston - May 4, 2015

This article applies to the Mercedes-Benz E-Class and E-Class AMG (2002-2009).

No one likes a noisy neighbor. If the alarm on your Mercedes-Benz E-Class goes off intermittently, the truth is there are a number of likely culprits. The problem is fixable, but you'll need to cover the bases before pushing up your sleeves and doing some of the more complex repair work. This DIY project won't tie up a lot of your time, but you will need to purchase a few materials and/or replacement parts. Read more to get started!

Materials Needed

  • Replacement battery
  • Used or new PSE pump
  • Flat head screwdriver
  • Pliers
  • Socket wrench

Step 1 – Replace the battery

It might be on its last leg.

Low voltage could be the culprit here. If your vehicle alarm goes off intermittently, check the battery. It could be defective or on its last leg. The voltage should read around 14 volts if the battery is in good shape.

  • To test the battery for proper voltage levels, use a voltmeter.
  • Used voltmeters are available online for $50 and up.
  • Check that the voltage on the new battery is correct before installing.
  • Properly dispose of the old battery.
Figure 1. Checking battery voltage.

Step 2 – Check the Pneumatic System Equipment (PSE) pump

It might be malfunctioning.

The PSE pump performs a number of functions, including, but not limited to, the locking and unlocking of your driver side and passenger side doors, as well as the releasing of your trunk striker and the extending and the retracting of your trunk handle when opening the trunk door.

  • The pump sits inside the trunk well.
  • It could become wet from rain, causing your alarm to go off intermittently. Overheating is also common.
  • You have two main options here: you could either replace the motor or replace the entire pump, depending on the severity of the damage.
  • If the motor has burned out, then you'll need to replace it.
  • Used pumps are available online.
  • It is perfectly fine to use the motor out of a used PSE pump, as long as it is in good working condition.
Figure 2. Mercedes-Benz PSE pump.

Pro Tip

Driving in heavy rains or using a pressurized water hose to clean your E-Class could force water into the pump, worsening the problem.

Step 3 – Remove the siren for a short-term fix

This is the cheapest solution, if you cannot afford replacement parts at this time.

The siren speaker is located behind either the front driver or passenger side wheel. While you do not need to jack up your vehicle, you will need to turn the wheel in order to remove the splash guard.

  • To access the siren speaker, unbolt the screws and nuts that hold the splash guard panel in place.
  • Once the speaker is visible, remove the bracket holding it in place.
  • Next, squeeze the wire clip from the siren and remove the siren by hand (it should fall directly into your hands once the bracket is removed).
  • By removing the siren speaker, you are leaving your vehicle vulnerable to theft.
Figure 3. Siren location.

Pro Tip

Cover and store the speaker in a dry, open location.

Step 4 – Visit a Mercedes-Benz service center

Your alarm might need professional repair, or the sensor could be damaged.

Depending on the age and health of your alarm system, a more complex electrical problem could be the culprit.

  • For faster service, make an appointment.
  • Let the technician know whether a specific action trips the alarm.
Figure 4. Mercedes-Benz service center.

Pro Tip

If your vehicle is still under warranty, the Mercedes-Benz dealership will replace the defective sensor at no cost to you.

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