Car Door Lock Relay Replacement

[mechanics911]

How to Replace a Door Lock Relay
Electric door locks work via a door lock relay located near the brake pedal, behind the stereo, behind the passenger air bag, or under the hood.

A relay is an electromagnetic switch operated by a relatively small electric current that can turn a much larger electric current on or off. The heart of a relay is an electromagnet (a coil of wire that becomes a temporary magnet when electricity flows through it). You can think of a relay as a kind of electric lever: switch it on with a tiny current and it switches on (“leverages”) another appliance using a much bigger current.

As the name suggests, many relays are incredibly sensitive pieces of electronic equipment and produce only small electric currents. But often we need them to operate bigger pieces of apparatus that use bigger currents. Relays bridge the gap, making it possible for small currents to activate larger ones. That means relays can work either as switches (turning things on and off) or as amplifiers (converting small currents into larger ones).

When power flows through the first circuit, it activates the electromagnet, generating a magnetic field that attracts a contact and activates the second circuit. When the power is switched off, a spring pulls the contact back up to its original position, switching the second circuit off again. The input circuit is switched off and no current flows through it until something (either a sensor or a switch closing) turns it on. The output circuit is also switched off.


A door lock relay can be located in four different places on a vehicle, including:

Under the dash on the wall by the brake pedal
Under the dash in the middle of the cab behind the stereo
Under the dash behind the passenger air bag
In the engine compartment on the firewall on the passenger side
It is a sign of door lock relay failure when you’re trying to operate the door lock switches on the door panel and the door locks will not activate. Commonly the computer will override the relay circuit when using a keyless remote access to the locks, routing the power through the alarm system provided that the vehicle is equipped with an alarm of some sort. A key can still manually unlock the doors.

Some computer codes that may be displayed for a failed door lock relay include:

B1300
B1301
B1309
B1310
B1311
B1341
B1392
B1393
B1394
B1395
B1396
B1397
The following step-by-step guide will walk you through replacing this part in the event that it fails.

Part 1 of 3: Preparing to replace the door lock relay

Having all of the necessary tools and materials prior to starting the work will allow you to get the job done more efficiently.

Materials Needed

Allen wrench set
Boxed end wrenches
Cross tip, or phillips head, screwdriver
Disposable gloves
Electrical cleaner
Flat tip screwdriver
Needle nose pliers
New door lock relay
Nine-volt battery saver
Ratchet with metric and standard sockets
Torques bit set
Wheel chocks
Step 1: Position the vehicle. Park your vehicle on a flat, hard surface. Make sure that the transmission is in park.

Step 2: Secure the vehicle. Place wheel chocks around the tires. Engage the parking brake to the lock the rear tires and keep them from moving.

Step 3: Install a nine-volt battery saver. Plug the battery saver into your cigarette lighter.

This will keep your computer live and keep your settings current in the vehicle. If you do not have a nine volt battery saver, though, that’s okay.

Step 4: Open the hood and disconnect the battery. Remove the negative post from the battery terminal. This disconnects the power to the door lock relay.

Part 2 of 3: Replacing the door lock relay
For those located under the dash by the brake pedal:

Step 1: Find the door lock relay. Go to the breaker panel on the wall next to the brake pedal. Using a diagram, locate the door lock relay.

Step 2: Remove the old door lock relay. With a pair of needle nose pliers, pull out the relay.