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This is a 5 WIRE grounding kit walkthrough (REV 2.0)

Mazda3 2.3L  (2004-2008) Hatchback and Sedan

Install time: 15-30 minutes

Note: This kit will fit ALL mazda3's that have a 2.0L engine or 2.3L engine.

For 2.0L engine "i" model mazda3s, Connection Point "E" will be slightly different.  The mount for the engine cover screws off and underneath is a stud that the mount screws too. Connect your ground wires there and screw the mount back on (its attached to a nut that screws into that stud).


8mm and 10mm socket wrench


An extension bar will help make removing the bolts easier


Some tape to protect the ring terminals so you don't short your battery.  (connect positive to negative on accident)


A magnet will help prevent you from dropping nuts or bolts into the engine


Grounding Wires with the right size ring terminals on the ends

You will begin by popping the hood and removing the engine cover.  Just lift it vertically and it will release at the red circled areas.  These are the points of contact the cover has with the engine.
Then remove the battery cover next.  There are tabs circled in blue.  The three tabs closest to the front of the car need to be unlocked first.  Then once you can lift the front of the battery cover up, just pull it towards the front of the car.

Remove the battery vent.  To do this you can use your finger nail or a Phillips screw driver to help remove a plastic pin located near the front left head light.

The battery vent should lift right out of the car once this one pin is removed.  Note that there's a small arrow that marks the center of the battery cover vent intake.   This is to help you put the vent back in.  If you can't find the arrow then no big deal, there's only one way to put the battery vent back in.

First sort the wires from smallest to largest.  The smallest wire will be WIRE 1, and the longest wire will be WIRE 5:

Note that the smallest wire has terminals not facing up.  This is on purpose for a cleaner install.  I've positioned the connectors to perfection on every wire for the cleanest possible install.  Also notice that the two longest wires have smaller ring terminals on the end.  These two small ring terminals connect to the negative battery terminal.

The installation will begin with the smallest wire, and end with the two longest wires.


TIP: Use a magnet so you don't drop any nuts or bolts when unscrewing.

If you don't have a magnet handy you can just shove a towel around the work area so the nut has no where to fall.

Also if working on a HOT engine bay, the bolts will be hot to touch.

SAFETY TIP:  BEFORE working on your car any further, you may want to DISCONNECT your negative battery terminal.  This is to prevent any electrical shorts while working in the engine bay.  When I do this, I like to WRAP the negative battery clamp in a thick towel so that they don't come into contact with the negative battery terminal on accident.

For my installation I did not do this because I did not want to reset my ECU.  IF you reset your ECU, your engine will have to re-map and learn its idle and set air/fuel ratios again.  This causes erratic engine behavior and rough idling.  I wanted to FEEL the difference the grounding kit made, not feel the ECU re-learning.  :)

So now begins the installation.  Use a 10MM socket on NUT "A" and bolt "B".  You may not want to tighten any bolts or nuts all the way until all 5 wires are installed.  This way you can reposition the wires so they're routed the right way.  This also makes it convenient if you've put a wire in the wrong place and have to redo a wire.

For your second smallest wire (Wire 2), you are going to connect it to bolt B and fuel rail bolt "C".  Now there are two wires connected at point "B".

TIP:  Bend the ring terminal connecting to bolt "C" like the image below for a cleaner installation.

The image on the left shows how the smallest two wires will look after being installed.

These wires contain a highly durable sleeve that is resistant to abrasion so feel free to route them however you want.  It is OK for these wires to touch the edges of plastics.

A word of Caution:  Do not put these wires on a metal part that gets really hot.  (Such as the exhaust manifold)

Unscrew bolt "E".

Point "E" is located on a bronze looking plate attached to the engine block.  There are going to be TWO wires connecting to point: Wire 3, and Wire 4.

When you connect Wire 4, make sure you are connecting the end of the wire that has the large sized ring terminal.  The smaller sized terminal will connect to the negative battery.

Next, connect the other end of Wire 3 to the left fuel rail bolt "D".  (Bend the terminal so it fits cleanly like you did with the other fuel rail connection)


In order to safely route the wires through the inside panel of the battery box, you should wrap the ends with tape so that you don't accidentally touch ANY part of the positive battery terminal.  Even with tape on the terminals, stay away from shorting the battery!

View the thumbnail below to route Wires 4 and 5 through the SIDE hole and NOT the hole facing the front of the car.  There are MULTIPLE large holes existing in the battery box.  If you absolutely can not figure out a way to make these two LONGEST wires fit you most likely put the wires through the wrong hole in the battery box.  If you know for certain there's no hole on the side of the battery box, then you'll have to improvise and make your own hole.

  This image on the left shows how to route the taped wires successfully.

Below shows the installation of Wires 3 thru 5.

bulletWire 3 connects the engine grounding point "E" to the driver side fuel rail "D"
bulletWire 4 connects the engine grounding point "E" to the negative battery terminal "G"
bulletWire 5 connects the throttle body "F" to the negative battery terminal "G"

NOTE:  Wire 5 can connect to the throttle body in ANY of the bolts holding it in place.

Pictured below shows how wire 4 is going to go through the SIDE of the battery box to the negative terminal.

In the next step you will remove and install the small nut for the negative battery terminal.  Please be careful and don't connect the positive and negative battery terminals accidentally with a solid metal wrench. I used a rubber handled socket wrench and no extension bar.  You may also use gloves to do this.
Pictured below is the connection to the negative battery terminal.  I put the ring terminals on different sides of the battery clamp and then tightened the nut with a socket wrench and NO extension.  If you accidentally disconnect the negative battery terminal, then you may reset your ECU and lose your radio station presets.

If you do reset your ECU, don't blame the grounding wires for the way your engine behaves after firing it up...

After this final connection point "G" - negative battery terminal, check and tighten all the nuts and bolts of every letter snug and firm.  Do not OVERTIGHTEN.  Aluminum threads are SOFT and strip easily.  Make sure the wires are routed neatly and won't get in the way of anything.

Give the negative battery terminal a tug left and right to see if you've properly secured it.

Reset your ECU if you want.  Or don't do it to see if you'll notice the improvement!

Reinstall the battery vent, battery cover and engine cover.  Take your car for a test drive.

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Last modified: 03/24/10