2006 - 2013 Toyota Highlander Hybrid Plug-and-Play Car Harness Installation Instructions

Note: These instructions are for the new plug-and-play Prolong™ Car Harness.  If you have the older non plug-and-play version, click here for instructions.

(Click on below image

for larger photo)

Time Required: Approx 1.5-2 hours

Tools Required:
Trim panel removal tool
8mm, 10mm, 12mm, 14mm sockets
#0 flat head screwdriver
#2 phillips screwdriver

Recommended: Electrical safety gloves, Volt meter
Magnetic pickup tool

1) Fold 3rd row seat down (if equipped).

Using trim panel removal tool, remove the Rear Center Cargo Cover by unclipping five clips and removing two 12mm bolts

2) Remove four cargo net anchors.

Remove rear tail light covers

3) Remove cargo area side carpet panels.

Remove two clips and remove center cargo under tray.

Unclip and remove center fabric piece.

4) Remove the two upholstery clips and remove the rear lift gate trunk sill trim.

Remove the left & right side cargo cubbies by removing the 10mm finger nuts and lifting out of the vehicle.

5) Remove four 10mm nuts and remove the third seat upper crossbar (if equipped).

(if equipped with third row seat, otherwise skip this step)

6) Remove the third row seat belt latch buckles from the third row seat.

Remove the four 14mm bolts holding the third row seat in place.

Remove the third row seat through the rear of vehicle.

7) Remove the left side step trim.  

Repeat on right side of vehicle.

8) On bottom left side of second row seat, remove the hybrid battery disconnect cover.

Remove the orange hybrid battery disconnect.

9) Locate the three hybrid battery cooling intakes at the bottom of the second row seat.  Open battery intake screws covers as shown and remove the two screws per cover (six screws total).

Remove front seat rail trim pieces.

10) Remove the three hybrid battery cooling intake covers.


Clean the three hybrid battery cooling intake covers to remove any lint buildup.  Lint limits airflow across the battery cells and contributes to premature cell failure.

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11) Remove the four front 14mm mount bolts from the second row seat.

12) Fold second row seats down and slide forward as far as possible.

Remove the rear outer side trim pieces from both sides of the second row seat rails.

13) Remove the four rear seat rail mount covers from second row seat.
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14) Remove the rear six 14mm mount bolts from the second row seat.

15) Remove second row seats through the back of the vehicle.  They are heavy!  We recommend using a helper for this step.

16) Remove the rear side panels.  There are six 10mm screws and one clip on each side.  The left side 12V Aux socket must be unplugged.  The right side rear heater controls (if equipped) must be unplugged.

Remove the rear side panels through the back of the vehicle.

17) Remove the three carpet clips as shown.

Remove 14mm bolt and remove second row center seat belt latch anchor bracket.

18) Fold the rear carpet up and forward to expose the battery compartment as shown.

19) Remove the three hybrid battery exhaust duct covers from the vehicle.
20) Remove the three battery duct inlet brackets.  Each inlet bracket is held in place with two 10mm bolts.

21) Remove orange battery access clip.  Using orange battery disconnect, rotate 90 degrees counter clockwise to release clip as shown.

Remove two 10mm bolts holding battery disconnect cover on.  Remove cover.

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22) You are now dealing with exposed high voltage module terminals. Do not touch the terminals unless specifically advised by these instructions. Never touch more than one terminal at a time. Be very careful working around the semi-live battery! It can kill you if you do not respect it!

23) Remove the 10mm bracket bolt indicated.  Detach sensor wire bracket from battery cover.

24) Remove hybrid battery cover by removing:

  • One orange safety clip
  • Six 10mm nuts
  • Seventeen 10mm bolts
  • Eleven 12mm bolts
25) This is what it will look like with the battery cover removed.

26) We highly recommend taking a few extra minutes to clean the three hybrid battery cooling fans. The fan has no filter and often becomes clogged with debris. This contributes heavily to the hybrid battery overheating and premature failure.

Remove the hybrid battery cooling fan by removing the three 10mm bolts holding the fan in place.  Unclip and unplug the four wire connector to finish removing the fan.  

After cleaning the fans, do not yet reinstall them into the vehicle.

27) Lay the car harness into the vehicle as shown.

If not already done, remove each of the hybrid battery cooling fans as shown in the photo at left.

28) Plug in the three hybrid battery cooling fan control sub-assembly boxes to their respective fans.  Do no reinstall the fans yet.

Tuck the hybrid battery cooling fan control sub-assembly under battery compartment.

Install the enclosure & right section of wire harness as shown using the supplied small zip tie.  Note that the red & black HV wires are secured by the same zip tie holding the fan plug in place.

Route the red & black HV wires into the battery compartment as shown.

Reinstall the right cooling fan.

It should look like this when done.

29) Carefully connect black HV negative wire to the right battery bank 8mm bolt as shown.

When tightening the battery bank terminal 8mm nut, DO NOT OVERTIGHTEN! These post can break if too much force is used. They should only be torqued to approx 4-5 ft lb.

30) Close 8mm battery bank terminal nut cover and secure black HV negative wire with provided small zip tie as shown.

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31) If you previously reinstalled the center battery cooling fan, remove it.  The fan needs to be shifted out of the way to gain access to the red HV positive wire connection point.

32) To connect the red HV positive wire, begin by removing the center battery bank rear end cover as shown.  There are two rows of clips.  One where the small flat head screw driver is located in the phot, and one a little lower.  

The battery end cover is removed by depressing the release tabs down and gently pulling on the cover.  

33) To gain access to the module end bolts, the center battery bank should be lifted slightly up.  This will allow the end cover to be easily shifted out of the way as well as gain access to the 8mm module end bolt.

Note in the photo how the battery bank is lifted up and resting on the rear mount bolts.

Also note we did not fully remove the end cover, but only shifted it to the side.  This reduces the chances of accidentally touching one of the battery module end bolts.

34) Connect the red HV positive wire as shown.  Torque to approx 4-5 ft lb.  Do not over tighten.

Secure the red HV positive wire with one of the provided small zip ties as shown.

35) Reinstall the center battery bank rear end cover.

Return the center battery bank to its proper position.

Install all battery cooling fans and secure with three 10mm bolts each.

It should look like this when done.

(Camry Hybrid shown
for reference)

36)IMPORTANT - Test the car harness installation before beginning re-assembly of the vehicle. We recommend that you connect the charger to the car harness before plugging it into the wall and unplug it from the wall before disconnecting it from the car harness.

To perform the initial function test: First, make sure all fingers and tools are clear of all wiring and hybrid battery components. Plug the charger into the car harness. With the hybrid battery main disconnect still removed, plug the charger into the wall. After a few seconds, it should read approx 360 volts on the meter and both the charger and three hybrid battery cooling fans should be running.

37) Turn the charger off.

Reconnect hybrid battery main disconnect.

Turn the charger back on.

(Camry Hybrid shown
for reference)

38) You should see the voltage has dropped drop as the charger voltage equalizes with the voltage level of the battery pack. The voltage level should be stable and not fluctuating. All fans should still be running.

If anything is wrong, stop and contact us. If the fans are ‘pulsing’ (powering on and off) every few seconds, stop and contact us.

This completes the test. Unplug the Charger from the AC power source and disconnect from the car harness.

39) Secure the rear portion of the car harness using the three remaining large zip ties as shown.

(Refer to disassembly
sequence for
respective image)

40) Reassemble the rear upholstery in the reverse order of removal:

Install the main battery cover

Install the battery disconnect cover

Install the three the three battery duct inlet brackets

Install the three hybrid battery exhaust duct covers

Fold the rear carpet down and install the three carpet clips and second row center seat belt latch anchor

Install the three hybrid battery cooling intake covers

Install the rear side panels

41) Route car harness through fuel filler slot on left rear side panel as shown.

(Refer to disassembly
sequence for
respective image)

42) Reassemble the rear upholstery in the reverse order of removal:

Install the four cargo net tie down anchors

Install second row seats

Install second row seat track trim

Install second row seat battery disconnect trim

Install second row step trim

(If equipped with third row seat:)

     - Install third row seat through the rear of vehicle

     - Install third seat upper crossbar

Install rear cargo trays

Install rear lift gate trunk sill trim

Install rear tail light covers

Install Rear Center Cargo Cover

43) This is what is should look like when you are finished.

(No image)

Click here for the Prolong Battery Charger User Guide.


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