2012 – 2017 Toyota Prius c (Aqua) Plug-and-Play Car Harness Installation Instructions

(Click on below image for larger photo)

Time Required: Approx 1-1.5 hours

Tools Required:
Trim panel removal tool
8mm, 10mm, 12mm, 14mm sockets
Zip tie cutters or scissors
#0 flat heat screwdriver
#2 phillips screwdriver
Recommended: Volt meter

1) Remove the rear seat floor mats.

Remove the two upholstery clips and remove the left outboard foot panel.

Remove the two upholstery clips and remove the right outboard foot panel.

2) Remove the three upholstery clips on the top of the center foot panel.

Tilt the top of the panel forward and lift to remove.


3) Remove the hybrid traction battery main disconnect by pulling down on the large orange disconnect lock ring, rotating it forward & up 90 degrees, and removing the disconnect.

4) Carefully unclip the lower seat side upholstery clip. One on each side of the seat bottom.

5) Firmly pull up on the front edge of the rear seat bottom cushion.

Raise the front of the seat bottom cushion up and slide forward to clear rear seat bracket.

Remove seat bottom cushion.

6) Remove two 14mm bolts from the bottom of the lower seat frame.

7) Remove two 14mm bolts from the top of the lower seat frame.

Carefully remove the lower seat frame.

8) Disconnect the 12V Aux battery negative.

Remove the hybrid battery exhaust duct retainer clip and remove the hybrid battery exhaust duct. Be careful to not scratch or damage the door sill trim.

9) Remove the right rear HV battery mount bolt.

10) Remove the right front HV battery mount nut.

(Not shown): Remove the left front HV battery mount nut.

11) Remove battery blower fan plug and retainer clip.

Remove three 10mm bolts and remove blower fan.

12) Remove the right rear HV battery mount bolt.

Using pin on top of battery disconnect switch handle loop, rotate safety clip lock at least 90 degrees counter clockwise to release safety lock pin.

Remove safety lock pin.

13) Remove four 10mm bolts and remove junction box top cover.

14) Unplug three HV battery wires and shift wires toward the back of the vehicle as shown.

15) Lift entire HV battery assembly and shift left side forward approx 1.5″-2″ as shown.

16) Remove two 10mm bolts and one 10mm nut.

Remove junction box side cover.

17) Using very small (#0) flat head screwdriver, carefully remove black battery module connection cover. It is not difficult, just take your time and do not rush this step.

18) Bend the supplied car harness Red HV+ charge wire as shown.

19) Remove top 8mm HV battery positive connection bolt. This is the HV+ (red wire) connection point.

20) Position the red HV+ wire as shown to prepare for installation.

21) Insert the red HV positive into the HV+ connection as shown.

Install the red HV positive wire using the previously removed 8mm bolt.

When tightening the battery module terminal, DO NOT OVERTIGHTEN! The bolt can break if too much force is used. They should only be torqued to approx 4-5 ft lb.

22) Do not close the black battery module connection cover yet, but this is what it will look like if the red HV+ wire is installed and routed properly.

23) Install black HV ground wire by routing up from below connection bolt as shown. Tighten 8mm bolt to approx 4-5 ft lb.

We used a piece of white paper to better illustrate the proper wire routing.

24) Close the black battery module connection cover and ensure it is firmly snapped into the proper position.

25) Routing the car harness wiring as shown, reinstall the junction box side cover, two 10mm bolts, and one 10mm nut.


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

Remove the hybrid battery cooling fan intake duct by removing the black retention clip. Reach into the fan and clean it in place or carefully remove the three 10mm bolts and remove the fan from the car to clean it.

27) Carefully return the HV battery assembly to its original location.

Connect Prolong Car Harness fan control box to hybrid battery fan and Reinstall HV blower fan and tighten blower fan mount bolts/nut.

Using large zip tie provided, secure hybrid battery cooling fan control box and fan wire harness to existing wire harness as shown.

28) Noting how car harness is routed, reinstall three HV battery wires to their original locations.

29) Reinstall the junction box cover and tighten the three 10mm nuts.

Reinstall the orange HV battery safety lock pin.

Using one of the small supplied zip ties, secure the car harness to the existing wire harness as shown.

30) Remove the rear cargo area carpet and left side support foam.

31) Route the wire harness into the rear cargo area as shown.

Using one of the provided zip ties, secure the wire harness to the seat bracket as shown.

32) Reinstall the left side support foam and rear cargo area carpet.

33)IMPORTANT – Test the charger before finishing 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 250 volts on the meter and both the charger and hybrid battery cooling fans should be running.

Note in the image at left the hybrid battery main disconnect is not present and the charger is displaying max voltage and no amperage.

34) Next, carefully connect hybrid battery main disconnect.


(2004-2009 diagram shown, but the locking action is the same.)

35) You should see the voltage drop as the charger voltage equalizes with the voltage level of the battery pack. This should happen quickly. The voltage level should be stable and not fluctuating. All fans should still be running.

Note in the image at left the hybrid battery main disconnect is present and the charger is displaying battery voltage and amperage.

If anything is wrong, stop and contact us. If the fan is ‘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 the Charger from the car harness. If the test was successful, you can leave the hybrid battery main disconnect in place.

36) Reassemble the rear seat area upholstery in the reverse order of removal:
Install the 14mm HV battery mount bolts & nuts.

Reconnect the Aux 12V battery ground wire.

Install the lower seat frame.

Install rear seat bottom.

Install the center & side seat trim panels.

Click here for the Prolong Battery Charger User Guide.