2016-2020 Toyota Prius (NiMh only) Plug-and-Play Car Harness Installation Instructions

(Click on below image for larger photo)

Time Required: Approx 1.5-2 hours

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

NOTE: While not required, having an 8mm offset wrench like shown in the photo will make installing the Prolong Car Harness will be much easier.
We purchased ours on Amazon for just under $10

1) On bottom foot area of rear seat, remove HV battery fan inlet cover

2) Disconnect and remove the orange HV battery disconnect switch. Refer to this video for proper removal and installation of the HV battery disconnect switch: https://youtu.be/dHwr4Iq9HZI

3) Remove the rear door rubber seals and lower sill step trim

4) Remove rear seat bottom. It is not necessary to remove the rear seat backs

5) Remove the battery compartment side cover trim

6) Remove the rear seat support bracket that crosses over the top of the hybrid battery

OPTIONAL BUT RECOMMENDED:

We highly recommend taking a few extra minutes to clean the hybrid battery cooling fan intake screen. The fan intake often becomes clogged with debris. This contributes heavily to the hybrid battery overheating and premature failure.

7) Remove the hybrid battery connections cover located on the passenger side top of the battery

8) Remove the 10mm bolts on the front side of the hybrid battery pack main cover

9) Remove the 10mm bolts on the top of the hybrid battery pack main cover. Lift the main cover up and out of the way

10) Carefully remove the right-rear black module end cover from the hybrid battery. It has clips at the very top and about half way down the black trim cover. A very small flat head screw driver makes this easier.

11) The Prolong Car Harness black battery negative wire will connect to the rear passenger corner of the battery pack. It connects to the back side of the module, like shown in the photo. Carefully install the black wire using an 8mm offset wrench. If desired, cover the battery enclosure cover metal with a manilla folder to provide electrical insulation.

12) Carefully remove the left-rear black module end cover from the hybrid battery. It has clips at the very top and about half way down the black trim cover. A very small flat head screw driver makes this easier.

13) The Prolong Car Harness black battery negative wire will connect to the rear driver corner of the battery pack. It connects to the back side of the module, like shown in the photo. Carefully install the black wire using an 8mm offset wrench. If desired, cover the battery enclosure cover metal with a manilla folder to provide electrical insulation.

14) Route the high voltage wires out of the battery box as shown in the photo at left

15) Connect the Prolong Car Harness fan control module to the hybrid battery cooling fan by unplugging the fan connector and connecting the harness in line with the fan. The Prolong Car Harness fan control box can be stored in this recessed area behind the cooling fan.

16) Open the truck, remove the truck carpet, and the spare tire cover foam.

17) On the right side trunk floor foam, remove the black plastic pocket clip as shown in this photo.

18) Slightly shift the front of the right side trunk floor foam toward the center of the vehicle as shown in this photo

19) Route the Prolong Car Harness into the truck area as shown in this photo

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. (2004-2009 Prius image shown at left for reference.)

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

20) Next, power the system off, then carefully connect hybrid battery main disconnect. Refer to this video for proper removal and installation of the HV battery disconnect switch: https://youtu.be/dHwr4Iq9HZI

21) Power the charger back on. You should see 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. (2004-2009 Prius image shown at left for reference.)

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, remove the orange battery disconnect switch, and disconnect the Charger from the car harness

22) When not in use, the harness can be stored under the trunk carpet in the recessed area shown in this photo

Reassemble the vehicle in the reverse order of disassembly.

Click here for the Prolong Battery Charger User Guide.

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