Toyota Highlander Issues
Some 2014-2018 Toyota Highlander and Highlander Hybrid vehicles may exhibit one or more of the following conditions:
Various drivability concerns
Low or no fuel pressure
DTCs including but are not limited to P1603, P1604, P1605, P0171, P0300, P0302, P0304 and U0100
Some Hybrid Highlanders may also exhibit DTC P134A
These conditions may be caused by corrosion/water in the A43 ECM connector (Highlander) or the A9 inverter water pump connector (Highlander HV). The corrosion in the A43 and A9 connectors is due to poorly sealed or damaged aftermarket windshield deicer harnesses. Also, check the condition of A33 front wiper deicer windshield glass connector on either model.
Check the condition of the afore-mentioned connectors for signs of corrosion/damage. According to Toyota, if the damage is found in a non-Hybrid vehicle, replace the ECM, the engine room main harness and the windshield. On a Hybrid model, replace the inverter water pump, engine room main harness and windshield. Toyota notes that it strongly recommends replacing the windshield with a Toyota genuine part, which has special seals to prevent water/moisture from entering the engine room main harness, as some aftermarket windshields do not have these seals.
A9 connector on the Highlander Hybrid.
A33 front wiper deicer connector.