“The fuel cell stack coolant leak can occur as a result of two potential causes: (1) insufficient verification during a process change to reduce the amount of adhesive sealant resulted in unfilled areas, shortened adhesive length, and reduced sealing performance of the FC stack assembly end joint, and (2) the supplier (Fuel Cell System Manufacturing Brownstown Township, MI) failed to establish a deburring process for the O-ring groove of the wobble joint, resulting in burrs which reduced sealing performance. Over time, these conditions can allow fuel cell stack coolant to enter the FC stack case and create an electrical short between the fuel cell stack bipolar plate and the support-bar housing, leading to the ground-fault warning,” Honda said in the required safety defect recall filing with the National Highway Traffic Safety Administration.

Driver Warnings

Multiple warnings will be displayed in the instrument cluster through the progressive stages of fuel cell stack coolant leakage before the loss of drive power.

• “Power System” warning will display when a high voltage ground fault is detected (DTC: P0AA6) and stored
• “FC insulating fluid low. See your dealer.” warning will display when the fuel cell stack coolant (insulating fluid) level has decreased in the reserve tank.
• “Power may be reduced. See your dealer” warning will display when air is mixed into the fuel cell stack coolant, and the FC power output is reduced to 20kW.
• “Do not drive” or “Stop driving when safe” will display when the fuel cell stack coolant temperature rises and the FC power generation has stopped.