schmidtj — Thanks for posting this important TSB. Please continue to do so for all relevant TSBs for the TCH. Thanks!

Looking at the simplified circuit diagrams (the only ones available) in the Repair Manual, I see that the Hybrid Battery Precharge Contactor Circuit uses a solid-state (MOSFET) switch to pre-charge the large high-voltage capacitors inside the MGs' dc boost converter and ac inverter electronics in the engine compartment (above the MGs and planetary gear case). This is done to prevent arcing and consequent deterioration of the hybrid battery relay contacts due to the high peak charging current that would otherwise flow from the battery into the capacitors at switch-on. The MOSFET allows these capacitors to charge slowly through a resistor, thus reducing the peak charging current, before the main relay contacts close. [This happens during the 1-second "pause" just before the ICE starts ~10 seconds after switch-on.] If the pre-charge circuit fails in the "stuck closed" condition, as indicated in the TSB, this charging resistor would always be switched into the circuit, but since the relay in the other wire would still "open" when the vehicle is switched "off," no electrical damage would occur, and I think it would be quite safe to continue to drive the car until you can get the dc/dc Converter Assembly replaced, as per the TSB. This unit is in the trunk, behind (i.e., towards the front of the car relative to) the NiMH battery.

nash and skywagon — In the failed condition, the orange high-voltage wires from the battery to the engine compartment would not be completely isolated from high voltage when the car is "off," and this could be a potential hazard for service personnel or for rescue workers at an accident. So, it is important to have the unit replaced. I would think that it would be best to have it done in the near future, at one's convenience, rather than wait for a possible failure to occur at a later, less convenient, time.

Stan