Lately, we've been seeing several 2014 Malibus with the autostart system. These are not hybrids. For people who have not seen them yet, they use the 2.5 engine and a specialized starter to operate an autostart operation similar to a hybrid.

Under the hood, there is a large 850 CCA AGM battery and a smaller (lawnmower size) 155 CCA AGM battery mounted in the trunk. The system uses a battery sensor module wired to the BCM through a LIN network, a dual battery isolation module and an analog battery current sensor. There is quite a bit more involved but I'm trying to keep it simple.

During an autostop, the HVAC system is operational although the compressor is not turning and feels normal during a normal stop light stop. The transmission pressure is maintained with an auxiliary pump and the heater will continue to function with an electric coolant heater pump.

When the brake pedal is released, and the vehicle autostarts, the main battery is isolated to the starter only by the dual battery isolation module while the smaller trunk mounted battery is switched into the circuits to power the accessories. I just had one in the shop with a P305F set current and autostop disabled. The code description is for "Dual Battery Isolation Performance". The code sets when the voltage at the run/crank input of the ECM drops below 9 volt for more than 1 second.

I tested the main battery with the GR-8 and it passed. The rear battery cannot yet be tested the same way. (software updates coming) Measuring the rear battery voltage with vehicle running was 13.8 volts. After 10 minutes with key off, open circuit voltage was 12.28 volts. I replaced the rear battery with a new unit that had an open circuit voltage of 12.59 volts and solved the problem. The vehicle requires a auxiliary battery that is strong enough to operate the accessories before it will allow autostop/start.

James from Florida