Perceived Poor Fuel Economy or Lack of Auto Stop Informational- keywords cold delay hot mode two

This PI was superceded to add models and update year. Please discard PIP4332.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Customer may comment that the Auto Stop function does not operate at all in hot or cold temperatures or takes a long time to activate in cold ambient temperatures. Customers may also comment that fuel economy is less that expected. This concern may be considered a normal Condition with certain conditions and driving maneuvers.

Inform customer that environmental conditions and driving habits have a direct correlation with fuel economy. The Auto Stop mode may not be enabled if certain hybrid and vehicle components are too hot or too cold. In winter; the hybrid battery module temperature, engine coolant temperature, transmission fluid temperature, and cabin temperature must be warmed up before Auto Stop is allowed. The hybrid controllers also monitor ambient temperatures and interior temperature along with the above mentioned criteria to determine desired Auto Stop conditions.

In cold temperatures, the Auto Stop criteria are highly dependant on the outside air ambient temperature. Depending upon the over night soak time, specific drive cycles, and the factors listed above, it may take an hour before the fist Auto Stop occurs. In the summer, the hybrid batteries, the hybrid cooling system and the engine must all be kept cool for Auto Stop mode. Running the interior air conditioning and keeping the hybrid battery vents unrestricted will help keep the hybrid batteries cool.

Heavy acceleration requires more engine operation and thus more fuel consumption. Heavy braking does not allow regenerative braking to occur. Fuel economy will be the same as base truck under heavy throttle and brake apply. Adjusting both braking and acceleration driving habits will result in the highest system efficiency. Refer customer to monitor Active Fuel Management (AFM) information on the Hybrid Navigation/Radio Display Screen or the efficiency gage to learn Driving Habits/Conditions that improve fuel economy. This includes trying to keep the efficiency gage in the "green zone" as much as possible and try to drive in 4-cylinder mode as long as possible.

The transmission gear shift selector should be placed in Drive and not in manual for best fuel economy. Auto Stop is inhibited in the manual transmission shift ranges.

Additional tips to improve fuel economy include keeping tires properly inflated, accelerating to allow for as much Mode 1 electric propulsion as possible, limiting the use of remote start, reasonable highway speeds, minimize carrying unnecessary cargo or mass, and keep the Transfer Case in 2WD instead of Auto for best fuel economy.

If there are no DTCs found in the vehicle modules that would prohibit Auto-Stop and the hood switch reads correctly, this condition will be considered an operating characteristic The technician can monitor the HPCM (Hybrid Powertrain Control Module) and "Auto-Stop Inhibit Reasons" data list to identify the normal inhibit reason.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.