Features and Service Guide Part 1
Vehicle Handling SafetyGeneral Precautions
The Aura Green Line hybrid system uses a 36-volt battery pack located in the trunk area behind the rear seat, a belt-driven starter-generator and control electronics located on the driver's side of the engine bay at the core support.
To help avoid personal injury, always insure the ignition switch is in the OFF position and the ignition key has been removed prior to working on any 36V components. After the key has been removed disconnect the negative 12V battery cable and then open the generator battery disconnect control module cover. After waiting for at least 5 minuets, measure the voltage potential using a DMM between the following:
36V positive and negative battery cables
36V positive battery cable and vehicle ground
36V negative battery cable and vehicle ground
All measured voltage levels must be below 3 volts. After confirming that voltage levels are less then 3 volts, remove the 36V negative and then the positive battery cable.
All of the 36-volt circuits are identified with blue wiring conduit. The 36-volt system uses the vehicle chassis as a ground circuit in parallel with the conventional 12-volt system. Care should be taken when working near this 36-volt wiring and associated components. Refer to Hybrid Battery Service Disconnect/Connect in SI for 36-volt disconnect procedures.
First Responder Information
First responder information for all GM Hybrid products can be found on the Internet by following the Emergency Personnel Information link from http://gmstc.com. This central location will be maintained and provide the most current critical information for the first responder public. First responder information is available in English language only at this time.
Hybrid Service and Safety Training
U.S. Retailers: To enroll in and/or complete the following training, refer to http://www.gmtraining.com.
Canadian Retailers: Refer to latest training availability in the GM Canada Product Service Training Course Catalogue located on GM infoNET under Service & Body Training.
Pre-Delivery Inspection and Preparation
Performing a quality pre-delivery inspection (PDI) is one of the most important functions the Retailer can do for the customer. Most customers consider the condition of their new vehicle during delivery as a direct reflection of the Retailer and your service department. A quality PDI is essential to improving a customer's perception of your facility and increasing his/her satisfaction with their new vehicle.
U.S. Retailers: The Aura Green Line-specific PDI forms are available via DealerWorld. These forms contain the same generic PDI steps as before, but also include a section for Special Inspection Items. This section is updated monthly and contains special items to look for during the PDI process.
Canadian Retailers: Pre-Delivery Inspection forms are available for download from the GM infoNET.
Removal of Underhood Protective Covering on the Battery Cover
Please remove the protective covering from the Hybrid logo on the battery cover during the underhood inspection of the PDI process.
Customer Education and Unique Operating Characteristics
Customer Education
It is imperative that the customer be well informed about the unique features and operational characteristics of their Aura hybrid. For the sales team to be fully prepared, they should thoroughly review this New Model Features and Service Guide and use the Getting to Know Your Vehicle (GTK) guide (U.S. Only) as an outline when presenting a hybrid vehicle to a prospect.
Additionally, service and parts leadership, service writers and technicians should familiarize themselves with these materials to avoid attempting repair of normal operating characteristics.
Getting to Know Your Vehicle Guide (US Only)
A copy of the GTK can be found on the GM training web site (http://www.gmtraining.com) by following the links for Product Training> Product Information> GTK - Getting To Know Your Vehicle Brochures> Saturn. This guide is also included with the glove box materials within each vehicle.
Hybrid Overview - Hybrid Assist, Coast-down, Regenerative Braking and "Auto-Stop"
In general, the hybrid system uses battery power to assist the gasoline engine in accelerating and driving the vehicle. This is referred to as the hybrid assist mode of operation. The majority of the energy depleted from the battery is replenished during coasting and braking, using the moving vehicle to charge the battery. This mode is called regenerative braking. Additional charging can occur while driving, using power from the gasoline engine.
This cycle of the battery power assisting in the acceleration of the vehicle and being recharged during deceleration and braking results in a significant improvement in fuel economy.
In the hybrid assist mode of operation, the 2.4L LAT powertrain can provide a significant boost to performance. This additional performance will not typically generate any form of owner concern or negative comment.
However, during the coast-down and regenerative braking, the generator creates drag on the vehicle and feels more like a manual transmission (with engine braking) than a typical automatic transmission vehicle. This feeling of drag may result in owner comments or concerns developing. The sales team should feature this characteristic to prospects and owners upon delivery - stressing that this feeling is normal and desirable as the hybrid system recaptures energy from the moving vehicle. Additionally, during many of these coasting and regenerative braking events the engine is not being fueled at all, providing further fuel economy. This period of operation without fuel is called "deceleration fuel cut off."
As the vehicle slows and approaches a stop, fuel is returned to the engine and the regeneration is reduced. These actions reduce the drag on the vehicle, which then coasts more freely. This elimination of drag may be commented upon until the owner is accustomed to this normal operation.
Additional fuel economy is achieved through the "Auto-Stop" when the vehicle comes to a complete stop. In the "Auto-Stop" mode the engine completely stops and, therefore, uses no fuel. As the operator releases the brake, the hybrid system will restart the engine and the cycle repeats.
Conditions Required for "Auto-Stop" Reasons for No "Auto-Stop" or Early "Auto-Stop"
There are a number of system requirements that must be satisfied for the engine to be commanded to "Auto-Stop." These requirements include:
The engine must be running, the shifter must be in Drive and at a complete stop with the hood closed and the brakes applied.
The vehicle must have been driven above a specific speed (5 mph [8 km/h]). Outside air, engine, transmission and hybrid battery temperatures are in acceptable ranges.
No command for A/C compressor operation (HVAC system not in Defrost or Normal A/C) and evaporator temperature low enough if in hybrid A/C mode.
Sufficient state of charge of both hybrid (36-volt) and 12-volt batteries and electrical load not too high.
Sufficient vacuum level at brake booster, vehicle not on an extreme grade and no wheel slip.
No malfunction codes (DTCs) set and no evaporative emissions (EVAP) tests running.
After the vehicle goes into an "Auto-Stop," it will only remain in "Auto-Stop" for a maximum of 2 minutes. Additionally, if any of the required conditions change, the engine may re-start at any point in this 2 minute cycle, like:
The driver relaxes the brake or opens the throttle.
The HVAC evaporator temperature increases too much or the HVAC mode or air delivery is changed.
The brake booster pressure rises too much.
The electrical load is significantly increased.
Many of the conditions that allow, or shorten, an "Auto-Stop" are not visible or controllable by the operator. In general, an occasionally skipped "Auto-Stop" should be considered normal. If a system malfunction is the cause for loss of "Auto-Stop," a malfunction code (DTC) will be set.
Refer to the How to Maximize Fuel Economy section below for tips on increasing the occurrence and length of the "Auto-Stop" mode.
How to Maximize Fuel Economy
Although the hybrid Aura is rated at 28 mpg/city and 35 mph/highway U.S. (8.5 L/100 km city and ? 6.2 L/100 km highway in Canada), fuel economy can vary greatly depending upon how the vehicle is driven. The measurement of fuel economy during vehicle break-in will typically generate lower numbers. Measured fuel economy will tend to stabilize after the first 1000 miles (1600 km). After this initial period, there are several techniques that can help maximize fuel economy.
Use of "ECO" light
The green "ECO," or economy, telltale was added to the cluster to inform the operator that they are achieving, or exceeding, the rated fuel economy for the given driving speed. Using this light as a guide will improve the fuel economy experience.
This light can be disabled using the DIC buttons on the steering wheel. With the engine off and the key turned to accessory, set the DIC to the outside air temperature and odometer mode. Press and hold the reset button for several seconds. The light will come on solid and then flash several times and turn off to indicate that it is disabled. Repeat the procedure to enable the light.
Vehicle Acceleration
A significant amount of fuel is used in vehicle acceleration. To improve economy, accelerate smoothly and gradually with the lowest reasonable throttle level. As you approach your desired speed, reduce throttle until the green "ECO" light illuminates. Attempt to keep the "ECO" light illuminated whenever driving at a constant speed. Allowing a drop in speed when climbing a grade will save fuel over increasing the throttle to maintain a given speed.
Coasting and Braking
During many coast conditions, the hybrid vehicle achieves its highest fuel economy as engine fuel flow can be shut off and regenerative braking charges the batteries. In contrast, braking converts the energy of the moving vehicle into heat - which cannot be recovered. To maximize economy, rather than "driving" with the throttle applied up to traffic, a light or stop sign, the operator should begin coasting sooner allowing regenerative braking to slow the vehicle more gradually. In short, begin coasting sooner, and brake less.