Hybrid Systems - Service Guide/Operating Characteristics: Overview
INFORMATIONBulletin No.: 07-00-89-059G
Date: August 17, 2011
Subject: Service Guide, Unique Characteristics and Normal Operating Conditions for Two-Mode Hybrid Models
Models:
2009-2012 Cadillac Escalade Hybrid
2008-2012 Chevrolet Tahoe Hybrid
2009-2012 Chevrolet Silverado Hybrid
2008-2012 GMC Yukon Hybrid
2009-2012 GMC Sierra Hybrid
All Equipped With 2-Mode Hybrid Option (RPO HP2)
Supercedes:
This bulletin is being revised to add the 2012 model year. Please discard Corporate Bulletin Number 07-00-89-059F (Section 00 - General Information).
Notice
- Diagnosis and repair of Two-mode propulsion systems, two-mode high voltage systems, M99 Transmission, LFA engine, regenerative brake apply systems and HVAC systems MUST be performed by dealers who both sell and service Two-mode vehicles. Dealers must have the essential tools and personal protective equipment and technicians performing hybrid repairs must have completed all available training prior to proceeding with repairs on the unique hybrid components.
- If your dealership is not a Two-mode hybrid sales and servicing dealership with a trained technician, then the vehicle must be transferred to a dealership that meets these requirements.
SAFETY PRECAUTIONS
Danger
To reduce the risk of severe shock and burns, treat all high voltage cables and connectors as though they are energized until it can be verified that they are not.
Danger
Any service to the hybrid system or any related component requires the removal of the key from the ignition. If the key is left in the Run position, failure to remove the key from the ignition could cause the engine to auto-start, and in the Off position, the 300V system could remain active. The first step of disabling the high-voltage system is to remove the key from the ignition, which is designed to open the contactors in the battery pack, beginning the process of powering down the high-voltage system.
Danger
Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.The High Voltage Disabling procedure will perform the following tasks:
- Identify how to disable high voltage.
- Identify how to test for the presence of high voltage.
- Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
Failure to follow the procedures exactly as written may result in serious injury or death.
Warning
The hood ajar switch communicates whether the hood is open or closed. If the ignition is in the "on" position and the vehicle is in auto-stop, the engine will re-start automatically when the hood is opened.
Unique Characteristics and Normal Operating Conditions
Drivers of the Two-mode Hybrids will experience some operating characteristics that are unique to these vehicles. Due to the quiet nature of the Hybrid Drive system, certain sounds that may have been masked by the engine's natural harmonics will be apparent. Among them is the electric engine cooling fan, the air conditioning compressor and the HVAC blower. In addition to those sounds, the drive motor battery assembly cooling fan, which sounds like the HVAC blower on low speed, may be heard from under the second row seat.
Key Crank Engine Start Characteristics
This is a normal characteristic of the vehicle. If the engine will not crank, ensure that the 12v battery is sufficiently charged to allow for all of the hybrid control modules to "wake up" and initialize. The Two-Mode Hybrid does not use a conventional 12v starter- it uses one of the electric motors in the transmission to crank the engine that spins the engine faster than a 12v starter, resulting in different than typical starting noise.
Stall During Shift Out of Park Immediately following Engine Crank
This is a normal operating characteristic. Some drivers are able to interrupt the engine start sequence by immediately shifting the transmission out of Park after turning the ignition to Crank. Because the electric motor spins the engine so fast, the engine may appear to be running immediately after Crank but the ECM has not yet started spark and fuel. The ECM will turn off fuel and spark to the engine if it is not running and the transmission has been shifted out of Park or Neutral. Inform the customer to wait 1-2 seconds before shifting out of Park or Neutral to ensure that the engine is running and has completed the start sequence.
Engine Restarts in Reverse/Manual Mode from Auto Stop
This is a normal operating characteristic - engine will restart any time the gear selector is in reverse or Manual Mode. Reverse remains in electric mode, however, the engine restarts to provide counter-torque for the internal transmission gears. 2010-2012 models are designed to operate in reverse without the engine running, depending upon HV battery state of charge.
Slight Bump in Driveline during Acceleration
This is due to transition from V4 to V8 and vice versa. In Mode 2, the engine is able to operate longer in 4-cylinder mode under light throttle for improved highway fuel economy. As more power is needed, the system will transition into V8 Mode. This is a normal operating characteristic of hybrid powertrain to maximize fuel economy.
Low Level Noise during Auto Stop
This is a normal characteristic operation of electric coolant pump or hybrid battery fan. During Auto Stop the engine is not running and the interior cabin is quiet. These pumps run to keep the electronics from overheating, even in cold ambient temperatures. This noise may be more evident during high ambient interior temperatures. Advise the customer to keep the battery vents clear and not to carry cargo in the second row footwell area. The electric coolant pump runs in Autostop to circulate coolant to the HVAC system to maintain cabin temperature. That pump (under the right conditions) will run and may be barely audible.
Cruise Control Resume Operation
The Hybrid System is optimized for highest possible fuel economy. The Two-Mode hybrid vehicle resumes previously set vehicle speed at a rate which provides maximum fuel economy.
Brake Pedal Feel and Brake Pedal Vibration
- The Two-mode Hybrid System has a unique brake pedal feel. This is because the hydraulic system is not the lone provider of vehicle deceleration. The hybrid system blends in regenerative and hydraulic braking forces depending upon vehicle conditions. Over several braking events, the customer may perceive that they are applying a consistent brake force and yet the vehicle may decelerate at slightly different rates. This is a normal operating characteristic to maximize fuel economy.
- The Two-Mode hybrid vehicle utilizes a braking system that employs a high-speed electric motor/pump. Pump operation can sometimes be heard and felt in the brake pedal as the system sometimes builds pressure. This is most noticeable to customers who start the vehicle with their foot on the brake pedal.
12 Volt Operation
- In order to maintain the peak capacity in the 12-volt system, it is recommended that customers allow the vehicle to remain in "run" when parked and attended ONLY AFTER cranking and starting the engine. When the ignition switch has been turned to crank and is set to "run" the engine will run until the desired state of charge in the 300V battery has been reached. At that point, the vehicle will enter auto-stop mode, and the Accessory Power Module (APM) will continue to power the 12-volt system. Failing to allow the APM to power the 12-volt system could cause discharge of the 12-volt battery. Examples of activities that may cause stress on the 12 volt battery include:
- Tailgate celebrations
- Usage of the rear seat entertainment system with the vehicle off
- Listening to the radio for extended periods of time with the vehicle off
- In the above situations, the recommended operating mode is to start the engine. Normally the vehicle will enter auto-stop mode and as the 12-volt battery needs charging, the system will automatically start the engine to keep the system fully charged.
- In addition to allowing the APM to power the vehicle's 12-volt system, special care should be taken when storing this vehicle. If the vehicle is to be stored for more than 20 days, the 12-volt battery should be disconnected. If the vehicle is to be stored for more than 60 days, the 12-volt battery should be charged to capacity no less than once every 20 days.
- You must wait at least 5 minutes after turning the ignition OFF before disconnecting the 12V battery for any reason. This allows the hybrid control modules to process and store internal data.
Whine Sound during Electric Hybrid Operation
Due to the hybrid nature of the vehicle, the electric motor may be heard as the vehicle moves. This is a normal operating characteristic.
No Brake Assist (Hard Pedal) After Disconnecting Battery
Customers or technicians that are disconnecting the battery must wait for a period of at least 5 minutes with the ignition in the "OFF" position without pausing at ACCESSORY, and without applying the brake pedal prior to disconnecting the 12 Volt battery. These steps are necessary to allow the brake system pressure relief procedure to occur.
Caution
Failure to follow these steps may result in warning lamps and/or DTCs being set pertaining to interruption of the pressure relief procedure. Other vehicle systems may also be affected by not allowing a 5 minute duration for power-down.
Other New Hybrid Features
Drive Motor Battery Assembly
The drive motor battery assembly is serviced as a unit at this point.
The drive motor battery assembly is also known as a battery pack. The drive motor battery assembly is housed under the second row bench seat, and is enclosed in a steel box. Inside the drive motor battery assembly is a set of NiMH battery cells, the controller, a cooling fan, and a set of contactors that will engage only when the controller tells them to. When the controller indicates it is okay to close the contactors within the drive motor battery assembly, the series-wired NiMH battery cells and their 300V of potential are connected to the rest of the Hybrid system.
One input to the drive motor battery assembly controller is the High Voltage Interlock Circuit system, or HVIC system. The HVIC system is comprised of a series of switches that if opened, may command the controller to open the contactors of the drive motor battery assembly. This will prevent the Hybrid system from operating. These switches are located in the following locations:
- On the PIM cover under the hood.
- On the main power disconnect at the drive motor battery assembly.
- On the terminal cover for the high voltage connections on the drive motor battery assembly.
- On the transmission where the high voltage cables connect.
PIM/APM (Power Inverter Module/Accessory Power Module)
The Power Inverter Module (PIM) and Accessory Power Module (APM) are located under the hood on the right side of the engine compartment and are referred to as the Drive Motor Control Module Assembly. The PIM is a high voltage high speed switching device that uses 300V DC and converts it to 300V 3 Phase AC to power the electric motors in the transmissions during Hybrid operation. The PIM is also able to take 300V 3 Phase AC from the electric motors, either during battery charging, or during a regenerative braking event and convert it into 300V DC to charge the drive motor battery assembly. The PIM can get very hot during operation, so a discreet cooling system has been integrated into the design. Included in the power electronics cooling are:
- Two electric circulation pumps.
- An isolated reservoir.
- A radiator specific to the power electronics cooling system.
- Hoses for the system.
Caution
It is important to note that while the power electronics cooling system uses DEXCOOL, IT MUST be mixed with deionized water to prevent corrosion within the PIM/APM assembly. Pre-Mixed DEXCOOL contains the correct ratio of de-ionized water and should be used to service the power electronics cooling system. This coolant does not mix in any way with engine coolant.
The APM is a module that converts 300 Volts to provide a 12V power feed to keep the standard service battery charged. It also provides a 42V feed for the Electronic Power Steering.
Tire Inflator Module
The Two-mode Hybrids feature a tire inflation kit instead of a spare tire. In the event of a flat tire, the tire sealer should be used in combination with the air compressor to inflate the tire. The tire inflation kit is located in the left rear storage compartment, where the jack is normally located. It is important to note that there is no spare tire, and the tires are not run-flat tires. Any tire or wheel damage that is not repairable with the tire sealer and air compressor requires that the vehicle be flat-bed carried to the nearest tire repair facility.
Aerodynamic changes
The Two-mode Hybrids offer improved aerodynamics over the standard vehicle. The improvements are achieved by a multitude of changes. The following are some of the aerodynamic changes:
- Removal of both fog light openings and tow hook openings on the front fascia.
- Lowering the fascia by an additional 76 mm (3 in).
- Lowering the suspension by 10 mm (0.39 in).
- Removal of the roof rail luggage rack.
- Changing the overhang of the rear deck lid and rear fascia.
These changes have enabled about a 2% decrease in wind resistance, in addition to weight savings, which translates into better fuel economy.
Brakes
The service brakes on the Two-mode Hybrids are unique. The base brakes are blended with electric motor braking and a brake pedal emulator provides feedback to the driver. There is no vacuum brake booster for the master cylinder. Instead, there is a hydraulic accumulator and a high-speed, fast acting pump that provides brake pressure boost to the hydraulic system. ABS and Stabilitrak are a standard feature of the Two-mode Hybrids.
EPS (Electronic Power Steering)
Power Steering on the Two-mode Hybrid is achieved without the use of a hydraulic rack and pinion and belt driven pump. For these models, power steering is achieved with a rack-mounted 42V electric assist motor. Using an electric motor instead of a belt driven pump and hydraulic rack enables power steering operation to continue while the engine is in auto-stop.
Air Conditioning
The Two-mode Hybrid SUV's have no belt drive air conditioning (A/C) compressor. Instead, there is a 300V A/C compressor that bolts into the same location as a standard belt-driven A/C compressor. The A/C compressor includes a high-voltage A/C pump and an inverter module that converts 300V DC from the APM into 300V 3-phase alternating current. The A/C compressor is serviced as a unit, and uses POE (Polyol Ester) refrigerant oil instead of PAG (Polyalkylene Glycol) because it is less hygroscopic. The purpose of using an electric air conditioning compressor instead of a belt driven compressor is to provide air conditioning performance while the engine is in auto-stop. The A/C compressor features a high RPM scroll compressor that is pulse width modulated. During conditions with high ambient temperatures and high humidity, the driver may notice a unique high-pitched sound from the compressor. This is considered a normal characteristic, and it will be heard most noticeably in auto stop mode with the window lowered.
Weight Savings
With the deletion of the spare tire (and roof rack on the Tahoe and Yukon), weight savings was achieved. Above and beyond that, engineers worked hard to find solutions that would offset the additional weight of the drive motor battery assembly and transmission assembly. They achieved that offset by utilizing premium materials that, while offering less mass, are just as strong as the materials traditionally used. The front lower control arms and the rear propeller shaft are made of aluminum. The second row seat was redesigned to incorporate the drive motor battery assembly, as well as to reduce weight.
Other Standard Features
Navigation radios are standard in the Hybrid Tahoe, Yukon and Escalade. In addition to the functionality of the navigation system, there is an additional feature that is unique to the Hybrids. When utilizing the navigation system users will notice that under the MENU tab, there is a graphic display of the hybrid system and its operational state. When the vehicle is in auto-stop, the display indicates that the engine is not running and the vehicle is not moving. When the vehicle is in mode one, the display indicates that power stored in the drive motor battery assembly is being used to propel the vehicle forward. When the vehicle transitions to mode 2, the display indicates that the engine is propelling the vehicle, and the electric motors are helping (Hybrid mode). When the vehicle is braking, it indicates that there is electricity being generated and stored in the drive motor battery assembly for future use (Regen mode). A 110V, 150W power outlet is located behind the third row of seats along the window sill near the tire inflation kit. Typically, 150 watts is enough power to charge two cell phones, charge one laptop, or maintain two laptop charges, but is not intended for heavy-duty usage.
SPECIAL TOOLS
Essential tool shipments for select dealers (Visual Display Eligible) have been completed. Future Hybrid Essential Tool shipments will be based on training completion. Hybrid essential tools will be shipped automatically to dealers meeting Hybrid training requirements. If immediate assistance is needed for Hybrid tools, contact SPX at 1-800-GMTOOLS (prompt #3 then prompt #1) and request GM Two-Mode Essential Tools. Provide the customer service agent with dealership information as requested. Tools will be invoiced through the dealer parts account.
Safety Gloves & Sleeves
Three sets of rubber electrical insulation gloves (S, M, L) and protective leather sleeves are included in EL-48900 Safety Kit.
Gloves and sleeves meet the necessary safety specifications for working on hybrid vehicles. Reference OSHA standard (1910.37) for testing and *re-certification of gloves and sleeves.
U.S. standards
- Gloves and sleeves are marked with the date of manufacture and electrical test and are acceptable for use 12 months from date of manufacture and electrical test.
- If put in service before 12 months from test date, retest must occur 6 months from in-service date.
- If the in-service date is not known, the gloves/sleeves should be retested 6 months from the test date stamped on the glove/sleeve.
Canadian standards
The gloves/sleeves must be retested / re-certified six months from the test date stamped on the glove/sleeve.
*For U.S. reference - Visit the North American Independent Laboratory website at www.nail4pet.org for an accredited laboratory for re-certification.
*For Canadian reference - Visit the Lineman's Testing Laboratories of Canada Ltd. website at http://www.ltl.ca/ for an accredited laboratory for re-certification.
AVAILABLE TRAINING
For future classes, visit www.gmtraining.com (U.S.) or www.gmprocanada (Canada).
Warranty Information
The Two-mode Hybrid Tahoe, Yukon and Escalade vehicles will have multiple warranties on them. The hybrid powertrain will carry an 8 year, 100,000 mile (160,000 kilometer) warranty. The non-hybrid specific powertrain will carry the same 5 year 100,000 mile (160,000 kilometer) coverage as the base truck. The emissions warranty and bumper-to-bumper (Base Warranty in Canada) has not changed.
Disclaimer