GMC Yukon and Chevy Taho Two-Mode

8/9/2019 GMC Yukon and Chevy Taho Two-Mode

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2008 GMC Yukon & ChevroletTahoe Two-mode Vehicles

EmergencyResponseGuide


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he intent of this guide is to provideinformation to help you respond toemergency situations involving the2008 GMC Yukon & ChevroletTahoe Two-mode vehicles in as safe

a manner as possible.

While the majority of the componentsthat make up our Hybrids arecommon to traditional GM vehicles,there are some differences that mayaffect how a rescue procedure is

performed.This guide contains a generaldescription of how the 2008 GMCYukon & Chevrolet Tahoe Two-modevehicle systems operate, gives thelocation of their Hybrid badging, and

offers illustrations of their uniquecomponents. The guide alsodescribes methods of disabling thesystem and presents cut zoneinformation.

T


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Vehicle Identification

Special badging is used to identify the 2008 GMCYukon & Chevrolet Tahoe Two-mode Hybrid

vehicles. One of these emblems is located on thelower right corner of the vehicles liftgate.

Also the eighth digit of the Vehicle IdentificationNumber (VIN) can also be used to identify a Two-

mode Hybrid vehicle. If the eighth digit is a five(5), this signifies the vehicle is a Hybrid.


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Vehicle Identification (cont.)

A Hybrid badge is also located on the right and left C-pillarsof the 2008 GMC Yukon & Chevrolet Tahoe Two-modeHybrid vehicles.


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A tachometer with Auto Stop indicator and an Economygauge are unique to the 2008 GMC Yukon & ChevroletTahoe Two-mode Hybrid vehicles.

Tachometer withAuto StopIndicator Economy Gauge


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When the hood is opened, indications that aTwo-mode Hybrid system is present include aHybrid badge and a HIGH VOLTAGEWARNING label on the power electronics cover.


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Under the second row, rear seat sub-floor is a DANGER HIGH VOLTAGElabel attached to the Hybrid batterycase, indicating high voltage.


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System Operation

The 2008 GMC Yukon & ChevroletTahoe Two-mode vehicles are gasoline-electric Hybrid SUVs that use up to 25

percent less fuel overall and 40% lessfuel in the city, than the non-Hybrid 2008GMC Yukon & Chevrolet Tahoevehicles.

Introduced in the Fall of 2007, the Hybridmodel uses a 300 volt electrical systemcoupled with a Hybrid transmission andsophisticated technology to achieve itsfuel savings.

The vehicle is equipped with a 6.0 liter,Variable Valve Timing (VVT) engine, as

well as 300 volt, 42 volt and traditional12 volt electrical systems.


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System Operation (cont.)

During braking and deceleration, energy is recoveredand stored in the Two-mode Hybrid battery, this isreferred to as Regenerative Braking. Another Hybridfeature is the Auto Stop Mode. The system is designed

to shut off the engine at speeds below 25 miles per hourat low throttle angle, or low torque request, whenconditions permit.

During vehicle launch the electric motors within thetransmission can propel the vehicle to around 25 milesper hour before the engine is restarted. Other conditions

that will cause the engine to restart from Auto StopMode include:

Additional torque is requested for fasteracceleration

Hood is opened

Hybrid battery charge is low and requiresrecharging

Gear selector is moved to Manual

Climate control system requires engine operationto generate heat


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DC Voltage Classifications

The 2008 GMC Yukon & Chevrolet Tahoe Two-modeHybrid vehicles use higher voltage than other Hybridsyou may have encountered - they MUST beapproached with caution.


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Color coding is used to identify the different levels blue for intermediate voltage cables and orange for highvoltage cables.

The 2008 GMC Yukon & Chevrolet Tahoe Two-mode Hybrid vehicles fall within both the Intermediate and the high

voltage range.

Two-mode Hybrids utilize 300v (both AC and DC) for Hybrid System operation. A 120v AC Accessory PowerOutlet (APO) is provided at the left, rear corner of the cargo area. Also, a 42v system supplies the Electric PowerSteering (EPS) System.

DC/AC Voltage Classifications

GM has categorized voltage levels aseither low, intermediate, or high voltage.

Low voltage from 0 to 30 voltsDC / 0 to 15 volts AC

Intermediate voltage from 30volts or greater to 60 volts DC / 15volts or greater to 30 volts AC

High voltage any voltagegreater than 60 volts DC / 30 voltsAC

Note: Presently there are no industry standards to identify intermediate voltage. GM haschosen the color BLUE for this cable color.


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Key Hybrid Components

This illustration shows the location of the key 2008 GMC Yukon & Chevrolet Tahoe Two-mode Hybrid vehiclecomponents.

Hybrid Battery(inside vehiclecabin)

Drive Motors /Generators

Drive Motor /GeneratorControl Module

(under hood)

High Voltage CablesHybrid BatteryManual Disconnect(inside vehicle cabin)

300 Volt AirConditioningCompressor


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Key Hybrid Components (cont.)

The 2008 GMC Yukon & Chevrolet Tahoe Two-modeHybrid Vehicles use a conventional internalcombustion engine coupled with an ElectronicallyVariable Transmission (EVT) that includes two 60Kilowatt electric motors to efficiently power the vehicle.

Note: All high voltage cables used in Two-modeHybrid models are colored orange for easyidentification.

Conventional Engine with anElectronically Variable Transmission(EVT)


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The Electronically Variable Transmission (EVT)contains two 60 Kilowatt motors / generators that areutilized to:

Propel the vehicle

Generate / recapture energy

Start the Internal Combustion Engine (ICE)

Motors / Generators


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The Drive Motor / Generator Control Module performs the following operations:

Inverts 300 volts DC to AC for vehicle propulsion

Inverts 300 volts AC to DC for Hybrid battery recharging Provides 300 volts to Air Conditioning Compressor

Converts 300 volts DC to 42 volts DC for the Electronic Power Steering (EPS) system operation

Converts 300 volts DC to 12 volts DC for conventional 12 volt accessory operation

Note: Orange wiring is used to indicate high voltage. Blue wiring is used to indicate intermediate voltage.


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Key Hybrid Components (cont.)A Nickel Metal Hydride (NiMH) 300 volt Hybrid batteryis enclosed in a metal case located under the secondrow, rear seat sub-floor. This 300v Hybrid batterysupplies and stores energy for the vehicle.

300v Hybrid BatteryManual Disconnect


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A hood ajar switch is part of the hood latch andprevents Auto Stop Mode from occurring if the hood ofthe vehicle is open.

If the hood is opened while the vehicle is in Auto Stop

Mode, the engine will restart.

Note: The hood ajar switch will NOT prevent currentflow through the 300 volt electrical system.


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Approaching a Two-mode vehicle in AutoStop Mode:

If you approach a Two-mode Hybrid vehicle operating

in Auto Stop Mode, it may appear the vehicle isturned OFF, or the engine has stalled. Auto StopMode occurs under many conditions, including whenthe vehicle is in Park, Neutral or Drive and may lastfor several minutes. While in Auto Stop Mode theengine may restart without warning. Any of thefollowing conditions will cause the engine to restart if

the vehicle is in Auto Stop Mode:

The hood is opened

The shift lever is moved to Manual or Reverse

The 300v Battery charge becomes too low

Engine temperature drops too low


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Approaching a Two-mode vehicle inElectric Vehicle (EV) Mode:

While operating in Auto Stop Mode, the Two-Mode

Hybrid is also capable of propelling the vehicleelectrically. Referred to as Electric Vehicle (EV) Mode,this mode allows the vehicle to be propelled at speedsup to 25 mph, (40 Kp/h) while the engine is notrunning. Without depression of the accelerator pedal,just enough energy is provided by the electric motorsto allow the vehicle to creep slowly forward when inDrive. This operation is similar to a Non-Hybrid vehiclethat has an idling engine. Depressing the acceleratorpedal allows the vehicle to propel forward, anddepending on pedal depression, could also result inthe starting of the engine.

Perform the disabling 12v power procedure to ensure

that all vehicle propulsion modes have been disabled.


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The contactors inside the Hybrid battery aredesigned to open if one or more air bagsdeploy. This causes an interruption of the300 volt electrical system and discontinuescurrent flow in the high voltage cables.

This vehicle may have dual-stage airbagsand the appearance of deployed airbagsdoes not ensure that all parts of the airbagshave deployed.

Therefore, disabling 12 volt power isessential to ensure personal safety even if

the airbags in the vehicle appear to havebeen deployed. After disabling 12v power,wait at least 10 seconds to allow any un-deployed air bag reserve energy todissipate.

Air Bag Deployment


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1. Turn the ignition key to theOFF position.

2. Remove the 12 volt (+)positive battery cable fromthe battery post. Ensure the

terminal cannot contact thebattery post.

- OR -

If the ignition key is notaccessible, disconnect the12 volt positive (+) batterycable (located in the left,front underhood area).

Cut all three exposed 12vpositive cables. The cablesare identified by the yellowFirst Responder labels.

Note: After disabling 12v power,wait at least 10 seconds toallow any un-deployed airbag reserve energy todissipate.

To disable 12v power you must:

Note: The 12 voltbattery cableshave lever type,quick releaseterminals.


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GM has implemented the labels shown here to help First Responders safely disable the vehicle in anemergency situation.

First Responder Labels


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If accessible, you can minimizethe potential for 300v current

flow by removing the manualdisconnect lever from the 300volt Hybrid battery. The hybridbattery is located under thesecond row, rear seat sub-floor.

High Voltage ManualDisconnect

DANGER: The manual disconnect lever is designed tofacilitate servicing of the vehicle. The energy potential withinthe 300v battery cannot be disabled. Even with thedisconnect removed, assume the high voltage cables andcomponents contain high voltage. If the 300 volt battery isexposed, it should only be handled by a properly trainedtechnician - Otherwise, serious injury or death may occur.


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DO NOT CUT HERE. Under vehiclearea near passenger side framerail contains high voltage 300 voltelectrical cables.

DO NOT CUT HERE.Two-mode Hybridbattery has 300 voltelectrical potentialat all times.

DO NOT CUT HERE.Roof rails betweenthe windshield andD pillars (rearpillars). Side impactair bags.

Vehicle DO NOT CUT ZONES

Do NOT cut the:

Area near the passenger side framerail. High voltage 300 volt wiring isrouted near the frame rail on thepassenger side of the vehicle.

Roof rails between the windshieldand D pillars (rear pillars). 2008GMC Yukon & Chevrolet Tahoe Two-mode Hybrid vehicles are equippedwith side impact air bags.

Two-mode Hybrid battery. The Two-mode Hybrid battery has 300 voltelectrical potential at all times.

DO NOT CUT HERE.Side curtain air bags(with optional thirdrow seat)

WARNING: Do NOT cut into thevehicle until the 12v electricalsystem has been deactivated.

Cutting into the vehicle prior todisconnecting and isolating the12v electrical energy sources maycause air bag deploymentresulting in serious injury.


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Neutralizing a Battery Leak

The Nickel Metal Hydride (NiMH) battery containsPotassium Hydroxide and if a leak is detected, a mixtureof Borax and water, or a Class D fire extinguishershould be used to neutralize the spill.

Refer to your MSDS sheet for more information.


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Copyright 2007, General Motors Corporation

Conclusion

We are serious about making your job assafe as possible.

As you have seen, certain differences existbetween the 2008 GMC Yukon & ChevroletTahoe Two-mode Hybrid vehicles andconventional vehicles. These differencesrequire forethought when approaching anemergency situation concerning these Two-mode Hybrid vehicles.

We are confident the information containedin this guide will prove useful as you prepareto assist those involved in an emergencyevent.

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GMC Yukon and Chevy Taho Two-Mode