Cadillac CT6 PLUG-IN Delivers Efficient Performance

The new 2017 Cadillac CT6 PLUG-IN (Fig. 1) is a new type of hybrid vehicle that delivers added performance with an efficient powertrain. The turbocharged 2.0L 4-cylinder engine (RPO LTG) and hybrid electric variable transmission (RPO MRD) combine with a lithium-ion high-voltage battery to offer a hybrid powertrain capable of 31 miles (50 km) of electric range and a 0-60 mph (0-97 km/h) time of 5.2 seconds.


Fig. 1


EV Mode


The CT6 PLUG-IN works to provide the most efficient use of both propulsion power sources — the 2.0L turbocharged engine and the high voltage battery. (Fig. 2) When fully charged, the high voltage battery is the dominant propulsion power source and the engine will turn on occasionally to provide supplemental power.)


Fig. 2


The vehicle operates in EV mode under light or moderate driving conditions for approximately 31 miles (50 km) and up to speeds of 78 mph (126 km/h). Under aggressive acceleration, the engine will turn on to assist the high voltage battery. The engine will turn off and EV operation will resume once the vehicle is driven under light or moderate driving conditions again. The EV Operation Gauge on the instrument cluster indicates when the engine will turn on. (Fig. 3)


Fig. 3


When the high voltage battery is depleted, the engine is the dominant propulsion power source and the high voltage battery will provide only supplemental propulsion power. The Total Power Gauge shows the current source of power.


The high voltage battery will store enough energy to provide some hybrid/EV driving or supplemental power. Full EV driving can only resume if the vehicle is plugged in to charge. The Battery Gauge shows the high voltage battery state of charge. When the gauge reads empty, the vehicle should be plugged in to charge the high voltage battery and to allow maximum EV operation again.


Drive Motor Battery System


TIP: Technicians must be fully trained to service the CT6 PLUG-IN. This includes completing all hybrid training. Technicians also must follow all safety procedures and have Personal Protective Equipment (PPE) and up to date certified Class 0 HV Isolation Gloves.


The high voltage hybrid/EV battery is installed from beneath the vehicle, into the rear storage compartment. (Fig. 4) The battery energy control module, a current sensor, and the high voltage contactors are located within the hybrid battery assembly.


Fig. 4


The high voltage battery contains 192 individual lithium-ion cells. Every two cells are welded together in parallel for a total of 96 cell groups, which are electrically connected in series. The battery cell groups are joined to form three distinct sections. The battery sections also contain two temperature sensors. Diagnostics and system status are communicated from the battery energy control module to the hybrid powertrain control module 2 through serial data.


Other components (Fig. 5) of the Drive Motor Battery System include:

  1. S15 Manual Service Disconnect
  2. T18 Battery Charger
  3. K10 Coolant Heater Control Module
  4. K1 14V Power Module
  5. T6 Power Inverter Module
  6. G1 A/C Compressor
  7. C4B Hybrid/EV Battery Section 2
  8. C4C Hybrid/EV Battery Section 3
  9. A28 Hybrid/EV Battery Contactor Assembly
  10. C4A Hybrid/EV Battery Section 1
  11. K16 Battery Energy Control Module


Fig. 5


Parts Restrictions


The following components are on TAC Restriction to assist the dealership during diagnosis as well as to gather valuable feedback:

  • Drive Motor Battery (high voltage battery)
  • Hybrid Powertrain Control Module 2 (HPCM2)
  • 4EL70 Hybrid Transmission
  • CT6 Drive Motor Power Inverter Control Module (PIM)
  • Accessory Power Module (APM)
  • Drive Motor Battery Charger (OBCM) and Charge Receptacle


Cooling Systems


The CT6 PLUG-IN is equipped with three fully independent cooling systems.


The hybrid/EV electronics cooling system is dedicated to cooling the power electronics components — including the power inverter module, battery charger, and the power module — using the auxiliary radiator, engine control module inputs, radiator fans and hybrid/EV electronics coolant pump.


The high voltage battery is cooled and heated with pre-mixed DEX-COOL. Only use GM pre-mixed DEXCOOL, as it contains deionized water required for the high voltage battery and power electronics cooling systems. Use of any other coolant could result in potential Loss of Isolation DTCs.


A refrigerant/coolant heat exchanger (chiller) and the A/C compressor cools down the high voltage battery. A high voltage heater inside the high voltage battery can also heat the coolant entering the high voltage battery when needed.


The passenger compartment heater system uses the engine radiator, the auxiliary heater coolant pump, passenger compartment heater coolant control valve, high voltage coolant heater control module and a heater core to provide warm cabin air.


2.0L Turbocharged Engine


The 2.0L turbocharged 4-cylinder engine (Fig. 6) is designed for greater efficiency and power. The turbocharger generates up to 20 pounds (138 kPa) of boost and its twin-scroll design helps optimize the usable power from the engine. The engine produces 265 horsepower and 295 lb.-ft. of torque.


Fig. 6


Electric Variable Transmission


The new 4EL70 transmission (Fig. 7) is a fully automatic, rear wheel drive, electric variable transmission (EVT). It includes an input shaft, three stationary and two rotating friction clutch assemblies, a hydraulic pressurization and control system, an electric fluid pump, three planetary gear sets, and two electric drive motors. An external torque dampener, bolted to the engine crankshaft, is splined to the transmission input shaft.


Fig. 7


The hydraulic system includes a high pressure electric fluid pump driven by an electric motor supplied with high-voltage current from the power inverter module. The electric pump maintains working pressure and control of the clutches when the engine is on and when the engine is off.


The three planetary gear sets, electric motor-generators, and other clutches together provide all-electric propulsion, electric variable hybrid transmission ratios, and fixed mechanical transmission ratios. (Fig. 8)


Fig. 8




The Regen-on-Demand system enables the driver to control energy regeneration using the steering wheel paddles. Regenerative braking takes some of the energy from the slowing vehicle and turns it back into electrical energy, which is stored in the high voltage battery.


Regen on Demand allows the driver to increase the amount of deceleration provided by regenerative braking by pressing the paddles on the back of the steering wheel. It can be used during sporty driving and when descending hills to slow the vehicle. It also enables one-footed driving using the accelerator pedal and the selected deceleration level, which can be convenient in stop-and-go traffic. Select a deceleration level from M4 (fastest) to M1 (slowest) using the shift lever and the paddles to adjust the creep speed.


Information Displays


Several information displays are available on the infotainment system that provide an overview of hybrid operation. Select the Green Leaf Energy icon on the infotainment Home page and then touch the Flow, Charging, or Info icon. (Fig. 9)


Fig. 9


The Power Flow screen indicates the current system operating conditions, showing the power flow between the high voltage battery and engine through the transmission.


The Charging screens show the Charge Limit and Charge Mode status.


The Energy Info screens show the energy use (electric and gasoline) since the last time the high voltage battery was fully charged as well as how the energy was used.


High Voltage Battery Charging


The high voltage battery pack capacity is 18.4 kWh, but by design, only approximately 75% of the battery is usable to power the vehicle. The battery pack requires approximately 13–17 kWh to fully recharge, depending on temperature and battery condition. (Fig. 10)


Fig. 10


The minimum electrical circuit requirements for charging the vehicle are 120 volts/15 amps or 240 volts/20 amps. The charging times vary, but it will take approximately 4.5 hours to fully charge using a 240 V, 16 A charging station or approximately 20 hours using the default setting of 120 V, 8 A with the portable charge cord. (Fig. 11)


Fig. 11


The vehicle can be programmed for three charging modes: Immediately, Delay Charge Based on Departure Time, and Delay (Electric Rate and Departure Time).


Charging settings also can be saved for the vehicle’s home location. These settings will be used whenever the vehicle is parked at its home location. The settings can be changed in the Energy menu by selecting Settings on the infotainment system.


The charging indicator on top of the instrument panel (Fig. 12) shows the current state of the charging process.

  • Short Flashing Green Light – The vehicle is plugged in but the battery is not fully charged. The flash rate increases from one to four flashes as the battery charges.
  • Long Flashing Green Light – The vehicle is plugged in but the battery is not yet fully charged. Battery charging is in Delay Mode.
  • Solid Green Light – The vehicle is plugged in. The battery is fully charged.
  • Solid Yellow Light – The vehicle is plugged in but not charging.
  • No Light – The vehicle is not plugged in or there is an issue with the portable charge cord or the electrical outlet.


Fig. 12




To fill the fuel tank, press the fuel door button on the driver’s door. The Wait to Refuel message will display on the Driver Information Center. When the Ready to Refuel message is displayed, the fuel door will unlock. Press and release the rear edge of the fuel door to open it.


Special Tools


The following new tools were released for the CT6 PLUG-IN.


– Thanks to Sherman Dixon, Blake Streling and Keith Newbury

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