Stop Start System

The Stop-Start system automatically stops and starts the engine when certain conditions are met to improve fuel economy and lower CO2 emissions.

The primary input for manual transmission vehicles to an autostop is zero vehicle speed with the transmission in neutral and the clutch pedal released, while the primary input to autostarting is depression of the clutch pedal. The primary input for an automatic transmission vehicle to gain an autostop is zero vehicle speed with the brake pedal depressed, while the primary input to autostarting is release of the brake pedal. Many secondary inputs determine if it is acceptable to autostop and autostart. A number of devices on the vehicle are added or improved to support the Stop-Start function.

• Automatic Transmission 

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  • New thermal management system for maintaining optimum operating temperature
  • Vehicle launch control coordination with engine and brake system
• Batteries - Vehicle Battery and Cranking Battery 

  - During cranking, both batteries work together to provide a starter load. During a stop/start event, the two batteries work separately:

  • The smaller vehicle battery supports the vehicle Ignition off electrical load.
  • The Larger cranking battery supports the re-start event.
• Door Ajar Switch 

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  • The driver door ajar switch for stop/start vehicles has two diagnostic resistors installed in the latch assembly circuit. This resistor allows the BCM to detect an open or shorted condition in the circuit.
• Engine 

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  • Lubrication system and wear components to manage increased stop and start frequency.
• Engine Mounts 

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  • Modified based on starter packaging. This may be unique for every engine and vehicle.
  • Optimized for NVH given increased engine stop and start frequency.
• Electronic Stability Controls 

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  • Provides brake controls using Hill Start Assist (HSA) during autostart and transmission engagement transition to prevent vehicle movement while in an autostop condition during the transition from brake pedal to accelerator pedal. Brakes to be released commensurate with torque request and torque capacity
  • Ensure module compatibility with cranking during HSA function (voltage drop, etc.)
  NOTE:

  When the ESC system is deactivated (OFF) the LED light in the button will be illuminated.

• Flywheel / Drive Plate 

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  • Revised ring gear with chamfered, hardened gear teeth to improve starter pinion engagement and reduced gear tooth wear
• Generator 

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  • Higher output alternator to provide greater charging capacity immediately following autostarts.
  • No requirement for voltage regulation on stop/start system.
• Intelligent Battery Sensor (IBS)  - The IBS is responsible for measuring the state-of-charge. It will also predict voltage and capacity (ah) for future crank events. The IBS is also responsible for measuring battery temperature and alternator voltage current.
• Instrument Cluster 

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  • Revised instrument cluster with stop-start specific graphics and IC messaging.
• Body Control Module 

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  • Modified Body Control Module (BCM) for communications and starter control.
• Hood Switch 

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  • To prevent an autostart while the hood is in a raised position, a secondary hood switch is added to provide redundant hood position sensing.
  • The secondary hood switch is wired to the PCM.
• HVAC Head Unit and Controls 

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  • Added control features to provide interior climate management.
  • Fan speed control adjusted during autostop.
  • Autostop inhibit and autostart request based on combination of interior temperature, sun loading and variation from temperature set point and/or ambient temperature. This may inhibit some autostops or reduce autostop duration.
• Powertrain Control Module (PCM) 

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  • Circuit board population for added inputs and outputs.
  • Stop-start coordinator added to manage all autostop and autostart activity.
  • Impact on torque, security, OBD and end of line diagnostics.
• HBC/ESC Vacuum Sensor 

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  • Switch in vacuum hose connector to initiate engine restart in case of low vacuum.
• Radio Head Unit and Integrated Center Stack 

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  • Added stop-start specific messaging and menu selections.
• Starter (High Durability) 

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  • Enhanced starter with increased life brushes, needle bearings, pre-loaded pinion gear spring and other changes to enhance longevity and improve NVH
  • Starter power increased to compensate for brush losses and to increase cranking speed
  • In-rush current reduction (ICR) device is required to achieve minimum system voltage drop requirements of critical modules and devices and autostop duration and frequency objectives. It is located on a bracket attached to the lower front of the engine, below the A/C compressor.
• Stop/Start Disable Switch 

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  • New hard switch located in the center stack switch bank.
    NOTE:

    When the Stop/Start system is deactivated (OFF) the LED light in the button will be illuminated.

The Battery, Starting, and Charging systems operate in conjunction with one another, and must be tested as a complete system. For correct operation of starting/charging systems, all components used in these 3 systems must perform within specifications. When attempting to diagnose any of these systems, it is important that you keep their interdependency in mind.

The diagnostic procedures used in each of these groups include the most basic conventional diagnostic methods, to the more sophisticated On-Board Diagnostics (OBD) built into the Powertrain Control Module (PCM). Use of an induction-type milliampere ammeter, volt/ohmmeter, battery charger, carbon pile rheostat (load tester), and 12-volt test lamp may be required.

Certain starting system components are monitored by the PCM and may produce a Diagnostic Trouble Code (DTC).