System, Stop-Start: Description

The Engine Stop/Start (ESS) 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 ESS function.

• Advanced Glass Mat (AGM) Battery with High Durability Battery Cables  - The AGM type battery and the high durability cables are capable of withstanding the increased cycling that a ESS vehicle will experience.
• Generator  - A 220a generator that is up-sized specifically for use with the ESS system.
• High Durability Starter  - This is a modified starter used for the ESS system. Changes are hardened gears with lead in chamfer, a spring pinion (Diesel), reinforced castings, a higher power motor, long-life brushes, precision bearings and motor shaft.
• InRush Current Relay  - This component works in conjunction with the VSM in order to prevent voltage dips.
• 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.
• Powertrain Control Module (PCM)  - The PCM monitors conditions for ESS.
• Transmission Neutral Sensor (MTX Only)  - This is located on the transmission selector cable.
• Voltage Stabilization Module (VSM) 

  - This component is required to maintain system voltage during ESS events. This also provides a buffer for the vehicles Electronic Control Units (ECU) when battery power is being sent to the starter for cranking.

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 systems include the most basic conventional diagnostic methods, to the more sophisticated On-Board Diagnostics (OBD) built into the 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).