Operation - Vehicles With Stop/Start System (From 2014 My): Notes

WARNING: This page is about a different car, the 2015 Jaguar XF, 2014 Jaguar XF, and 2013 Jaguar XF. However, it is still accessible from the selected car via links, so may be relevant.

If the engine is rotating fast, the TSS motor is energized by a solenoid to increase the pinion gear speed. The second solenoid is energized and the pinion gear is moved forward to engage with the ring gear when the rotational speed of the ring gear and pinion gear are close.

When the engine is rotating slowly enough for the two gears to be connected, the pinion gear is first moved forward into engagement with the ring gear, and then the TSS motor is powered to restart the engine.

With the TSS, the pinion gear movement and motor rotation are separately controlled by the Engine Control Module (ECM) depending on the engine speed, and the engine can restart while it is still rotating. This provides an instant engine restart.

The TSS allows 'change of mind' scenarios, for example, when the vehicle is coasting to a stop and the engine speed is 400 RPM or less, and the driver releases the foot brake pedal to accelerate the vehicle again, the engine can be restarted.

At engine speeds of 250 to 750 RPM, the ECM uses the TSS motor to accelerate the pinion gear up to the engine ring gear speed and the pinion gear is then moved into engagement with the ring gear. This process take approximately 100 milliseconds.

At engine speeds below 250 RPM the ECM first engages the pinion gear with the ring gear and then operates the TSS motor to restart the engine. This process takes approximately 300 milliseconds.

The TSS motor is controlled by the ECM. The ECM controls two relays located in the Engine Junction Box (EJB); one for the motor and one for the pinion movement. When the ECM energizes the relays, battery power from the primary battery is supplied via a 350A fuse and the Dual Battery Junction Box (DBJB) to each relay in the EJB. The power passes through the relay contacts in the EJB to the TSS motor solenoids. The ECM can control the operation of each relay individually to control the TSS operation depending on engine operating conditions. Power from the primary battery is supplied via a 450A fuse direct to the TSS motor. Battery power is supplied to the TSS motor when the EJB operates the TSS solenoids.

The DBJB contains two relays which are controlled by the Dual Battery Module (DBM). The DBM monitors the vehicle electrical loads and will prevent the available electrical power to other vehicle systems being subjected to low voltages and use power from the secondary battery to ensure the other vehicle systems are unaffected by the vehicle restart. If the available battery voltage from either the primary and secondary batteries is too low, the DBM will inhibit the Stop/Start system.

Refer to Battery and Cables (Description and Operation).

The ECM has a low voltage strategy which will allow the starter motor to rotate the pinion gear at voltages as low as 4V. The pinion gear movement is disabled at voltages of less than 5 V. This can cause the pinion gear to engage with the engine ring gear and momentarily crank the engine, but if the voltage falls to below 5V, due to cranking the pinion gear may be disengaged. The ECM will stop the starter motor if engine rotation is not detected, however, the motor may run in a disengaged condition for 250 ms which will be audible.