System operation and circuit allocation

SYSTEM OPERATION

On this vehicle, the steering is assisted by an electric motor mounted on the steering column, depending on driver input. This driver input is measured by a torque sensor, which measures the effort applied by the driver to the steering wheel, and a column angle sensor. Assistance is provided by an electric motor that applies a greater or lesser torque to the steering column, in one direction or the other.

The ECU controls this assistance according to several vehicle environment parameters, including vehicle speed.

PULL COMPENSATION

In addition, the vehicle pull to the right or to the left is compensated by the electric power steering motor.

This motor can apply a constant or variable (self-adaptive) correction to the steering so that the vehicle does not drift to the left or right when driving straight ahead.

Note: When the ECU detects a fault, the level of assistance may be modified, depending on the severity of the fault.

Incorrect or missing vehicle speed information results in assistance equal to that at 40 km/h.

Note: Depending on operating conditions and on work carried out on the vehicle before ignition is switched on, power assistance may take some time to come on after the engine is started, for example after a battery disconnection or a power interruption.

Diagnostic warning light activation strategy

Service warning light flashing slowly at 2 Hz: the electric power steering system is in diagnostic mode.

Service warning light flashing rapidly at 8 Hz with the message "steering to be checked": steering wheel angle not calibrated and not indexed.

"SERVICE" warning light on steady with "steering to be checked" displayed on the instrument panel: invalid information received by the ECU.

• assistance equal to that at a speed of 40 km/h if vehicle speed information is absent or invalid,
• invalid steering angle sensor information: steering angle sensor not calibrated (no active reminder).

"STOP" warning light on steady with "steering fault" displayed on the instrument panel: fault in the system to be diagnosed. Contact your Techline.

Steering angle sensor indexing and initialisation

Indexing of the sensor is essential for its learning. Ignition ON is not required for this operation. This indexing becomes effective once the steering wheel has been turned more than a quarter turn to the left, then a quarter turn to the right.

Steering angle sensor initialisation takes place after ignition is switched on. The sensor is not initialised until the steering wheel has been rotated to the left or to the right. If this rotation is not carried out, the steering wheel angle value will be given with a difference of ±1.2 degrees compared with the actual angle.

Once the sensor is initialised, this value will be given with 0.1 degree accuracy.