The Variable Effort Steering (VES) system or MAGNASTEER® varies the amount of effort required to steer the vehicle as vehicle speed changes. At low speeds, the system provides minimal steering effort for easy turning and parking maneuvers. Steering effort is increased at higher speeds to provide firmer steering (road feel) and directional stability. VES works in parallel with the base torsion bar in the power steering system.
The VES control module communicates on the high speed bus and uses vehicle speed and the steering wheel angle speed to command a current that is most appropriate for each speed to the VES actuator in the steering rack and pinion. The actuator is a variable electromagnetic actuator, which consists of one multiple-pole ring-style permanent magnet, with a pole piece, and an electromagnetic coil assembly on each side. By commanding currents between -3 to +3 Amps through the coils the steering effort will be adapted to the vehicle’s speed.
At lowest speed, around 5 km/h (3 mph) the coils are polarized in such a way that the magnetic forces are repelling each others and hardly any effort is required to turn the ring magnet between them.
At mid speed, around 70 km/h (45 mph), no current is sent through the coils and steering is assisted by hydraulics only. At high speeds the coils are polarized in such a way that the magnetic forces are attracting each others and high effort is required to turn the ring magnet between them.
The VES control module communicates on the HS GMLAN bus.
The VES control module has the ability to detect malfunctions in the actuator. Any malfunctions detected will cause the system to ramp to zero amps. Steering will be assisted by hydraulics only and a DTC is set.
Special Tools and Equipment
Service Publications Ordering Information
Service Manuals
Service Manuals have the diagnosis and repair information on the engines, transmission,
axle, suspension, brakes, electrical, steering, body, etc.
Service Bulletins
Service Bulletins give additional technical service information needed to knowledgeably
service General Motors c ...
Collision Repair
Specifications
Point-to-point measurements are for reference only. All measurements are
given in millimeters. Use these measurements for diagnosing
and estimating. Point-to-point measurements are duplicated with tram bar
pointers set at equal lengths. All die marks, holes, slots, and
fast ...
Shifting out of Park
This vehicle is equipped with an automatic transmission shift lock control system.
The shift lock is designed to:
• Prevent ignition key removal unless the shift lever is in P (Park) with the shift
lever button fully released.
• Prevent movement of the shift lever out of P (Park) unless the ig ...