Principle Of Operation

Control logic (example E38) includes:

• Servotronic control electronics active with KL R being switched "ON" - ensure no delay in operation if engine is started and vehicle is immediately driven.
• Plausibility check for speed signal - the control electronics monitor both the Speed signal "A" from the IKE and the vehicle speed signal on the K-Bus.
• The ability to detect both acceleration and deceleration from the two speed signals - the speed signal from the IKE is updated every two seconds.
• The servotronic assist is reduced gradually when the vehicle is under acceleration.
• The servotronic assist is adopted to the lower direct reading during decel or braking.

Electric/electronic failures with the servotronic system will result in the following:

• Power/electronic failure of the control module or solenoid - steering assist the same as high speed driving (increased effort).
• Vehicle speed signal missing - control module retains the assist mode in effect when the speed signal was lost.
• Speed signal implausible - steering assist the same as high speed driving (increased effort).

The GM also provides the diagnostic "gateway" to the Servotronic status and "Component Activation" via the DISplus/GT-1.