I have c180 2012 . i walked 6000 km and there is vibration in car when speed is 15 km and this happen only when i leave the accelator ... i need to know what is the problem in car

It is HVAC 1fuse #39 in the rear fuse block ,this powers the on/off switch for cruise control ! Fuse Block - Rear Beneath the left rear seat. What engine does it have ? 4.2 L or 5.3 l There is no vacuum involved in the operation of the cruise control ! Your vehicle has electronic throttle control .
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at vehicle speeds above 40 km/h (25 mph). Steep grades may cause variations in the selected vehicle speeds.
The following are the main components of the Cruise Control System:
?€¢
The powertrain control module (PCM)

?€¢
The On/Off switch

?€¢
The Resume/Accel switch

?€¢
The Set/Coast switch

?€¢
The TCC brake switch

?€¢
The stop lamp switch

?€¢
The throttle actuator control (TAC) motor

?€¢
The vehicle speed sensor

Cruise Control Engaged
The cruise control system will engage and adjust the vehicle speed based on the activation of the following cruise control switches:
?€¢
On/Off

?€¢
Resume/Accel.

?€¢
Set/Coast

The cruise control switches are located on the multifunction/turn signal lever.
The powertrain control module (PCM) monitors the signal circuits of the cruise control switches in order to determine when to capture and maintain the selected vehicle speed. The PCM uses the throttle actuator control (TAC) module motor in order to control the vehicle speed. For further information on the TAC System, refer to Throttle Actuator Control (TAC) System Description in Engine Controls - 4.2 L.
Ignition positive voltage is supplied from the 10 ampere HVAC 1 fuse to the cruise control switch via the ignition 3 voltage circuit. When the normally open cruise control On/Off switch is turned On, the switch closes and the PCM detects a high signal voltage on the cruise control on switch signal circuit. When the normally open Set/Coast switch is pressed, the switch closes and the PCM detects a high signal voltage on the cruise control set/coast switch signal circuit. To engage the cruise control system, turn the On/Off switch On and momentarily press the Set/Coast switch. The PCM will confirm that the cruise control enable criteria has been achieved. The PCM will engage the cruise control system and record the selected vehicle speed. The PCM sends a class 2 message to the instrument panel cluster in order to illuminate the cruise control indicator. Pressing the accelerator pedal, while the cruise control system is engaged, will allow the driver to override the cruise control system in order to accelerate the vehicle beyond the current set vehicle speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override the current set vehicle speed via the Set/Coast switch and the Resume/Accel switch. When the cruise control system is engaged, pressing and holding the Set/Coast switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the Set/Coast switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily pressing the Set/Coast switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the Set/Coast is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). When the normally open Resume/Accel switch is activated, the switch closes and the PCM detects a high signal voltage on the cruise control resume/accel switch signal circuit. Activating and holding the Resume/Accel switch, when the cruise control system is engaged, will allow the vehicle to accelerate to a greater vehicle speed than the current set vehicle speed. When the Resume/Accel switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily activating the Resume/Accel switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the Resume/Accel switch is momentarily activated, with the maximum acceleration total of 16 km/h (10 mph) over the current set vehicle speed . Momentarily activating the Resume/Accel switch, after the cruise control system has been disengaged by pressing the brake pedal, will recall the previous set vehicle speed that is recorded in the PCM.

does it vibrate at highway speeds or sitting still at idle? the highway speed vibration could be tires out of balance. the idle speed vibration could be weak engine mount or idle speed too low.

well i would check tires balance and i would check drive line some time the center suport bearing gos out will make car vibrates hope this helps

if you google "grand vitara vibration" you will find a discussion board about the many many grand vitaras getting around with a vibration problem. I happen to be one of these people and am seriously thinking of selling the car after all the problems I have. It appears to be a drive train design fault which will cost a fortune to fix, believe me its not a tyre problem, ive had 4 wheel alignlents and balances and it never seems to fix the problem.Take it to a mechanic and let them have a good look at it.

check wheel bearings , loose ball joints steering idler arm...

you have a stripped and or binding speedometer cable or gear :)

Have a look at the transmission mount. Also look at the universal joints in the drive shaft.
If the transmission mount is bad or mushy it will allow the metal part of the mount to touch the crossmember causing a vibration.
A dry u-joint will also cause a vibration. Even if the u-joint isn't worn out or has visible play. Being dry will cause this. Are the u-joints factory? Do they have grease fittings on them? Have they been replaced? How many miles on them?
If the u-joints don't have grease fittings then they are most likely factory u-joints. Hope this helps. Good luck.

this needs a motor vehicle technician to lift vehicle and inspect the damage ,but it will not be cheap because i should imagine that the lower track control arm is damaged ,and the tyre is now running out of alignment which is caused by the above

I would start with the cheaper problem first, if you live in snow or mud county pull the tires look for mud, ice, then have your tires re-balanced. Not that try wheel aliment