It's the overdrive engage button, which is like a 5th gear. It only engages when the gear lever is in 4th gear and it can be operated without depressing the clutch.
So that you don't shift the gear selector by accident
This button is for winter mode. The transmission will start in 3rd gear thus reducing wheel spin when starting from a stop in slippery conditions.
Volvo is a great technology in vehicles. Shift light indicator mean the indication given, that the vehicle is now comfortable to shift the gear. For Example, the Volvo car is moving on 60 mph and you are moving on 4th gear the shift light indicator will blink reminding now you can shift a gear further mean you can move by gear 5.
On a 1998 Ford Taurus ; On the column shift the overdrive button is on the end of the gear shift lever On the console shift the overdrive button is on the drivers side of the gear selector lever below the button you have to press to shift out of PARK
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To replace the shift lock button on a 2000 Volvo S40, start by removing the center console panel surrounding the gear shifter. This typically involves unscrewing screws and gently prying the panel away. Once exposed, disconnect the wiring harness from the old shift lock button and remove it from the assembly. Install the new button by reversing the process, ensuring a secure fit before reassembling the center console.
The button is located on the left side of the gear shift. (right under the main shift button)
4th gear
A common problem with alot of Volvo's is the Overdrive. Basically the high gear. If it wont shift into high gear it means that the "Overdrive" is activated and won't shift into high gear. You need to see if there is a little upwards pointing arrow on your Dashboard Cluster. If there is then you need to replace your Overdrive Solenoid.
I assume that is the button that allows you to turn off or turn on the overdrive for the transmission ( my Ford Explorer also has a button on the end of the gear shift lever for that purpose )
To change the gear shift in a 2004 Volvo S60, first ensure the vehicle is in "Park" and the ignition is off. Remove the trim around the gear shift by gently prying it up, then unscrew and disconnect any electrical connectors. Replace the gear shift assembly by reversing the process, ensuring everything is securely reconnected before reassembling the trim. Finally, test the new gear shift to ensure it functions properly.
The cause of the key sticking in the ignition, after the car is turn off. This is caused by the button on the gear shift knob, not coming out all the way or sticking.