Monday, July 13, 2020

How to deactivate (or activate) neutral control

If you have a Volvo with Aisin AW55-50/51 automatic transmission, you may or may not have a function activated named "neutral control" (NC). This function is used for both earlier and later versions of the P2's.

If NC is activated, the transmission will automatically put itself in neutral, when you are holding the foot on the break pedal and the car has stopped. As soon you let go of the break pedal the transmission shifts back to drive.


Why use it?


Maybe some of the intention was for lowering the emissions? If you drive in cities, NC may lower your fuel consumption. If you have a trouble with vibrations when idling, NC may reduce vibrations. It may be that NC is mainly used together with diesel engines, because they generate more vibration.


Why not use it?


NC uses about a small second to engage to drive. If you quickly move your foot from the brake to the accelerator, your may rev up the engine before the transmission is engaged. This would be the same as moving the gearstick from N to D while revving the engine. Not a good feeling, and it will hurt the transmission.

As the transmission solenoids get old and contaminated, shifting between neutral and drive may get slower and more harsh. Normally it may not be a big problem, however if your transmission keeps switching between neutral and drive all the time, this will become very noticeable.

Overall I believe the NC will shorten the lifespan of the transmission. It makes the transmission work more, and every clutch engagement will shorten the lifespan of the clutch plates. Keeping the transmission in drive while the car is stopped will not wear the gearbox. It will only make the car use a bit more fuel.


How can I deactivate the neutral control?


Volvo made a configuration change available for removing NC. It was intentionally made for D5 cars from 2002-2003. However this also works for later models. You don't need a full software upgrade. This is just a small change in the car's configuration. Go to a Volvo dealer and order the following configuration update:

30646691 Neutral Control RE

If you for some reason want to enable the NC you have to order the following configuration update:

30646690 Neutral Control AP


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