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Understanding the AW 55-50 Neutral Control

Jerry Huerter - Diagnostician

Diagnostician - Jerry Huerter Jerry Huerter is an ASE certified Master Technician and has over 35 years of experience in the automotive industry. He is currently working at Certified Transmission’s Overland Park KS facility diagnosing vehicle problems. His years of experience make him a great asset to the company and its customers.

We recently had a 2001 Volvo S60 come into or shop with a smoked AW 55-50 transmission that needed to be replaced.

The AW 55-50 transmission has a feature that Volvo calls "Neutral Control". What it "Neutral Control" and what is its function? To tell you the truth, I wasn?t really sure, but below is what I was able to both find and figure out about it.

When coming to a complete stop in drive with your foot on the brake, the TCM waits 2 seconds before disengaging drive or shifting the transmission into neutral. This feature is designed to reduce emissions and to minimize any idle vibrations. When the brake pedal is released, this re-engages drive. This is a very smooth and seamless process that is never felt by the operator.

However, when replacing the transmission special attention and very specific directions must be followed to adapt the new unit to the car. If adaptation is not properly completed, then a very noticeable "thud" will be felt shortly after coming to a complete stop. When the brake pedal is released, a harsh engagement will also be present.

Volvo has published a TSB (TSB 43-38) that requires the use of their VADIS to put the car into Adaption Mode. Once this is hooked into the system, you can begin the adaptive learn and test drive.

After the transmission is in adaptive mode, the orange triangle in the center of the instrument cluster will flash just after a perfect shift is obtained. Volvo considers a perfect shift as one where the TCM has reached its adaption target for that particular shift. While in Adaptive Mode, you will experience all of the types of shifts listed in the TSB until the light flashes to tell you it was a perfect shift. When all the shifts are perfect you are done, the adaption is complete.

Does this sound like this might take awhile? Yes it does!

I understand that the last Snap-On scan tool update (11.2) included the updated software for the Volvo. Does anyone out there have the 11.2 update and can you tell us if it has the Volvo Adaptation Mode or do we need to take this one to a Volvo Dealer to have them do the Adaption relearn?