Allison Transmission & Output Speed Sensor Fault Code 2511

[Dr4Film]

Back early in March while on our trip bringing the 2006 Dynasty back home from Salt Lake City, I had one morning where the transmission threw a 2511 fault code which is an Output Speed Sensor Failure. Somehow, I got it to clear and never had another incident until last Friday. That's when I wanted to have the Dash AC evacuated and recharged with dye, but I could not drive the coach there as the transmission was again stuck in first gear with a Fault Code of 2511.

I called the Allison shop in Jacksonville to see if they may have an Output Speed Sensor for the transmission. They stated that they need the serial number. I attempted to contact REV which I will never do again as they are the WORST people to deal with when it comes to a Monaco coach.

So, I decided to crawl under the coach to get the necessary information.

While under there I called the Allison shop in Jacksonville FL and talked with a tech who helped me with finding the part number for the Output Speed Sensor plus she gave me specific instructions on how to remove the connector for the sensor. I did accomplish that task, cleaned up the connector and the sensor electrical connectors with electrical contact cleaner plus sprayed both ends with WD40.

Plugged it all back together and took the coach for a test drive.

All is now good with my Output Speed Sensor and my Allison Transmission.

The part number happens to be 29544139 for my transmission, $127.94. I will hold off on purchasing one as the cleaning may do the trick, permanently.

What appears to be happening is the small low voltage contacts will get corroded ever so slightly then will not pass the voltage like it should causing a 2511 fault code. Cleaning them with contact cleaner and a small amount of WD40 as suggested by Van WIlliams did the magic on the connector.

I hope to never have any more problems with that specific fault code.

[jacwjames]

Richard,

For future reference, where is the output shaft sensor located on the transmission, I assume it's fairly easy to get to.

[Dr4Film]

Jim,

It's called the Output Speed Sensor. There is an Input Speed Sensor and an Output Speed Sensor.

The location of the Output Speed Sensor is on the end of the Allison Transmission case that is attached to the driveshaft. It is around the 4 o'clock position.

There is a grey clip that needs to be removed first which then allows you to press on the button to release the connector from the sensor. The sensor is held into the case with one bolt. The connector is a weather seal type connector.

Hope this helps!

[jacwjames]

Clear as day

Thanks

[dl_racing427]

21 hours ago, Dr4Film said:

Back early in March while on our trip bringing the 2006 Dynasty back home from Salt Lake City, I had one morning where the transmission threw a 2511 fault code which is an Output Speed Sensor Failure. Somehow, I got it to clear and never had another incident until last Friday. That's when I wanted to have the Dash AC evacuated and recharged with dye, but I could not drive the coach there as the transmission was again stuck in first gear with a Fault Code of 2511.

I called the Allison shop in Jacksonville to see if they may have an Output Speed Sensor for the transmission. They stated that they need the serial number. I attempted to contact REV which I will never do again as they are the WORST people to deal with when it comes to a Monaco coach.

So, I decided to crawl under the coach to get the necessary information.

While under there I called the Allison shop in Jacksonville FL and talked with a tech who helped me with finding the part number for the Output Speed Sensor plus she gave me specific instructions on how to remove the connector for the sensor. I did accomplish that task, cleaned up the connector and the sensor electrical connectors with electrical contact cleaner plus sprayed both ends with WD40.

Plugged it all back together and took the coach for a test drive.

All is now good with my Output Speed Sensor and my Allison Transmission.

The part number happens to be 29544139 for my transmission, $127.94. I will hold off on purchasing one as the cleaning may do the trick, permanently.

What appears to be happening is the small low voltage contacts will get corroded ever so slightly then will not pass the voltage like it should causing a 2511 fault code. Cleaning them with contact cleaner and a small amount of WD40 as suggested by Van WIlliams did the magic on the connector.

I hope to never have any more problems with that specific fault code.

Grote, the manufacturer of truck lights and connectors, makes a gel designed to keep water out of connectors and prevent corrosion.
I've also used Co-Ox like you use on aluminum wiring feeding service entrance panels.  Either should last longer than WD40.

Edited May 4, 2022 by dl_racing427

[Skipjack]

Richard

Sounds very similar to my issue, but it happened very infrequently. 

Did your problem have symptoms as described below? (2003 Holiday Rambler, w/Allison Transmission 2000 MH with Cummins 5.9L)

Last year:

I have had this happen to me three or four times in the past six months.

When first starting out on a drive, the speedometer would read way too high (like 80mph when I am only driving about 20), and the transmission not shifting.

What I did to resolve this issue was to pull over, turn the engine off, and then restart. The problem went away.

When I am underway without the speed increase and have no issue. I have a steady speed readout on my speedometer.

When I have the problem, I know right away. 

I don't have a means of reading the engine or transmission codes, so I am unsure of what the problem actually is at this point.

NOW:

I since replaced the output speed sensor a few weeks ago, and have not had the issue since.

However, this happened so infrequently that I am not totally sure it is gone for good.

crossing my fingers

 

thanks

Kevin Atkins

[Dr4Film]

Kevin,

I did not experience any of the symptoms you have described above. When the fault occurred each time, the transmission will be locked in first gear and it throws a 2511 fault code that can be read on the Allison Shift Pad.