Allison Transmission

Topic: Allison Transmission (Read 2058 times) previous topic - next topic

Allison Transmission

December 29, 2011, 10:41:42 pm

Today was a beautiful day here so we decided to take our coach out for a drive to exercise it. It has been in storage for approximately 2 months and I wanted to take it for a drive.

Everything was going well and I was driving around 60 or so in the interstate when I noticed it would down shift to gear 5 and then back to gear 6. This happened a few times and then I noticed the SERVICE light would briefly illuminate on the shift panel display.

When we stopped for a break, I checked the transmission diagnostics by pressing the up/down arrow keys simultaneously. It showed the oil level to be OK. I had the transmission oil changed this fall just before taking it to storage and used the synthetic.

I then pressed the up/down arrow keys a second time and got the following diagnostic code:

d1 21 23

According to the manual I have ( ), it lists the description as Throttle position sensor, failed high.

We turned around and drove back toward the storage location. On the return, it down-shifted from gear 6 to gear 5 and then back frequently and the speed dropped to around 55 mph instead of 60-65 mph. The SERVICE light illuminated various times again.

After we got the coach to the storage area, I checked the transmission diagnostic again and got the same indication. (Oil level OK the first time I pressed the up/down arrow keys, then when I pressed the up/down arrow keys again, I got the same code - d1 21 23).

Has anyone had this problem? If so, any idea what the problem is? Is it something I can troubleshoot further or is it something that will have to be checked out by the Allison shop?

Our coach is a 1997 U270 with the Cummins diesel and the 6-speed Allison transmission.

Thank you very much.

Re: Allison Transmission

Reply #1 – December 29, 2011, 11:17:15 pm

Quote from: ncaabbfan – December 29, 2011, 10:41:42 pm

Throttle position sensor, failed high.

Fortunately, I have not had that problem. If you are mechanically inclined, disconnecting the ground wire to the chassis battery and reconnecting might be worth a try. I'm not sure if that would remove the problem code from memory. If you are even more mechanically inclined, disconnect and reconnect as many of the connections on the transmission wiring harness as possible, looking for corrosion might be worth a try, before taking it to an Allison shop. I suppose you would have to drive it after doing the above to see if it helped. No idea where the sensor is located, but guessing either at the pedal below the floor or somewhere on the engine. Maybe someone else with more knowledge than me can give some advice.

Re: Allison Transmission

Reply #2 – December 30, 2011, 01:16:41 am

Saw someone posted a similar issue on iRV2. Their TPS was bad. Hope that's not the case for you!

"Service" message on Allison MD3060 display w/code 21 / 23 - iRV2 Forums

And another similar issue...

RV.Net Open Roads Forum: Class A Motorhomes: Allison MD3060P not shifting

Re: Allison Transmission

Reply #3 – December 30, 2011, 09:25:06 am

Morrris, These tramsmissions are really sensitive to voltage. If your batteries are not fully charged they can cause some weird Allision Problems, Make sure your have 12.5 Volts , then disconnect, reconnect the grounds on the chassis batteries and then clear the code and look again, IF you are lucky that may clear the code and reset ECU.
Any time mine is in storage for long period I have similar problem, mine is a 95 so yours may be different.
Good Luck
Gary B

Re: Allison Transmission

Reply #4 – December 30, 2011, 09:32:32 am

I second what Gary said. I had mine in storage outside and the battery was weak and I got that error on my 99.

Re: Allison Transmission

Reply #5 – December 30, 2011, 09:55:13 am

I don't have manuals handy, but there will likely be a mechanical connection between the throttle (likely at the engine end) and the Allison throttle position sensor. Start by verifying that it IS connected and moves freely as you move the throttle and that the electrical connection at the Allison throttle position sensor is clean and tight.

And, if indeed the Allison thinks you are at WOT (Wide Open Throttle) it will downshift. A temporary workaround is to be sure you are in ECONOMY MODE which will allow the transmission to stay in a higher gear, even at (what it thinks is) WOT.

Brett

Re: Allison Transmission

Reply #6 – December 30, 2011, 10:15:18 am

I had problem not shifting properly and spoke with King Controls he helped me diagnose with meter and had me remove a filter (part of King Control) and all shift problems endend.

Larry Bradley
1998 U270

Re: Allison Transmission

Reply #7 – December 30, 2011, 01:31:26 pm

Quote from: wolfe10 – December 30, 2011, 09:55:13 am

I don't have manuals handy, but there will likely be a mechanical connection between the throttle (likely at the engine end) and the Allison throttle position sensor. Start by verifying that it IS connected and moves freely as you move the throttle and that the electrical connection at the Allison throttle position sensor is clean and tight.

Brett

Thank you very much. Where is the Allison throttle position sensor located and how can I recognize it?

Is the throttle link an actual mechanical linkage or is it electronic?

Re: Allison Transmission

Reply #8 – December 30, 2011, 02:31:44 pm

Morris,

At least on the older series Allison electronic transmissions, there is a cable linkage to a chassis rail mounted electrical sender unit that translates mechanical movement into an electrical signal to the Allison ECM.

Look at the injection pump on the engine where the throttle comes in. Again, at least on the older ones, there is another cable that is perhaps 4' long that goes to it.

Please let us know what you find on yours.

And, again, make sure the electrical connection is clean and tight.

Re: Allison Transmission

Reply #9 – December 30, 2011, 02:40:03 pm

I want to thank everyone for the comments and suggestions. As soon as possible after the first of the year when we have a warmer day, we will go over and lift the coach up, block it and I will crawl underneath it to see what I can find. I hope it is a loose connection of some kind.

It seemed much worse yesterday on the return and specially on a section of highway that was extremely rough. I don't know if it was a coincidence or if the rough section of road contributed to it.

Thanks again I greatly appreciate everything.

Re: Allison Transmission

Reply #10 – December 30, 2011, 03:12:55 pm

Morris,

You should be able to see this area from either under the bed engine access and/or from the rear of the coach. I would start by lifting the bed.

Now, if you got some clothes for Christmas that you REALLY don't like and want an excuse to get them greasy, THAT is another story.

Brett

Re: Allison Transmission

Reply #11 – January 03, 2012, 11:21:16 pm

Quote from: wolfe10 – December 30, 2011, 03:12:55 pm

Morris,

You should be able to see this area from either under the bed engine access and/or from the rear of the coach. I would start by lifting the bed.

Brett

Is this area toward the front end of the transmission (under the foot of the bed) or along one side of the transmission?

Quote from: wolfe10 – December 30, 2011, 02:31:44 pm

Morris,

At least on the older series Allison electronic transmissions, there is a cable linkage to a chassis rail mounted electrical sender unit that translates mechanical movement into an electrical signal to the Allison ECM.

Look at the injection pump on the engine where the throttle comes in. Again, at least on the older ones, there is another cable that is perhaps 4' long that goes to it.

Please let us know what you find on yours.

And, again, make sure the electrical connection is clean and tight.

How can I recognize the chassis rail mounted electrical sender unit and the injection pump on the engine?

Re: Allison Transmission

Reply #12 – January 05, 2012, 10:47:19 pm

We went over to the coach today to do some checking on the wiring to the transmission. I did not start the Cummins engine at any time today.

I lifted up the bed and located a rectangular box with a can shaped device on one side of the rectangular box. It had the following on the end of the can shaped device:
Applied Motion Products, Inc
Stepping Motor
Part Number 5023-376
1.8 degree
4.7 V
B Class
1.8 Amp
Made in Taiwan Impedance Protected

The rectangular box has the following on it:
KC-2600
3303
CR-5797

An electrical cable goes into the rectangular box and a control cable (similar to the fuel control adjustment cable on a lawnmower) goes to the throttle on the Cummins engine.

My wife turned on the coach ignition and moved the accelerator pedal up and down. When the accelerator pedal was moved up and down, the rod portion inside the control cable would move back and forth and would rotate the throttle on the Cummins engine. I did not measure the length of the motion of the rod portion.

I presume this rectangular box with the can shaped device (stepping motor) is the transmission throttle position sensor. Is this correct?

4 or 5 rectangular electrical connectors are connected to cables going into the rectangular box. I checked each of these connectors and found each one to be tight and apparently securely connected. I pushed in on each individual wire and they seemed to be tight in their respective slot in each connector. So basically, I did not find anything that appeared to be incorrect in any of the connectors in the cables going to the rectangular box.

I crawled under the coach and found 2 or 3 large cables(?) connected to the transmission housing. Each cable is fairly large diameter and the attachment fitting was reasonable large. I checked each attachment fitting with my fingers and each was very tight.

I did find one single wire that came out of one of these large cables. This wire had a spade type connector on it and the connector slid onto a disc shaped fitting that is mounted on the transmission housing. This is on the driver side.

I removed the spade type connector from the disc shaped fitting and used a brass wire brush and knife blade to scrape the disc shaped fitting as well as inside the spade type connector. I slid the spade type connector back on the disc shaped fitting. I couldn't see the surface of the disc fitting or inside the spade type connector to see if there was any corrosion. So I do not know if this wire had any problems due to corrosion or not.

I also found two small wires connected to terminals on the transmission housing (on the passenger side of the coach) with what looked like ring type terminals. I tried to rotate and pull each of these two wires. I found each of these wire to be tight. I did not remove the ring connectors from the terminals since both seemed to be very tight.

The accelerator pedal in our coach is Williams.

I checked the voltage across the + and - terminals on each of the two chassis batteries. One read 12.36 V and one read 12.37 V.

I did see a small rectangular gray plastic cap hanging down from underneath the dash on the left side of the steering wheel. It had "Diagnostic Do Not Disconnect" molded in the plastic. It had what looked like a 2-prong jumper inside the plastic cap. I located a rectangular receptacle where the plastic cap was attached. The cap slid right on the receptacle and latched on. So it appears the 2-prong jumper slid into two of the receptacles. I have no idea what this is for nor do I have any idea when it was disconnected or who disconnected it unless it was disconnected when the Allison shop changed the transmission fluid just before putting it in storage this fall. Since it tightly latched on the receptacle, it had to be disconnected instead of falling off.

Unfortunately, I did not find anything that appeared to be an issue except possible the gray plastic cap with the two prong jumper.

Are there any other suggestions concerning things to check?

Thank you very much.

Re: Allison Transmission

Reply #13 – January 06, 2012, 09:29:58 am

Morris, A fully charged battery should read 12.6 volts, at 12.3 they are appreoaching discharge.
Gary B

Re: Allison Transmission

Reply #14 – January 06, 2012, 09:40:19 am

Voltage still not bad after 2 months in storage. I would make sure to start the genset and use the boost switch to ensure the batteries charge up a bit before relegating the alternator to do the charging once the engine starts. I also turn on the engine block heater to help the engine turn over easier when it's cold and also give the genset something else to "work" for.

Re: Allison Transmission

Reply #15 – January 06, 2012, 11:50:23 am

Quote from: ncaabbfan – January 05, 2012, 10:47:19 pm

I lifted up the bed and located a rectangular box with a can shaped device on one side of the rectangular box.

I think what you are describing is the King Throttle Control. You can read all about it here with some pictures. King Control Throttle and Cruise Control Issues

Re: Allison Transmission

Reply #16 – January 06, 2012, 12:53:06 pm

The throttle position sensor is often mounted on the back of the pedal.

Re: Allison Transmission

Reply #17 – January 06, 2012, 01:42:08 pm

Quote from: Gary Bouland – January 06, 2012, 09:29:58 am

Morris, A fully charged battery should read 12.6 volts, at 12.3 they are appreoaching discharge.
Gary B

Quote from: Peter & Beth – January 06, 2012, 09:40:19 am

Voltage still not bad after 2 months in storage. I would make sure to start the genset and use the boost switch to ensure the batteries charge up a bit before relegating the alternator to do the charging once the engine starts. I also turn on the engine block heater to help the engine turn over easier when it's cold and also give the genset something else to "work" for.

Is the recommended next step to charge up the chassis batteries to see if this resolves the Throttle Position Sensor error code on the transmission?

Quote from: Jerry Whiteaker – January 06, 2012, 11:50:23 am

I think what you are describing is the King Throttle Control. You can read all about it here with some pictures. King Control Throttle and Cruise Control Issues

Yes, after reviewing the article listed, the box I discussed is the King Throttle Control. In fact, the KC-2600 matched up with the number listed on the schematics.

Re: Allison Transmission

Reply #18 – January 06, 2012, 02:33:51 pm

For me, it's hard to tell what will not work properly wth low voltage. My speedometer odometer goes haywire if the voltage is too low. What I was stressing was the extra duty the alternator has to perform to charge very low batteries. But, for all I know the transmission selector/monitor lights as well as other sensitive electronics in the Allison can also go haywire with low voltage, as Gary B. mentioned earlier.

Re: Allison Transmission

Reply #19 – January 16, 2012, 10:22:30 pm

I wanted to give an update based on our experience today. It was another beautiful day here...69 degrees so I wanted to do some more checking on the TPS error code we had a few days ago.

Today, I first checked underneath the accelerator pedal. There is a device mounted underneath the pedal that has a shaft coming out the left side (when looking forward) of the device. The shaft has an arm mounted on it and the arm has a roller on the end. Apparently when the accelerator pedal is pressed down, the arm/roller causes the shaft to rotate. (I presume this device is the Throttle Position Sensor. Does this sound correct?)

I found a small cable (I believe 3-wires) coming out the bottom of the device. I unplugged this small cable and plugged it back in and fastened it in place.

I then removed the "L" shaped kick panel that fastens to the bottom of the black panel on the drivers side wall and that goes around in front of the steering column just in front of where the steering column goes through the floor. I found the Allison ECU mounted to the driver's side wall. There are 2 large connectors plugged into the forward edge of the Allison ECU. With the engine off, I unplugged one of these connectors and then re-inserted it in the connector. Then I did the same with the second plug.

I started the engine and could rev up the engine when I pressed down on the accelerator pedal or rotated the arm by hand.

I then followed the procedures to manually delete the transmission error code. I confirmed that all codes had been removed.

We then went for a drive. We drove 60-70 miles. I did NOT see the SERVICE light illuminate any at all during our trip. I did not experience any of the down shifting from gear 6 to gear 5 as we did on the previous trip. After we got back to the storage location, I checked the diagnostics. The oil level was shown as OK and NO error code(s) was/were displayed.

So I do not know if the problem has been corrected. All I know is after doing the few things listed in this post as well as scraping the connector and post a few days ago and then driving the 60-70 miles today, no error code(s) was/were set and I did not see the SERVICE light illuminate any.

Does any of this make any sense to anyone here?

Thank you.

Re: Allison Transmission

Reply #20 – January 17, 2012, 12:40:50 am

Additionally, each of the individual wires that plug into the 2 large connectors on the Allison ECU should be checked to be sure that each small wire is fully seated in the bigger plug.

Re: Allison Transmission

Reply #21 – January 30, 2012, 10:03:41 pm

I thought I would provide another status update.

It was another beautiful day (very windy, but beautiful) today. So we took the coach out for a drive today to exercise it and to see if there were any more error codes or issues with the transmission. We drove around 147 miles round trip today and took the same route we took in late December when we had the down shifting, the SERVICE light was illuminated occasionally and error codes were displayed.

I drove 60-almost 70 mph on the interstate today.

Going out, I did not press the MODE button. I understand this left the transmission in the default setting. Just before starting back to the storage location, I did press the MODE button so the return trip was with the MODE ON (display shows MODE ON).

When we got back to the storage location and while the engine was cooling down, I checked the transmission diagnostics. It displayed OL OK and had no (0) error codes displayed. I did not experience any issues with the coach down shifting any at all today unless I was slowing down and I did NOT see the SERVICE light illuminate any today. So far, we have not had any down shifting problems or any error codes displayed and I have NOT seen the SERVICE light illuminate since I disconnected/reconnected the small cable that connects to the device mounted underneath the accelerator pedal, the two large cables that connect to the Allison ECU and scraped the one connection under the transmission.

So I do not know if the problem has been resolved, but it has not reappeared since the drive in late December.

I am presuming that if it was an actual problem, it would have resurfaced today or the drive a few weeks ago unless it is an occasional intermittent problem. I am not planning to take it into the Allison shop at this point in time. Does this sound correct?

Thank you.

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