jlynn37064 Posted June 1 Share Posted June 1 2006 Beaver PT with 6 speed Allison. Only 33,000 miles. My speedometer is racing up and down immediately after I start the engine. The check trans light is on. I can move my rig. Motorhome has been stored under cover since Thanksgiving. The chassis batteries were dead. I charged them and then this issue with check trans occurred. I’ve unplugged the trans sensors and reconnected them. The check trans light went out but came back on. At no time would the transmission go into gear. The speedometer is racing and the odometer is racking up 10ths of a mile every few seconds. I disconnected the old batteries for 36 hours and then installed new batteries. This did not correct the issue. Please offer suggestions. Thanks IMG_2449.mov Link to comment Share on other sites More sharing options...
DavidL Posted June 1 Share Posted June 1 (edited) You will need to get the diagnostic codes from the transmission / engine to figure out what next to do. The Allison trans there are buttons to push and the shift console will blink with a code you can look up. If there is an engine issue, you will need a compatible Scan tool hardware and software to get the Diagnostic Trouble Codes (DTCs) Start there. You can google how to do the above. Edited June 1 by DavidL Link to comment Share on other sites More sharing options...
Dr4Film Posted June 1 Share Posted June 1 (edited) With the ignition on, to get the Allison into Diagnostic mode you push the up and down arrows TWICE. The first code should be displayed. To get to any additional codes you push the mode button each time to get to any those codes. It is possible that a bad ground wire in your dash is causing the gauge problems. Edited June 1 by Dr4Film 1 Link to comment Share on other sites More sharing options...
jlynn37064 Posted June 1 Author Share Posted June 1 (edited) Thank you both. I was able to get two codes. P0722 and P0880. I’ve goggled both of these. I’d like to check to connections to the TCM. Any suggestions as to where it would be located? Is on on the transmission? I cleared the codes and only P0722 returned Edited June 1 by jlynn37064 Link to comment Share on other sites More sharing options...
Tom Cherry Posted June 1 Share Posted June 1 6 minutes ago, jlynn37064 said: Thank you both. I was able to get two codes. P0720 and P0880. I’ve goggled both of these. I’d like to check to connections to the TCM. Any suggestions as to where it would be located? Is on on the transmission? WITH MONACO??. Have you looked in the Chassis Electrical Section of your manual. Many have the FRB layout and “mark” the TCM. It WILL BE UPFRONT. 90% on that. If is often in the FRB or maybe one bay back…in the ceiling …yes..either in or above the ceiling panel. I just looked at a 2014 Dynasty manual. Go to the chassis electrical….that gives you a visual….they are close to the same. You can google Allison MH3000/4000 TCM image. That’s one way to figure out what you are looking for…looks like BTW….Call ALLISON TECH SUPPORT….they are good and user friendly… 1 Link to comment Share on other sites More sharing options...
jlynn37064 Posted June 1 Author Share Posted June 1 Thanks Tom Link to comment Share on other sites More sharing options...
Benjamin Posted June 1 Share Posted June 1 772 is output speed sensor, which confirms the obvious at this point. And 880 is TCM input that seems like it could be the speed sensor, or the power supply voltage low, which you obviously had also, and since this code didn't return I'd ignore it for now. Since you unplugged the sensors, you're not afraid to get dirty, remove the output sensor and clean it. If that fails, see if the output is the same as the input speed sensor and swap them. Also, check the wiring from the output sensor to the main harness for chaffing, cracks, rodent damage, etc. Link to comment Share on other sites More sharing options...
Dr4Film Posted June 1 Share Posted June 1 Here are two Allison Fault Code Lists that I had in my files. Allison Trans Codes.pdf Allison Transmission 3000,4000 series fault code list updated.pdf 2 Link to comment Share on other sites More sharing options...
timaz996 Posted June 1 Share Posted June 1 Thanks for posting those Richard. Link to comment Share on other sites More sharing options...
jlynn37064 Posted June 2 Author Share Posted June 2 Benjamin, thanks for the suggestion of looking at the input sensor. It is the same sensor. I swapped them but still receiving the same code. The Check Trans light goes out when I unplugged and reconnect the output sensor. I can start the engine and select DRIVE and nothing happens. When I select REVERSE the check trans light comes on. I removed the wiring loom and inspected the wires. I found no visible issues. Someone suggested that the blue ground wire coming off one of the sensors can be an issue. Are you familiar with this wire? Link to comment Share on other sites More sharing options...
Benjamin Posted June 2 Share Posted June 2 (edited) I am not familiar with that blue wire. The only thing I'd have left to check are transmission instrument's troubleshooting directions on their website, which may not apply to your 2006, but worth a check. And an allison manual which I've found online for the older model allison, the manual has detailed directions for diagnosing based on symptoms, and also wire resistance checks. There is a ton of info on forums, just hard to find the right question. Since it's been a while since it ran, I'd find the transmission "brain" and check it for rodent damage, condensation, loose connections, whatever. Maybe even warm it up with a hair dryer? Edited June 2 by Benjamin Link to comment Share on other sites More sharing options...
jlynn37064 Posted June 2 Author Share Posted June 2 Thanks Benjamin Link to comment Share on other sites More sharing options...
Dr4Film Posted June 2 Share Posted June 2 If you have thoroughly cleaned the connector for the Output Speed Sensor than I would replace it. 1 Link to comment Share on other sites More sharing options...
jlynn37064 Posted June 2 Author Share Posted June 2 I found this on another website. It’s interesting that there are specifics on how many twist jn the sensor wire. https://dtctruck.com/product/allison-3000-4000-gen-4-fault-code-p0722-output-speed-sensor-circuit-no-signal/ Link to comment Share on other sites More sharing options...
Benjamin Posted June 2 Share Posted June 2 Very interesting. Lots of possible causes, but not that many that would happen in storage. You're getting this code standing still immediately on start up, and there's only one thing that sets this code (800RPM change in 2 seconds) so the TCM is obviously reading AC frequency, and it's not from the stationary signal wheel, probably not from the sensor (you tried both), it could be an internal TCM failure that's above my pay grade, or any wiring interference would have some AC source. The main AC source on a vehicle (assuming you've unplugged and turned off inverter and generator) is the alternator. You mentioned the batteries were dead, could be coincidence or could be leaky diodes that would also cause AC to be present in the DC. I'd measure the AC at the alternator B+ output, or even disconnect the small wires from the back of the alt, so it's not charging, depending on model. Not likely, but I don't know what else to try. Link to comment Share on other sites More sharing options...
jlynn37064 Posted June 30 Author Share Posted June 30 I did find the transmission control module. It was in the ceiling of the second pass through bay. There is an access panel but it only gave access to the leveling system. I had to remove the ceiling and was able to access the TCM. I did unplug and look for issues but found nothing. I’ve read post about a main ground cable but I didn’t see on is this bay. Is there a shop that will test and possibly rebuild my TCM? Link to comment Share on other sites More sharing options...
Tom Cherry Posted Sunday at 05:53 PM Share Posted Sunday at 05:53 PM 1 hour ago, jlynn37064 said: I did find the transmission control module. It was in the ceiling of the second pass through bay. There is an access panel but it only gave access to the leveling system. I had to remove the ceiling and was able to access the TCM. I did unplug and look for issues but found nothing. I’ve read post about a main ground cable but I didn’t see on is this bay. Is there a shop that will test and possibly rebuild my TCM? Here’s where it get’s tricky. There is no record, unless printed (supposedly) on a label or on the cover of the TCM as to the “programming” parameters. The shift points were determined (sometimes more of the “seat of the pants”) or “SET my Monaco. Each year, Allison, Monaco and the Engine supplier….their “tech reps” would review the shift points for PERFORMANCE and ECONMY modes. Usually just a carryover, unless Monaco changed the rear differential ratio. NO RECORDS of this, by model exist. Allison says…. WE APPROVED…but Monaco never supplied us with them. Monaco ordered the TCM’s and sent them to a local (presumably Allison) shop to be programmed. I TRIED both Allison and Monaco….BRICK WALL…response….label or marked on the TCM…not in our data base. SO….at this point….your best approach may be to get an Allison certified shop involved. They might fix the issue. You do NOT want someone “messing” around or doing unimaginable “things” to the TCM. If a TCM fails, the best hope….a dealer can read the parameters and reprogram….otherwise it is PURE GUESS. Now, if you know, exactly the level, medium acceleration shift point is for every upshift and downshift….then you could tell the tech. BUT the data was Monaco supplied was never published. For example… the normal Up SHIFT for my tranny…either performance or economy is around 62 MPH…5 to 6. BUT…the downshift point in performance is about the same. It also upshifts around that in economy. But, in economy, it will drop as low as 56 MPH for the downshift. I know that from a LOT of observations and testing. I have NO IDEA how that is “programmed” inside the TCM. IF your TCM is toast….then you need to find a willing partner with the same engine, year, model, and REAR END ratio. They will have to go to an Allison shop for a program scan and download. You pay for that. They then have the critical data…free… . Link to comment Share on other sites More sharing options...
jacwjames Posted Sunday at 08:08 PM Share Posted Sunday at 08:08 PM (edited) In 2013 my wife was getting ready to head out on a trip. I took the coach and filled it up and parked it in front of the house on the street so I could hook up the toad. After the toad was hooked up I was going to check the lights/brakes. Went to start the rig and nothing, the rig won't start and the transmission display had snake eyes on it. For two days I checked everything I could check and finally called the Allision shop ~30 miles away and asked if they could send a tech out>>nope, nada, not a chance. They said they were short handed and I'd have to have the rig towed to their shop. So arranged for a tow, the truck was coming into the subdivision while I was driving out headed to airport/Spain. Wife took over and made sure the coach got towed to the shop. Shop diagnosed a bad TCM, they didn't have one but one of their other shops did, ~100 miles away. To expedite the process my wife went and got the TCM and delivered it to the shop where the coach was at. They had to copy the programming from the old TCM but got the rig going in short order. Cost $3600. I kept the old TCM just because and last year decided to look at the guts. Obvious there was a problem, large burnt/melted spot on the circuit board. I guess I could have looked inside, probably would have saved a couple days of me looking for the problem. It was pretty obvious. Wife barely made it to the dog show in NY Finger Lakes area, pulled into the parking lot and handed her dog to a handler who volunteered to take it into the ring. Can't remember if it won or not. Edited Sunday at 08:08 PM by jacwjames Link to comment Share on other sites More sharing options...
jlynn37064 Posted Sunday at 11:06 PM Author Share Posted Sunday at 11:06 PM I just removed the TCM. It was hot, about 120 degrees. I am now thinking it has a short of some kind. I’m going to check around for a replacement. Link to comment Share on other sites More sharing options...
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