Allison 3500 fault

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Allison 3500 fault

October 04, 2013, 09:34:56 pm

I've encountered a shifting problem the last couple days. It's always at low speed in first gear making a sharp turn. There's a hard shift and the Allison ends up in neutral with the selected gear window flashing. I was finally in a position these evening when I could check for fault codes and got 3500 at D1, which the manual says is Power Interruption. I unplugged and replugged the three electric cables at the Allison CPU. Is there anything else I should do before I hit the road in the morning?

Re: Allison 3500 fault

Reply #1 – October 05, 2013, 11:08:21 am

Brett,

Did the shift panel go to "snake eyes"?

There are two power leads to the Allison ECU. The "memory" power which goes through a 5 amp fuse.

The other one, and the power lead that is suspect is the one supplied by the ignition solenoid since it is only hot when the ignition is on. Any other "ignition hot" issues-- dash HVAC fan continue to work as it should?

The other Brett

Re: Allison 3500 fault

Reply #2 – October 06, 2013, 07:29:56 pm

Brett,

I hadn't noticed any other actions when the tranny died before, but today I did. Everything was fine all day until I turned into our site for the night. I remember what looked like a snowflake where the shift number should be. All the dash gauges flashed and the HVAC quit momentarily. Would the ignition solenoid behave this way?

The other Brett

Re: Allison 3500 fault

Reply #3 – October 06, 2013, 07:49:30 pm

When I had similar problems with my transmission it turned out the altenator was shot.

Start the generator to see if the problem goes away.

best, paul

Re: Allison 3500 fault

Reply #4 – October 06, 2013, 08:11:24 pm

Brett,

In a word, YES.

But, easy to diagnose.

With ignition off, identify the large lug on the ignition solenoid that does not have power. Hook up a voltmeter to it.

If symptoms appear, check voltage. If no voltage, one of two issues-- either the ignition solenoid is failing, or the ignition switch/wiring from ignition switch is dropping.

If voltage at the "out" lug drops causing this, next step is to see if the signal terminal is loosing 12 VDC or if the solenoid is failing.

So, hook up the voltmeter to the signal terminal. If you have two voltmeters, or a voltmeter and test light, you can monitor both at the same time.

Now, if this happens and you need to keep moving, the "work around" is to LABEL all the wires on one of the large lugs and move them to the other large lug. In essence, you have done what the ignition solenoid does-- transmit power from one large lug to the other.

Other option is to just replace the ignition solenoid with an upgraded version. Here is the one I use:

Blue sea 9012 250-amp ignition solenoid.

L Solenoid - 12/24V DC 250A - Blue Sea Systems

Brett

Re: Allison 3500 fault

Reply #5 – October 07, 2013, 08:53:40 am

That surprises me. I've never had a solenoid fail intermittently this way. There is no way I can check voltages as you suggest unless I permanently install two volt meters. The hiccups have never lasted more than two seconds, always at the end of a day's drive, in first gear, making a tight turn. I'll go ahead and replace the ignition solenoid anyway.

Re: Allison 3500 fault

Reply #6 – October 12, 2013, 07:11:41 am

Last night the Cummins ECM threw a Speed Sensor Fault. Could this be connected to the Allison problem? Should I head for Cummins, Allison, or FT?

Re: Allison 3500 fault

Reply #7 – October 12, 2013, 07:47:02 am

Brett, I had a speed sensor fault. It it gets bad enough the Allison will stop shifting. Mine was caused by a rear main seal leaking a little and it fell on the sensor. The sensor is easy to change out but the why is the hard part. I took my coach to Allison they changed the sensor and the seal. I could have changed the sensor but not the seal so it was good I went.

Re: Allison 3500 fault

Reply #8 – October 12, 2013, 09:11:52 pm

The coach stopped shifting when I was halfway into my site at Rainbow's End. At least my power cord reached the pedestal. Anne heard sparking around the tag axle. It's dark and pouring rain now. Tomorrow I'll crawl underneath. From your description, John, the speed sensor must be on the bell housing, right?

Re: Allison 3500 fault

Reply #9 – October 12, 2013, 10:13:40 pm

Brett,

There are actually two speed sensors-- both external to the transmission and easy to access/replace/ etc.

But, before doing that, check that the connections from then are clean and tight-- they live in a dirty, wet environment.

Take some electrical cleaner under with you.

But, I would look for another source for the sparking. I can't access any documentation right now, but the speed sensors are NOT high amp sources for sparking.

The other Brett

Re: Allison 3500 fault

Reply #10 – October 12, 2013, 10:55:22 pm

Given intermittant ECM/TCM problems and sparking noise, I would be looking for a power connection problem. Bad/loose ground strap from engine / trans block to chassis, connections that get stretched/moved when the rear axle/tag shifts, etc. Allison TCMs are known to be sensitive to low voltage.

Re: Allison 3500 fault

Reply #11 – October 12, 2013, 11:35:25 pm

The "bad connection" suggestions sound plausible based on our experience. The Allison 3060 on our SOB went to "limp mode" with a speed sensor fault while we were driving on icy roads in blizzard conditions (dangerous operation as a result of some poor choices). Ice had built up on the cable and pulled it from the socket. Solution: thaw/dry cables with a hair dryer and plug it back in.

Re: Allison 3500 fault

Reply #12 – October 15, 2013, 09:20:23 pm

It was all my fault. I had added a second positive battery cable this summer to try to improve starting performance. I used flexible welding cable, and didn't tie it down enough. In the heat of this fall's driving, on section sagged enough to make contact with a pot on the driver's side tag brake and eventually wore through the insulation. Every time I made a sharp low speed turn the coach tilt would cause a momentary short to ground, dropping battery voltage and causing the Allison fault. I'm just sorry I have to admit my own stupidity.

Re: Allison 3500 fault

Reply #13 – October 15, 2013, 10:47:17 pm

D'oh!

Thanks for confirming your humanity. We refer to those events as "self inflicted wounds." Fortunately, it was an inconvenience rather than a show stopper. Nice detective work!

Re: Allison 3500 fault

Reply #14 – October 15, 2013, 11:46:36 pm

Brett we all make mistakes but at least this one got some brains going and we all shared in the "learning curve" of what may cause something like this to happen. So, it actually was a good thing in my opinion, now I know what may cause this to happen (should it ever do so )
John H

Re: Allison 3500 fault

Reply #15 – October 16, 2013, 10:05:21 am

Brett, Welcome to the club. I have been fortunate that my mistakes at least have not killed me or anyone else.

And..... All of us here now know that a LIBERAL application of wire ties can save a lot of trouble.
Glad you found it.
Gary B

Re: Allison 3500 fault

Reply #16 – November 21, 2020, 10:29:20 am

I'm having similar problems. Intermittently, as I'm slowing, the transmission will slam into 1st gear. Other times, I'll get the flashing gear indicator and the transmission shifts into neutral (once when turning right on a freeway onramp). When this happens, I cannot put the transmission into gear unless I push the up and down arrows simultaneously, then select D.

My error codes are:
d1 - 2214
d2 - 6933
d3 - 3500

I was ready to package up the ECU and shifter and send them to Transmission Instruments, but perhaps it could be a power/wiring issue. I am just handy enough to screw everything up if I attempt a repair. Should I take it to Stewart and Stevenson (60 miles away), or leave it in the driveway and send the ECU in for repair?

Re: Allison 3500 fault

Reply #17 – November 21, 2020, 11:32:16 am

moodmeister,

Please tell us what coach or what transmission you have!!!

Certainly you will want to verify both 12 VDC feeds to the Allison ECU as well as ground are good and 12+ VDC when this occurs before proceeding.

When we know what coach you have we can tell you where the fuses/breakers are.

Re: Allison 3500 fault

Reply #18 – November 21, 2020, 11:56:45 am

Quote from: moodmeister – November 21, 2020, 10:29:20 am

My error codes are:
d1 - 2214 (engine speed sensor)
d2 - 6933 (central operating processor timeout)
d3 - 3500 (power interruption)

Allison Transmission Codes Manual

Well, the good news: you are not seeing the 69-32 KISS OF DEATH fault code!

Your stored codes certainly seem to be, at least, power related.

Since failure is intermittent, that might also suggested a possible wiring or connector problem.

Try, to the best of your ability, the trouble shooting steps (link below). If no luck there, give John Kopalek a call and pick his brain.

Troubleshooting

Re: Allison 3500 fault

Reply #19 – November 21, 2020, 03:44:35 pm

Oops! Yes...of course, I did not post the pertinent information

Coach: 2002 U 295, build number 5973
Engine: Cummins ISL-400 (rebuilt at great expense)
Transmission: Allison 3000 MH 6 speed with retarder and WTEC-III Controls SN 6510310525

Where are the associated fuses and breakers?

Randy

Re: Allison 3500 fault

Reply #20 – July 31, 2021, 02:45:18 pm

Problem Solved.

I went to a local shop and the wires to the Allison ECU were corroded. Once cleaned, everything was good, for about 100 miles or so. The slamming shifting problem resumed.

I took the coach to Foretravel for its usual pilgrimage for yearly maintenance and they did their own troubleshooting. They diagnosed a faulty speed sensor. Since replacing this part, it's shifting perfectly again.

Randy

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